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As far as I understand, various abilities like flying, sight, hearing etc. were caused by slow evolution, where those with a greater ability to to these things had better chance of survival. (If this assumption is wrong, then I am happy to delete this question).
Are there, however, any documented examples of by evolutionary leaps being made, over the course of just a few generations? I understand, that some abilities have a tipping point where one gets the ability suddenly, but there is not a lot of physiological change made. An example of this would be the ability to climb a tree, which could suddenly be possible if the body weight is reduced with just a few percent. What my question is about, are sudden changes to the characteristics of a creature.
@kmm and @shigeta provided you with a nice observational account of sudden leaps in large organisms. However, if you want to look at where this is the norm and try to build a mathematical theory then you need to look at something much smaller; the prime candidate is affinity maturation.
In the human immune system, when exposed to an antigen B cells produce antibodies. If it is your first exposure to the antigen then the antibodies produced will probably have very low binding affinity. However, after some exposure time, your B cells will start to produce antibodies with much higher affinities for the antigen and thus you will be able to better fight off the disease. The cool part, is that the antigen produced is tuned via an evolutionary process!
There is differential survival, with only antibodies with the highest affinity being able to survive. Variability is introduced by a very high mutation rate in the complementarity determing region (CDR). (Tonegawa, 1983). The length of this evolutionary process is very short, typically a local equilibrium is found after only 6-8 nucleotide changes in CDR (Crews et al., 1981; Tonegawa, 1983; Clark et al., 1985), so you need only a few point mutations to quickly develop a drastically better tuned antibody.
The standard mathematical model for this is Kauffman's NK model. With a protein sequence on $N$ sites, we say that evolution is fast (and we have a sudden leap) if after our fitness landscape changes, we can get to a new local equilibrium in a number of generations that scales with $log N$. Kauffman & Weinberger (1989) showed how this model can be used to study affinity maturation, and showed that to achieve a sudden leap we need high epistasis and low correlations between pointwise mutants. In particular, their model suggests that typical epistasis in the CDR is on the order of 40 proteins (out of the total 112 proteins in the CDR).
Clark, S.H., Huppi, K., Ruezinsky, D., Staudt, L., Gerhard, W., & Weigert, M. (1985). Inter- and intraclonal diversity in the antibody response to influenza hemagglutin. J. Exp. Med. 161, 687.
Crews, S., Griffin, J., Huang, H., Calame, K., & Hood, L. (1981). A single V gene segment encodes the immune response to phosphorylcholine: somatic mutation is correlated with the class of the antibody. Cell 25, 59.
Kauffman, S. and Weinberger, E. (1989) The NK Model of rugged fitness landscapes and its application to the maturation of the immune response. Journal of Theoretical Biology, 141(2): 211-245
Tonegawa, S. (1983). Somatic generation of antibody diversity. Nature 302, 575.
Zuk et al. (2006) document the rapid evolution of song-less crickets in a population of crickets that previously used song for courtship.
In less that 20 generations, over 90% of male crickets of the species Teleogryllus oceanicus evolved to a novel morphology ("flatwing") that rendered them unable to call to females. They hypothesize that this shift resulted from the presence of an North American invasive "acoustically orienting parasitoid fly."
Basically the flies detect calling males and parasitize them, rendering them unable to reproduce. Were it not for the presence of the parasitoid fly, the flatwing flies would likely not have survived. Non-calling individuals rely on the presence of calling males to bring females near for mating.
The ability to drink milk by the inheritance of lactase persistence via a single allele change. Sociology and genetic studies have shown that the immigration of a few lactose tolerant people into large non-lactose tolerant populations, the lactase persistence gene quickly spreads through the population, a sign of a dominant mutation and survival of the fittest at work.
Not in the mood to dissect the papers but here are a few commentaries:
I think that this might refer to evolution in punctuated equilibrium as described by Stephen Gould et al way back in the 70s. If this is the case, it refers more to the idea that changes and speciations can be quite rapid in time and for long periods you don't see morphological changes or speciation events in the record.
If so, then this is influenced by the study of evolution in cases where there are large changes in the environment very rapidly. The classic case is when there is a bare island and new animals arrive only rarely. This is all very much inspired by Darwin's observations in the Galapagos, but has since been studied quite a bit. In such cases you see just handful of sets of birds suddenly appear and you find a finch that can scrape bugs out of bark, another that can dig into narrow niches in the rock for food, where in a broader ecosystem two completely different species would be utilizing those 2 food sources.
It should be said that no evolutionary leap should be understood as an acceleration or deceleration of evolution. Only a change in the rate of adoption of variations because of a wider set of possible advantages those variations can represent.
With all due respect, a few of these answers, although good examples of selection at work, were voted too high given the specific question asked: “documented examples of by evolutionary leaps being made, over the course of just a few generations?”
Sometimes we're better being honest and identifying something as an 'unknown' or 'yet to be observed' than to list (and have people up-vote) poor examples. We do evolution a dis-service when we promote poor examples as answers to questions like these.
The cricket losing the ability to sing (communicate) examples does demonstrate mutation and natural selection at work, but really only shows the REDUCTION of a capability. It's not a good example of evolutionary leaps. It only happens to be beneficial in one SPECIFIC context. This would be analogous to tanks on a battle-field which communicate via radio, vulnerable to radio-frequency tracking missiles. Any tank with a broken radio would not be vulnerable to these missiles. Although technically 'beneficial' in this context, it's an example of a loss of capability, not a gain of capability. We need to promote examples of mutations that PRODUCE capabilities.
Lactase persistence example likewise is an example of mutation and natural selection, but not a good example of a GAIN in functionality (as some have pointed out in the comments). It's technically the loss of the normal switching-off mechanism of lactase production following weaning. So once again, a loss, that happens to have a beneficial side-effect.
Regarding punctuated equilibrium, I'm not surprised that was mentioned but was surprised that it got some votes. It's a hypothetical explanation for why we see gaps in the fossils, but not conclusive 'evidence', or in the case of the question asked not “documented examples”.
Again: We do evolution a dis-service when we promote poor examples as answers to questions like these. Let's focus on quality, not quantity when it comes to presenting evidence for evolution.
The Concept of Co-option: Why Evolution Often Looks Miraculous
Darwin believed that evolution generally occurred through a series of small, gradual changes. This proposal was counter-intuitive to many people because it seemed likely that “transitional” forms would not survive. Darwin, and later Cuènot, recognized that this problem was easily solved if characters that had evolved for one reason changed their function at a later time with little to no concurrent structural modification, at least initially. In other words, traits that had evolved under one set of conditions were co-opted to serve a different function under a second set of conditions. This meant that organisms carried with them in the structures of their genes, proteins, morphological, physiological, and behavioral characters the potential for rapid evolutionary change, so rapid, indeed, that the process looked miraculous and Lamarckian. In this paper, I discuss some of the paradigm examples of co-option, from genes to behavior.
Darwin believed that evolution generally occurred through a series of small, gradual changes. Oftentimes, though, it appears that evolution has leapt over many of the intermediate forms to arrive rapidly at a later, fully formed stage. These leaps look almost miraculous in retrospect, attributable more to Lamarckian than Darwinian mechanisms (e.g., animals needed jaws, so they grew them). In the following essay, I shall discuss how various researchers have tried to solve the problem of these evolutionary leaps within a Darwinian framework. This shall involve traveling a long road beginning with Darwin himself and continuing through to the present day. Along the way we will encounter three terms: preadaptation, exaptation, and co-option. No other terminology is needed for the journey.
The Quote Mine Project
"Paleontologists have paid an enormous price for Darwin's argument. We fancy ourselves as the only true students of life's history, yet to preserve our favored account of evolution by natural selection we view our data as so bad that we almost never see the very process we profess to study. . The history of most fossil species includes tow [sic] features particularly inconsistent with gradualism: 1. Stasis. Most species exhibit no directional change during their tenure on earth. They appear in the fossil record looking much the same as when they disappear morphological change I [sic] usually limited and directionless. 2. Sudden appearance. In any local area, a species does not arise gradually by the steady transformation of its ancestors it appears all at once and 'fully formed.'" (Gould, Stephen J. The Panda's Thumb , 1980, p. 181-182)
Snipped in the ellipsis is:
"We believe that Huxley was right in his warning. The modern theory of evolution does not require gradual change. In fact, the operation of Darwinian processes should yield exactly what we see in the fossil record. It is gradualism we should reject, not Darwinism."
Following this passage is:
"Evolution proceeds in two major modes. In the first, phyletic transformation, an entire population changes from one state to another. . The second mode, speciation, replenishes the earth. New species branch off from a persisting parental stock.
"Darwin, to be sure, acknowledged and discussed the process of speciation. But he cast his discussion of evolutionary change almost totally in the mold of phyletic transformation. In this context, the phenomenon of stasis and sudden appearance could hardly be attributed to anything but imperfection of the record for if new species arise by transformation of entire ancestral populations, and if we almost never see the transformation (because species are essentially static through their range), then our record must be hopelessly incomplete.
"Eldredge and I believe that speciation is responsible for almost all evolutionary change. Moreover, the way in which it occurs virtually guarantees that sudden appearance and stasis shall dominate the fossil record." to p183 .
A more complete citation would be: Gould, Stephen Jay 1980. "The Episodic Nature of Evolutionary Change" The Panda's Thumb . New York: W. W. Norton & Co., p. 181-182.
"Paleontologists are traditionally famous (or infamous) for reconstructing whole animals from the debris of death. Mostly they cheat. . If any event in life's history resembles man's creation myths, it is this sudden diversification of marine life when multicellular organisms took over as the dominant actors in ecology and evolution. Baffling (and embarrassing) to Darwin, this event still dazzles us and stands as a major biological revolution on a par with the invention of self-replication and the origin of the eukaryotic cell. The animal phyla emerged out of the Precambrian mists with most of the attributes of their modern descendants." (Bengtson, Stefan, "The Solution to a Jigsaw Puzzle," Nature , vol. 345 (June 28, 1990), pp. 765-766)
This is from an article that summarizes the finding of a peer-reviewed paper elsewhere in the issue, which reports on the discovery of complete specimens of halkieriids, a now extinct taxon from the Early Cambrian period:
Palaeontologists are traditionally famous (or infamous) for reconstructing whole animals from the debris of death. Mostly they cheat. Even extinct beasts such as dinosaur have scores of living relatives (birds, mammals, reptiles) that make reconstructions 'simply' a matter of competent comparative anatomy. But how do you go about the job when there seem to be no close living relatives on which to base the model? This is a problem particularly when dealing with organisms that derive from the 'Cambrian explosion'.
If any event in life's history resembles man's creation myths, it is this sudden diversification of marine life when multi-cellular organisms took over as the dominant actors in ecology and evolution. Baffling (and embarrassing) to Darwin, this event still dazzles us and stands as a major biological revolution on a par with the invention of self-replication and the origin of the eukaryotic cell. The animal phyla emerged out of the Precambrian mists with most of the attributes of their modern descendants. But nature is wasteful. Most species never give rise to anything, and present-day phyla derive from a lucky minority. Many of the not-so-lucky fossil species may also be comfortably classified in these same living phyla, but it is a feature of many Cambrian assemblages that they contain a large proportion of forms that cannot be so treated.
We can see from the context that "cheating" is just a case of making use of comparative anatomy. Since in most cases soft tissue isn't preserved, it's not unreasonable to make informed assumptions about the placement and size muscles and such. But how does one reconstruct a creature that has no living relatives?
It should also be emphasized that the writer states that "If any event in life's history resembles man's creation myths" (emphasis added). And obviously it's not that much of a resemblance. These new "organisms took over as the dominant actors in ecology and evolution" (emphasis added). This wasn't creation from nothing, otherwise there would be no organisms to take over from.
The paragraphs preceding above quote:
"An extraordinary discovery by Conway Morris and Peel, described on page 802 of this issue, answers the prayers of many palaeontologists. The authors report complete specimens of halkieriids from 550-million-year-old Early Cambrian rocks in northern Greenland.
Those unfamiliar with halkieriids may be excused. The first fragment was unearthed in Bornholm in the Baltic area in the 1960s, and it took some time before palaeontologists realized that they were dealing with isolated dermal scales (sclerites) of a previously unknown type of animal. There are no halkieriids alive today yet in their short time they were highly successful and filled the Earth's seas.
Palaeontologists are traditionally famous (or infamous) for reconstructing whole animals from the debris of death. Mostly they cheat.
Even extinct beasts such as dinosaurs have scores of living relatives (birds, mammals, reptiles) that make reconstructions 'simply' a matter of competent comparative anatomy. But how do you go about the job when there seem to be no close living relatives on which to base the model ? This is a problem particularly when dealing with organisms that derive from the 'Cambrian explosion'.
So the phrase 'mostly they cheat' refers to using living relatives of fossil taxa to reconstruct them.
If any event in life's history resembles man's creation myths, it is this sudden diversification of marine life when multicellular organisms took over as the dominant actors in ecology and evolution. Baffling (and embarrassing) to Darwin, this event still dazzles us and stands as a major biological revolution on par with the invention of self-replication and the origin of the eukaryotic cell. The animal phyla emerged out of the Pre-Cambrian mists with most of the attributes of their modern descendants.
The next part snipped out :
But nature is wasteful. Most species never give rise to anything, and present-day phyla derive from a lucky minority. The not-so-lucky fossil species may also be comfortably classified in these living phyla, but it is a feature of many Cambrian assemblages that they contain a large proportion of forms that cannot be so treated. In the 1970s, the realization started to grow that there poorly understood forms may indicate a great diversity of high-level taxa.
"Modern multicellular animals make their first uncontested appearance in the fossil record some 570 million years ago - and with a bang, not a protracted crescendo. This 'Cambrian explosion' marks the advent (at least into direct evidence) of virtually all major groups of modern animals - and all within the minuscule span, geologically speaking, of a few million years." (Gould, Stephen J., Wonderful Life: The Burgess Shale and the Nature of History , 1989, p. 23-24)
A short while later, in the same paragraph, he says:
"Our fossil record is almost exclusively the story of hard parts. But most animals have none, and those that do reveal very little about their anatomies in their outer coverings (what could you infer about a clam from its shell alone?). Hence, the rare soft-bodied faunas of the fossil record are precious windows into the true range and diversity of ancient life."
"The fossil record had caused Darwin more grief than joy. Nothing distressed him more than the Cambrian explosion, the coincident appearance of almost all complex organic designs. " (Gould, Stephen J., The Panda's Thumb , 1980, p. 238-239)
"His opponents interpreted this event as the moment of creation, for not a single trace of Precambrian life had been discovered when Darwin wrote the Origin of Species . (We now have an extensive record of monerans from these early rocks, see essay 21)"
"The majority of major groups appear suddenly in the rocks, with virtually no evidence of transition from their ancestors." (Futuyma, D., Science on Trial: The Case for Evolution , 1983, p. 82)
Ironically, Futuyma immediately follows this with the observation of an early example, by Gish, of quote mining. A little later he says:
"The transitional forms that evolve so quickly, and in such a small area, are very unlikely to be picked up in the fossil record. Only when the newly evolved species extends its range will it suddenly appear in the fossil record. Eldredge and Gould have suggested, therefore, that the fossil record should show stasis, or equilibrium, of established species, punctuated occasionally by the appearance of new forms. Hence, the fossil record would be most inadequate exactly where we need it most -- at the origin of major new groups of organisms." p. 83
"Most families, orders, classes, and phyla appear rather suddenly in the fossil record, often without anatomically intermediate forms smoothly interlinking evolutionarily derived descendant taxa with their presumed ancestors." (Eldredge, Niles, Macro-Evolutionary Dynamics: Species, Niches, and Adaptive Peaks , 1989, p. 22)
"In spite of these examples, it remains true, as every paleontologist knows, that most new species, genera, and families, and that nearly all new categories above the level of families, appear in the record suddenly and are not led up to by known, gradual, completely continuous transitional sequences." (Simpson, George Gaylord, The Major Features of Evolution , 1953, p. 360)
The two paragraphs above the one containing the mined bit will help establish the context a bit better, I think. Sorry for the length.
"The chances that the remains of an organism will be buried, fossilized, preserved in the rock to our day, then exposed on the surface of dry land and found by a paleontologist before they disintegrate are extremely small, practically infinitesimal. The discovery of a fossil of a particular species, out of the thousands of millions that have inhabited the earth, seems almost like a miracle even to a paleontologist who has spent a good part of his life performing the miracle. Certainly paleontologists have found samples of an extremely small fraction, only, of the earth's extinct species, and even for groups that are most readily preserved and found as fossils they can never expect to find more than a fraction.
"In view of these facts, the record already acquired is amazingly good. It provides us with many detailed examples of a great variety of evolutionary phenomena on lower and intermediate levels and with rather abundant data that can be used either by controlled extrapolation or on a statistical sampling basis for inferences as to phenomena on all levels up to the highest. Among the examples are many in which, beyond the slightest doubt, a species or genus has been gradually transformed into another. Such gradual transformation is also fairly well exemplified for subfamilies and occasionally for families, as the groups are commonly ranked. Splitting and subsequent gradual divergence of species is also exemplified, although not as richly as phyletic transformation of species (no doubt because splitting of species usually involves spatial separation and paleontological samples are rarely adequate in spatial distribution). Splitting and gradual divergence of genera is exemplified very well and in a large variety of organisms. Complete examples for subfamilies and families are also known, but are less common.
"In spite of these examples, it remains true, as every paleontologist knows, that most new species, genera, and families and that nearly all new categories above the level of families appear in the record suddenly and are not led up to by known, gradual, completely continuous transitional sequences. When paleontological collecting was still in its infancy and no clear examples of transitional origin had been found, most paleontologists were anti-evolutionists. Darwin (1859) recognized the fact that paleontology then seemed to provide evidence against rather than for evolution in general or the gradual origin of taxonomic characters in particular. Now we do have many examples of transitional sequences. Almost all paleontologists recognize that the discovery of a complete transition is in any case unlikely. Most of them find it logical, if not scientifically required, to assume that the sudden appearance of a new systematic group is not evidence for special creation or for saltation, but simply means that a full transitional sequence more or less like those that are known did occur and simply has not been found in this instance."
"The gaps in the record are real, however. The absence of any record of any important branching is quite phenomenal. Species are usually static, or nearly so, for long periods, species seldom and genera never show evolution into new species or genera but replacement or one by another, and change is more or less abrupt." (Wesson, R., Beyond Natural Selection , 1991, p. 45)
Who is Robert Wesson? According to information gleaned from two web pages, From Bradford Books: Beyond Natural Selection and Robert G. Wesson, Political Science: Santa Barbara, he was a political scientist who died in 1991, the year this book was published. [Fuller quote follows:]
"The impression that many groups arise suddenly at about the same time may be exaggerated by the system of classification. As one traces different orders, such as carnivores or ungulates, back to their earliest appearance, one naturally finds that the ancestral forms differ less than do their modern descendants. Similarly, it was possible for the principal animal types, the phyla, to diverge very rapidly, leaving no traces of intermediates, because they were much simpler and less deeply separated than their distant descendants. The differences, although basic, were not yet deeply embedded.
"The gaps in the record are real, however. The absence of any record of any important branching is quite phenomenal. Species are usually static, or nearly so, for long periods, species seldom and genera never show evolution into new species or genera but replacement of one by another, and change is more or less abrupt.
"This contradicts the Darwinian approach. Natural selection -- and Lamarckian evolution by use and disuse -- would imply gradual, progressive change, with randomly diverging lines of descent. This would make a great irregular bush, not the branching ideal tree of life, much less the record that we have, with big and little branches suspended without junctions.
"Those who study the fossil record, dealing not with equations of population genetics but with hard facts of the past, have been most inclined to be skeptical of Darwin's insistence on slow, more or less steady change. Such paleontologists as Stephen J. Gould, Niles Eldredge, and Steven M. Stanley have recently been in the vanguard of the critics."
The original quote is accurate, forms a complete paragraph, and seems to be discussing Punctuated Equilibria, but at the end a reference is also given, to page 307 of "The eukaryote genome in development and evolution" (John, B., & Miklos, G. L. G. 1988. London: Allen & Unwin).
In this latter book the section referred to discusses the Cambrian explosion and the Burgess Shale!
Wesson seems to be confused about what he is talking about in the paragraph quoted, and I'm not sure why I should take the musings of a political scientist as representative of current palaeontological thought.
- Jon (Augray) Barber and Mike Dunford
"All through the fossil record, groups - both large and small - abruptly appear and disappear. . The earliest phase of rapid change usually is undiscovered, and must be inferred by comparison with its probable relatives." (Newell, N. D., Creation and Evolution: Myth or Reality , 1984, p. 10)
This isn't on page 10. And the book doesn't have an index. I guess it's time to plow through the whole thing.
. . . And after reading the entire book, I can't find it anywhere.
"Paleontologists had long been aware of a seeming contradiction between Darwin's postulate of gradualism . and the actual findings of paleontology. Following phyletic lines through time seemed to reveal only minimal gradual changes but no clear evidence for any change of a species into a different genus or for the gradual origin of an evolutionary novelty. Anything truly novel always seemed to appear quite abruptly in the fossil record." (Mayr, E. Our [ sic ] Long Argument: Charles Darwin and the Genesis of Modern Evolutionary Thought , 1991, p. 138)
"During the synthesis it became clear that since new evolutionary departures seem to take place almost invariably in localized isolated populations, it is not surprising that the fossil record does not reflect these sequences."
The name of the book is really One Long Argument .
"The record certainly did not reveal gradual transformations of structure in the course of time. On the contrary, it showed that species generally remained constant throughout their history and were replaced quite suddenly by significantly different forms. New types or classes seemed to appear fully formed, with no sign of an evolutionary trend by which they could have emerged from an earlier type." (Bowler, Evolution: The History of an Idea, 1984, p. 187)
I only have the second edition, and this is on page 200f. But note what Bowler then says:
"Darwin devoted a chapter of the Origin to explaining the "imperfection of the fossil record," arguing that the fossils we discover represent only a tiny fraction of the species that actually have lived. Many species, and many whole episodes in evolution, will have left no fossils at all, because they occurred in areas where conditions were not suitable for fossilization. Apparently sudden leaps in the development of life are thus illusions created by gaps in the evidence available to us. Future discoveries may help to fill in some of the gaps, but we can never hope to build up a complete outline of the history of life."
"Instead of finding the gradual unfolding of life, what geologists of Darwin's time, and geologists of the present day actually find is a highly uneven or jerky record that is, species appear in the sequence very suddenly, show little or no change during their existence in the record, then abruptly go out of the record. and it is not always clear, in fact it's rarely clear, that the descendants were actually better adapted than their predecessors. In other words, biological improvement is hard to find." (Raup, David M., "Conflicts Between Darwin and Paleontology," Bulletin, Field Museum of Natural History , vol. 50, 1979, p. 23)
See, also, Troy Britain's "Feedback" article at Talk.Origins Archive: June 2001 Feedback
But on the previous page Raup writes:
We must distinguish between the fact of evolution -- defined as change in organisms over time -- and the explanation of this change. Darwin's contribution, through his theory of natural selection, was to suggest how the evolutionary change took place. The evidence we find in the geologic record is not nearly as compatible with darwinian natural selection as we would like it to be.
Note that Raup believes that evolution has occurred he calls evolution a "fact". And on page 25 he writes:
What appeared to be a nice progression when relatively few data were available now appears to be much more complex and much less gradualistic. So Darwin's problem has not been alleviated in the last 120 years and we still have a record which does show change but one which can hardly be look upon as the most reasonable consequence of natural selection. [Emphasis in original]
And later on the same page:
So natural selection as a process is okay. We are also pretty sure that it goes on in nature although good examples are surprisingly rare.
It should be obvious by now that what Raup is arguing against is not evolution, but gradual evolution in all cases.
"A major problem in proving the theory (of evolution) has been the fossil record the imprints of vanished species preserved in the Earth's geological formations. This record has never revealed traces of Darwin's hypothetical intermediate variants instead species appear and disappear abruptly, and this anomaly has fueled the creationist argument that each species was created by God." (Czarnecki, Mark, "The Revival of the Creationist Crusade", MacLean's , January 19, 1981, p. 56)
Is [the quote-miner] Canadian? This quote is from a Canadian newsmagazine, and would be relatively obscure outside of Canada. The quote has clipped off part of the last sentence, and some of the punctuation has changed:
A major problem in proving the theory has been the "fossil record," the imprints of vanished species preserved in the Earth's geological formations. This record has never revealed traces of Darwin's hypothetical intermediate variants - instead, species appear and disappear abruptly, and this anomaly has fueled the creationist argument that each species was created by God as described in the Bible.
Once again, this seems to be a glossing over of the controversy surrounding Punctuated Equilibrium. Given that many in the news media seem to have a superficial understanding of science, I'm not inclined to take the technical aspects of a news article about the evolution-creation controversy seriously, especially when I see a gem like this:
Essentially, Darwin stated that a species evolved by the random mutation of genes, which then produced variants of the original species.
The claim that Darwin knew about genes and mutation is news to me, as I'm sure it is to a lot of people. But Czarnecki does raise an interesting point. Discussing how some people view the difference between fact and theory, he writes:
Such a pedagogical approach, though initiated with the best of intentions, strips the corpus of scientific knowledge down to certain facts that can be perceived by the five senses with the aid of technology everything else is factually suspect because it cannot be directly "observed" - so much for paleontology (fossil study) and all of nuclear physics.
And a few sentences later:
What about history? Past events cannot be observed, records of them are just fallible memories, words - just like the Bible, in fact.
"Eldredge and Gould, by contrast, decided to take the record at face value. On this view, there is little evidence of modification within species, or of forms intermediate between species because neither generally occurred. A species forms and evolves almost instantaneously (on the geological timescale) and then remains virtually unchanged until it disappears, yielding its habitat to a new species." (Smith, Peter J., "Evolution's Most Worrisome Questions," Review of Life Pulse by Niles Eldredge, New Scientist , 1987, p. 59)
First of all, a complaint. "New Scientist" magazine is a weekly, so there are about 50 issues to check through, to find "page 59". I found this particular one in the 19 November 1987 issue (volume 116, number 1587).
It is a review by Peter J. Smith of Niles Eldredge's "Life Pulse." It seems to be an accurate quotation. Perhaps I should also note this additional sentence from the review:
"Using examples from throughout the fossil record, both marine and continental, Eldredge thus demonstrates convincingly that extinction is the motor of species evolution, and that, without it, there could be no development."
Again, though, this is a discussion of Punctuated Equilibrium and Eldredge's contention that speciation occurs "quickly" (in geologic terms) in small populations and that, if that is true, we would expect examples of "modification within species, or of forms intermediate between species" to be rare. Both he and Gould have noted, however, that they are not completely lacking and that examples of transitionals between higher taxonomic groups are even more common.
"The principle problem is morphological stasis. A theory is only as good as its predictions, and conventional neo-Darwinism, which claims to be a comprehensive explanation of evolutionary process, has failed to predict the widespread long-term morphological stasis now recognized as one of the most striking aspects of the fossil record." (Williamson, Peter G., "Morphological Stasis and Developmental Constraint: Real Problems for Neo-Darwinism," Nature , Vol. 294, 19 November 1981, p. 214)
Here Williamson reiterates and clarifies the points he was making in the paper quote mined in #55 (Williamson, P.G., Palaeontological Documentation of Speciation in Cenozoic Molluscs from Turkana Basin), once again discussing Punctuated Equilibrium.
But punctuated equilibrium is compatible with much current neo-Darwinian thought.
The principal argument in my paper is that when speciation events occur in the Turkana Basin mollusc sequence, they are invariably accompanied by major developmental instability.
So we can see that Williamson isn't criticizing evolution, or all of neo-Darwinism, but one aspect of it, namely gradualism.
"It is a simple ineluctable truth that virtually all members of a biota remain basically stable, with minor fluctuations, throughout their duration. " (Eldredge, Niles, The Pattern of Evolution , 1998, p. 157)
From Chapter 6, section titled "Enter Evolution"
"There are clear connections between these varying ecological patterns of resiliency, from the smallest scale of the individual organism, through ecological succession, to the even larger scale of habitat tracking. Individual organisms and, in the later two cases, entire species tend to survive by moving around, sending out propagules to rebuild ecosystems, whether locally degraded (Cercopia on El Yunque) or regionally revamped (as when glaciers slowly move south from the arctic). But evolution is classically about change. So far, local and regional patterns of ecological resiliency imply stability of individual species lineages, not evolutionary change. Where and how does real evolution come into the picture?
"Consider the effect of Hurricane Hugo on El Yunque, and on the entire island of Puerto Rico, for that matter. Prior to Hugo's hit in 1989, the endemic Puerto Rican parrot had been reduced to fewer than 100 known individuals living in the Loquillo Mountains, of which El Yunque is one. Agriculture and urbanization had already transformed so much of this bird species' habitat that it was on the verge of extinction. Hugo took about 50 percent of the remaining birds. Though the population has since recovered to approximately pre-Hugo proportions, and is now being augmented by a captive breeding program, Hugo might very well have done away with these beautiful animals entirely.
"In other words, physically induced ecological calamity, if great enough in a real scope and intensity, can drive all the populations of a species extinct. Indeed, it can drive many different species extinct all at the same time. And that's exactly what we paleontologists see in the fossil record as the dominant pattern, not only of extinction, but of evolution as well.
"It is not just single species that are in stasis. Virtually all the component species of regional ecosystems are evolutionarily stable, often for millions of years. Of course, that's only half the pattern. Periodically, the majority of those species disappear, to be replaced, in due course, by others. One way of looking at this pattern is to see it as the ecological generalization of stasis and change that underlies the notion of punctuated equilibria. It is a simple ineluctable truth that virtually all members of a biota remain basically stable, with minor fluctuations, throughout their durations. (Remember, by "biota" we mean the commonly preserved plants and animals of a particular geological interval, which occupy regions often as large as Roger Tory Patterson's "eastern" region of North American birds.) And when these systems change -- when the older species disappear, and new ones take their place -- the change happens relatively abruptly and in lockstep fashion. It affects most of the species in a region more or less at the same time. Evolution goes hand in hand with the degradation and rebuilding of ecosystems, and the origin of new species depends in large measure on the extinction of older species. [Eldredge, Niles 1999 The Pattern of Evolution W. H. Freeman and company, New York. Page 157-158.] [Emphasis in original.]
The section is about the ways in which biotic communities are stable, co-adapted, integrated systems, and that evolution is mainly a result of "turnover pulses" and coordinated stasis.
"But fossil species remain unchanged throughout most of their history and the record fails to contain a single example of a significant transition." (Woodroff, D.S., Science , vol. 208, 1980, p. 716)
This is a review of Steven Stanley's book Macroevolution .
"Darwin and most subsequent authors including G. G. Simpson have held that most evolutionary transitions occur within established lineages by phyletic gradualism guided by natural selection. But fossil species remain unchanged thoughout most of their history and the record fails to contain a single example of a significant transition. Similarly, it is difficult to account for the greatly accelerated pace of evolution during periods of adaptive radiation. An alternative model of evolution, that of punctuated equilibria, introduced by Niles Eldredge and Stephen Jay Gould in the early 1970s, more fully accounts for these same observations."
Sigh, yet another [punctuated equilibria] supportive quote taken out of context to fool people who don't know that there are varying "camps" as to evolution's actual mechanism. In case you haven't already guessed, that's what this quote is. The author is reminding that gradualist hypotheses for the mechanism of evolution have a hard time explaining the fossil record, while punctuated equilibrium hypotheses on evolutionary mechanisms make much more sense in light of the same fossil record.
This article is actually not a scientific paper in itself but rather a review by Woodroff of Steven Stanley's "Macroevolution. Pattern and Process" Freeman S.F. 1979 xii, 332 pp illus. $20 (wasn't it cool when you could get a book like this for $20.00?)
The first sentences of this article reads thus (brackets mine):
" Macroevolution [the book] is concerned with the origin and extinction of species and the diversification of lineages, or, turning the problem around with how key morphological and functional features of a lineage evolve. One of the major debates in biology concerns the role of micro-evolutionary forces (natural selection, genetic drift and mutation) at the trans-species level. Are the major changes in the history of life attributable to speciation or to the gradual transformation of lineages within established species by microevolutionary forces?"
I'd like to note that this book review is a contemporary of some of Gould's articles on the same note: that paleontology was undergoing an exciting new time and scientific rigor was being re-injected into the discipline.
Woodroff goes on to describe Stanley's contributions to biology, and the wealth of analyses Stanley includes within the volume, including "well-illustrated data on rates of speciation, extinction, and the diversification of higher taxonomic categories." He goes through the average duration of the various species in various groups, and the various speeds at which diversification occurs. The problem of the varying speed by which species diversification appears in the fossil record is addressed as:
"This inconsistency has created a major problem for evolutionary biologists. Darwin and most subsequent authors including G.G. Simpson have held that most evolutionary transitions occur within established lineages by phyletic gradualism guided by natural selection. But fossil species remain unchanged throughout most of their history and the record fails to contain a single example of a significant transition. Similarly, it is difficult to account for the greatly accelerated pace of evolution during periods of adaptive radiation. An alternative model of evolution, introduced by Niles Eldredge and Stephan Jay Gould in the early 1970's, more fully accounts for these same observations. According to this major conceptual breakthrough, rapid evolution is typically associated with speciation events that occur cryptically in small isolated populations, often at the edge of a species's geographic range." (Woodroff, D.S., Science (208) 1980 716-717).
Clearly the authors intended the reader to note the weakness in gradualism, not to doubt the fact that the fossil record supports evolutionary theory, as the little quote nugget at the top of this record seems to imply.
"We have long known about stasis and abrupt appearance, but have chosen to fob it off upon an imperfect fossil record." (Gould, Stephen J., "The Paradox of the First Tier: An Agenda for Paleobiology," Paleobiology , 1985, p. 7)
This is a truly disgusting misquote that goes so far to allow me to call it, against my usual cautionary nature, "a creationist lie". It is implying sloppy scientific methods when the true quote has only a superficial resemblance to the word and none to the meaning.
It is a complete fabrication of the original sentence by the source which was:
"Just as we have long known about stasis and abrupt appearance, but have chosen to fob it off up on an imperfect fossil record, so too have we long recognized the rapid, if not sudden, turnover of faunas in episodes of mass extinction."
I truly enjoyed reading the article cited here, too, and it's worthy of a few discussions on its entire merit. But as I am obliged to give the full context of the "quote nugget", knowing it's my scholarly duty, let's go to it.
We must first start with the abstract. Gould presents the basics of his argument within the article's abstract, which is very important to read in this context. Here is quoted the entire abstract on page 2:
"Nature's discontinuities occur both in the hierarchical structuring of genological individuals and in the distinct processes operating at different scales of time, here called tiers. Conventional evolutionary theory denies this structuring and attempts to render the larger scales at simple extrapolation from (or reduction to) the familiar and immediate -- the struggle among organisms at ecological moments (conventional individuals at the first tier). I propose that we consider distinct processes at three separable tiers of time: ecological moments, normal genological time (trends during millions of years) and periodic mass extinctions.
"I designate as "the paradox of the first tier" our failure to find progress in life's history, when conventional theory (first tier processes acting on organisms) expects it as a consequence of competition under Darwin's metaphor of the wedge. I suggest a resolution of the paradox: whatever accumulates at the first tier is sufficiently reversed, undone, or overridden by processes of the higher tiers. In particular, punctuated equilibrium at the second tier produces trends for suites of reasons unrelated to the adaptive benefits of organisms (conventional progress). Mass extinction at the third tier, a recurring process now recognized as a more frequent, more rapid, more intense and more different than we had imagined, works by different rules and may undo whatever the lower tiers had accumulated." (Gould, Stephen J., "The Paradox of the First Tier: An Agenda for Paleobiology," Paleobiology 11(1) 1985, pp 2-12)
Now, to set the context of the "quote nugget" cited at the top of this section, it is in the light of the discussion on the "third tier". Note how Gould is criticizing other aspects of his field in its conclusions and methods, a habit that is typical of most critically-thinking scientists and is a necessary and prevalent method of discourse in science. Context given below.
"IV. Establishment of the Independence of the Third Tier.
As ideas whose time may have come, mass extinction shares an interesting property with punctuated equilibrium. Neither represents a new discovery both involve the reluctant acceptance of an acknowledged literal pattern that deep biases of Western thought had led us to mitigate or deny. Just as we have long known about stasis and abrupt appearance, but have chose to fob it off upon an imperfect fossil record, so too have we long recognized the rapid, if not sudden, turnover of faunas in episodes of mass extinction. We have based our geological alphabet, the time scale, upon these faunal replacements. Yet we have chosen to blunt or mitigate the rapidity and extent of extinctions with two habits of argument rooted in uniformitarian commitments. First, we have deemphasized some extinctions by drawing dubious phyletic connections across the boundaries. Second, and more important, we have tried to distribute these events more evenly in time by seeking evidence for slow declines before boundaries and reduced peaks of extinction at the terminations themselves. In short, we have tried to place mass extinctions into continuity with the rest of life's history by viewing them as only quantitatively different -- more and quicker of the same -- rather than qualitatively distinct in both rate and effect."
In other words, Gould is arguing for the need to treat mass extinctions as separate phenomena in themselves.
I would also like to add that in the previous section within this same paper, on the subject of the "Second Tier", Gould was making the case for the mechanism of punctuated equilibrium, where he showed that gradualism does not explain the stasis and abrupt appearance in the fossil record, which is in context with the work itself. Again, this section's particular misquote takes advantage of the discussion of the merits of [punctuated equilibrium] over gradualism. The misquoted phrase is reminding the reader that before the hypothesis of punctuated equilibrium was proposed in the early 70's, evolution was thought to operate as gradualism and the discontinuous fossil record was, as Gould said, excused as merely incomplete.
What makes this particular misquote even more egregious is that they didn't just take Gould out of context, but they engineered what he said in the first place. This misquote supports the creationist claims of scientific uber-conspiracies in favor of evolution, as if scientists deliberately ignore the fossil evidence and pass it off without debating it, which is hardly the case. Science demands that evidence be examined, critiqued, and debated, and this is what Gould is doing in this very paper, with the presentation of his case on the subject of hierarchical arrangements of mass extinctions in relation to other evolutionary changes!
What does Gould's good criticism and scholarship have to do with the implied-sloppy-scientific-method-mangled quote nugget above?
"Paleontologists ever since Darwin have been searching (largely in vain) for the sequences of insensibly graded series of fossils that would stand as examples of the sort of wholesale transformation of species that Darwin envisioned as the natural product of the evolutionary process. Few saw any reason to demur - though it is a startling fact that . most species remain recognizably themselves, virtually unchanged throughout their occurrence in geological sediments of various ages." (Eldredge, Niles, "Progress in Evolution?" New Scientist , vol. 110, 1986, p. 55)
At least this one gives a volume number. It is from the issue of 5 June 1986 (volume 110, number 1511), pages 54-57.
" -- though it is a startling fact that, of the half dozen reviews of the On the Origins of Species written by paleontologists that I have seen, all take Darwin to task for failing to recognize that most species remain recognizably themselves, virtually unchanged throughout their occurrence in geological sediments of various ages."
The sub-heading of this article (presumably written by the editor?) summarizes the article as:
"Darwin was right to regard natural selection as the only rational explanation for the design we see in nature. But he was wrong to abandon the notion of species as real entities."
As is the case with most, if not all, of the quotes taken from Stephen Jay Gould and Niles Eldredge, this passage involves their idea of Punctuated Equilibrium, which postulates that speciation occurs "quickly" (in geologic terms) in small isolated parts of the whole population. If that is true, we would expect examples of modification within species to be rare in the fossil record. Eldredge appears to be chiding paleontologists in the past for having noted, on the one hand, that the finely graded changes, that should have been evident if Darwin's was right that speciation occurred through slow change throughout the entire population, were missing, but failing, on the other hand, to challenge Darwin's idea of how speciation occurs. It is, again, an attempt to use a debate between scientists on a technical issue to unfairly portray the state of the evidence for evolution.
"In other words, when the assumed evolutionary processes did not match the pattern of fossils that they were supposed to have generated, the pattern was judged to be 'wrong.' A circular argument arises: interpret the fossil record in terms of a particular theory of evolution, inspect the interpretation, and note that it confirms the theory. Well, it would, wouldn't it? . As is now well known, most fossil species appear instantaneously in the record, persist for some millions of years virtually unchanged, only to disappear abruptly - the 'punctuated equilibrium' pattern of Eldredge and Gould." (Kemp, Tom S., "A Fresh Look at the Fossil Record," New Scientist , vol. 108, 1985, pp. 66-67)
In the paragraph this quote is taken from, Kemp is criticizing the claim that the fossil record is incomplete because it does not support gradualism. But the full quote is more illuminating:
The fact that the fossil data did not, on the whole, seem to fit this prevailing model of the process of evolution - for example, in the absence of intermediate forms and of gradually changing lineages over millions of years - was readily explained by the notorious incompleteness of the fossil record. In other words, when the assumed evolutionary processes did not match the pattern of fossils that they were supposed to have generated, the pattern was judged to be "wrong". A circular argument arises: interpret the fossil record in terms of a particular theory of evolution, inspect the interpretation, and note that it confirms the theory. Well, it would, wouldn't it?
Spearheaded by this extraordinary journal, palaeontology is now looking at what it actually finds, not what it is told that it is supposed to find. As is now well known, most fossil species appear instantaneously in the record, persist for some millions of years virtually unchanged, only to disappear abruptly - the "punctuated equilibrium" pattern of Eldredge and Gould. Irrespective of one's view of the biological causes of such a pattern (and there continues to be much debate about this), it leads in practice to description of long-term evolution, or macroevolution, in terms of the differential survival, extinction and proliferation of species. The species is the unit of evolution.
Note that Kemp states that the fossil record "leads in practice to description of long-term evolution. "
[Editor's note: In addition to being used to claim that "Sudden Appearance and Stasis" in the fossil record is an artifact of special creation, this quote mine is also used to "support" claims that geology has to assume evolution in order to derive dates from the fossil sequence, while the sequence is used as evidence of evolution, resulting in faulty circular reasoning.]
Notice that this particular quote mine is frequently grouped together with another:
And this poses something of a problem: If we date the rocks by their fossils, how can we then turn around and talk about patterns of evolutionary change through time in the fossil record?" - Niles Eldredge in Time Frames: The Rethinking of Darwinian Evolution and the Theory of Punctuated Equilibria , pp. 51, 52, (New York: Simon and Schuster, 1985)
By taking these out of context, it is made to superficially appear that they support the creationist claims of circuity of reasoning in that fossils date rocks which date fossils which date rock, etc. Henry Morris in "The Vanishing Case for Evolution" ( Impact 156) explicitly claims that this quote is about such circular reasoning. Under the heading "No Order in the Fossils," Morris claims:
Not only are there no true transitional forms in the fossils there is not even any general evidence of evolutionary progression in the actual fossil sequences (two quotes omitted). The superficial appearance of an evolutionary pattern in the fossil record has actually been imposed on it by the fact that the rocks containing the fossils have themselves been "dated" by their fossils.
That is followed by the two above quotes. The quote from Eldredge is not about dating and is flagrantly out of context (See Quote #3.6). The quote by Kemp is also out of context and, what is worse, it is not even about dating of fossils or geologic strata. The issue of the age of either the fossils or the rocks which contain them is not in any way addressed in this short article from the "Forum" section of the magazine.
What is being discussed are issues of the tempo and mode of evolution: how evolution proceeds and at what pace, not when the fossilized organisms lived. In other words this is really a punctuated equilibria quote. It is not unusual for those advocating new paradigms to think of themselves as the ones who finally bothered to pay attention to the evidence. Dr. Kemp is a supporter of punctuated equilibria which in 1985 was still a relatively new paradigm for paleontology.
The journal Paleobiology is 10 years old, and has celebrated the anniversary with a special number (vol. 11, no 1) devoted to a collection of invited reviews of the leading topics in paleobiological research. As the editors say, justifiably if a trifle immodestly, "the wealth and quality of innovative and provocative scientific papers that have appeared in Paleobiology over the past 10 years have provided a de facto definition for both its subject area and its mission.
And what exactly is that mission? Briefly, it seems to me, to propagate the view the fossils provide information about evolution that can be used to generate and test theory. That statement may appear obvious: after all, it is roughly what all sciences are supposed to do, and palaeontology has always been accepted as a science. But it actually represents something of a conceptual revolution in the subject.
Before the early 1970s, most paleontologists interpreted their fossil record in the light of the prevailing view of how evolution works, the NeoDarwinian, or synthetic theory. Thus, they attributed differences in the fossils found at different points in geologic time to natural selection acting on individual organism, causing a gradual evolutionary change in a more or less continuous fashion. Species became extinct, they said, because of competition from other, better adopted species. Even whole taxonomic groups competed with one another, to the advantage of some and the demise of others. New species arose by gradual transformation of a species, largely in response to environmental changes. Even mass extinctions resulted from a simple loss of fitness following a change in the environment.
And so on. He also explicitly discusses the "'punctuated equilibrium' pattern of Eldredge and Gould." Dr. Kemp is concerned that those who dig fossils use those fossils to discover what really happened and not impose on those fossils what theorists expect of those fossils. And he sees the journal Paleobiology as a place for scientists to tell what the fossils say.
. . . But the observed pattern of the fossils, as evidence of what really happened, must be as necessary a part of testing hypotheses about the evolutionary process as any amount of genetic and ecological knowledge about living organisms.
"The old Darwinian view of evolution as a ladder of more and more efficient forms leading up to the present is not borne out by the evidence. Most changes are random rather than systematic modifications, until species drop out. There is no sign of directed order here. Trends do occur in many lines, but they are not the rule." (Newell, N. D., "Systematics and Evolution," 1984, p. 10)
Let it be noted that almost everybody says this is true. But Darwinism never did require "more and more efficient forms", right from the get-go. That was Lamarck's theory.
"Well-represented species are usually stable throughout their temporal range, or alter so little and in such superficial ways (usually in size alone), that an extrapolation of observed change into longer periods of geological time could not possibly yield the extensive modifications that mark general pathways of evolution in larger groups. Most of the time, when the evidence is best, nothing much happens to most species." (Gould Stephen J., "Ten Thousand Acts of Kindness," Natural History , 1988, p. 14)
"Many people think that fossils, almost by definition, are rare and precious. (Some are, of course . . .) . . . But most ordinary fossils . . . are . . . abundant parts of their geological strata. . . The fossils are beautiful, and they are tempting. But they are also plentiful. . . .
Then the quote with the unmarked deletion restored and the following paragraph in its entirely:
"This extraordinary abundance of some fossils illustrates something important about the history of life. Evolution is a theory about change through time -- "descent with modification," in Darwin's words. Yet when fossils are most abundant during substantial stretches of time, well-represented species are usually stable throughout their temporal range or alter so little and in such superficial ways (usually in size alone) that an extrapolation of observed change into longer periods of geological time could not possibly yield the extensive modifications that mark general pathways of evolution in larger groups. Most of the time, when the evidence is best, nothing much happens to most species.
Niles Eldredge and I have tried to resolve this paradox with our theory of punctuated equilibrium. We hold that most evolution is concentrated in events of speciation, the separation and splitting off of an isolated population from a persisting ancestral stock. These events of splitting are glacially slow when measured on the scale of a human life -- usually thousands of years. But slow in our terms can be instantaneous in geological perspective. A thousand years is one-tenth of one percent of a million years, and a million years is a good deal less than average for the duration of most fossil species. Thus, if species tend to arise in a few thousand years and then persist unchanged for more than a million, we will rarely find evidence for their momentary origin, and our fossil record will tap only the long periods of prosperity and stability. Since fossil deposits of overwhelming abundance record such periods of success for widespread species living in stasis, we can resolve the apparent paradox that when fossils are most common, evolution is most rarely observed."
(See Gould, Stephen Jay 1993. "Ten Thousand Acts of Kindness," in Eight Little Piggies, Reflections in Natural History . New York: W.W.Norton & Company, pp. 275 - 278.)
Even if the quote-miner disagrees with Gould's and Eldredge's explanation for the state of the fossil record, to edit what they wrote to make it appear that they have no explanation is deeply dishonest.
"Stasis, or nonchange, of most fossil species during their lengthy geological lifespans was tacitly acknowledged by all paleontologists, but almost never studied explicitly because prevailing theory treated stasis as uninteresting nonevidence for nonevolution. . The overwhelming prevalence of stasis became an embarrassing feature of the fossil record, best left ignored as a manifestation of nothing (that is, nonevolution). (Gould, Stephen J., "Cordelia's Dilemma," Natural History , 1993, p. 15)
First of all, a more accessible source for this quote is: Gould, Stephen J. 1995. "Cordelia's Dilemma", Dinosaur in a Haystack . New York: Harmony Books, p. 127-128.
Note that the above starts with the unmarked deletion of "Before Niles Eldredge and I proposed the theory of punctuated equilibrium in 1972, the . . .".
The very next paragraph is, in its entirely:
"But Eldredge and I proposed that stasis should be an expected and interesting norm (not an embarrassing failure to detect change), and that evolution should be concentrated in brief episodes of branching speciation. Under our theory, stasis became interesting and worthy of documentation -- as a norm disrupted by rare events of change. We took as the motto of punctuated equilibrium: "Stasis is data." (One might quibble about the grammar, but I think we won the conceptual battle.) Punctuated equilibrium is still a subject of lively debate, and some (or most) of its claims may end up on the ash heap of history, but I take pride in one success relevant to Cordelia's dilemma: our theory has brought stasis out of the conceptual closet. Twenty-five years ago, stasis was a non-subject -- a "nothing" under prevailing theory. No one would have published, or even proposed, an active study of lineages known not to change. Now such studies are routinely pursued and published, and a burgeoning literature has documented the character and extent of stasis in quantitative terms.
This is yet another example of creationists misconstruing a debate among scientists (once again, about Punctuated Equilibria) as something more. Quite simply, Gould is chiding scientists for a misinterpretation of the fossil record bearing on the tempo and mode of evolution, not the fact that it occurred. If they really had an argument that the peculiarity of the fossil record that Gould is describing is evidence against the fact of evolution, then they should make the argument openly, so it and its ramifications could be tested, instead of trying to hijack the words of real scientists. But blowing smoke is so much easier.
"Paleontologists just were not seeing the expected changes in their fossils as they pursued them up through the rock record. . That individual kinds of fossils remain recognizably the same throughout the length of their occurrence in the fossil record had been known to paleontologists long before Darwin published his Origin . Darwin himself, . prophesied that future generations of paleontologists would fill in these gaps by diligent search . One hundred and twenty years of paleontological research later, it has become abundantly clear that the fossil record will not confirm this part of Darwin's predictions. Nor is the problem a miserably poor record. The fossil record simply shows that this prediction is wrong. . The observation that species are amazingly conservative and static entities throughout long periods of time has all the qualities of the emperor's new clothes: everyone knew it but preferred to ignore it. Paleontologists, faced with a recalcitrant record obstinately refusing to yield Darwin's predicted pattern, simply looked the other way." (Eldredge, N. and Tattersall, I., The Myths of Human Evolution , 1982, p. 45-46)
In the passages quoted, Eldredge and Tattersall are discussing the merits of gradualism, something the quote miner has left out, as we can see:
The main impetus for expanding the view that species are discrete at any one point in time, to embrace their entire history, comes from the fossil record. Paleontologists just were not seeing the expected changes in their fossils as they pursued them up through the rock record. Instead, collections of nearly identical specimens, separated in some cases by 5 million years, suggested that the overwhelming majority of animal and plant species were tremendously conservative throughout their histories.
That individual kinds of fossils remain recognizably the same throughout the length of their occurrence in the fossil record had been known to paleontologists long before Darwin published his Origin . Darwin himself, troubled by the stubbornness of the fossil record in refusing to yield abundant examples of gradual change, devoted two chapters to the fossil record. To preserve his argument he was forced to assert that the fossil record was too incomplete, to full of gaps, to produce the expected patterns of change. He prophesied that future generations of paleontologists would fill in these gaps by diligent search and then his major thesis - that evolutionary change is gradual and progressive - would be vindicated. One hundred and twenty years of paleontological research later, it has become abundantly clear that the fossil record will not confirm this part of Darwin's predictions. Nor is the problem a miserably poor record. The fossil record simply shows that this prediction is wrong.
The observation that species are amazingly conservative and static entities throughout long periods of time has all the qualities of the emperor's new clothes: everyone knew it but preferred to ignore it. Paleontologists, faced with a recalcitrant record obstinately refusing to yield Darwin's predicted pattern, simply looked the other way. Rather than challenge well-entrenched evolutionary theory, paleontologists tacitly agreed with their zoological colleagues that the fossil record was too poor to do much beyond supporting, in a general sort of way, the basic thesis that life had evolved.
Darwin argued that even though different groups of species today might seem very different from each other, they were linked by common ancestry. His theory predicted the existence of species that would document that link. Just a year after the Origin of Species was published, Darwin was gratified to learn of the discovery of a bird called Archaeopteryx that did just that. While it had feathers and wings, it also had reptilian traits not seen in living birds, such as a long tail and claws on its "hands." It's too bad that Darwin was not around to read the news about transitional fossils discovered just in the past decade. Many have been just as spectacular as Archaeopteryx , if not more so.
, here as depicted by artist Carl Buell, represents a key transitional creature between marine- and land-dwelling animals. Photo credit: Courtesy Carl Buell
In 2004, for example, scientists digging in the Arctic unearthed the fossil bones of a fishy relative of all land vertebrates, including us, called Tiktaalik . This 375 million-year-old animal had limbs complete with elbows, wrists, and a flexible neck. But it still lived underwater, where it used its gills to breathe. [For more on Tiktaalik , see "The Zoo of You" (in Editors' Picks at left).]
Whales in particular intrigued Darwin, because they were clearly mammals on the inside yet were so fish-like on the outside. In 1994, paleontologists reported the first fossil of a whale with legs, as Darwin had predicted. And over the past decade, they've uncovered a number of new fossils that fill in many of the details in the transition that whales made from land to sea between 50 and 40 million years ago.
For example, in 2001, Philip Gingerich of the University of Michigan and his colleagues reported the first ankle bone of a whale. This bone is particularly important to tracing the origin of whales, because it had a distinctive shape seen only in one group of mammals: even-toed hoofed mammals known as artiodactyls. Studies on whale DNA also completed over the past decade have consistently pointed to artiodactyls—and hippos in particular—as the closest living relatives of whales on land.
Abrupt Appearance of Biological Forms in the Fossil Record
“The rapid development as far as we can judge of all the higher plants within recent geological times is an abominable mystery.” (Darwin, and Seward, More Letters of Charles Darwin, London, 1903, pp. 20-21.) “Although this abominable mystery is often cited today, and sometimes declared solved, few realize that the mystery is deeper today than it was for Darwin.” (Buggs, R.J.A., “The Deepening of Darwin’s Abominable Mystery,” Nature Ecology & Evolution, 2017, p. 169.)
[On the abrupt appearance of both cartilaginous and bony fish] “This divergence occurred in the Palaeozoic era, at least 423 million years ago (Ma), leaving a vast temporal and evolutionary gulf between modern lineages, with ample time for new innovations to overwrite primitive conditions. (Brazeau, M., Friedman, M., “The Origin and Early Phylogenetic History of Jawed Vertebrates,” Nature 520, 2015, pp. 490–497.)
“Since the time of Darwin it has been known that fossils of animal life seem to appear suddenly in the fossil record.” (Ward, Peter D., Out of Thin Air, 2006, p. 51.)
“Blind acceptance of the fossil record can lead to erroneous conclusions, but ignoring it can be more serious. The fossil evidence indirectly but overwhelming supports the hypothesis that birds suffered a late Cretaceous demise, with a probable bottleneck of a few morphological forms (possibly paleognaths and ‘transitional shorebirds’) that produced a reorganization, diversification and explosive Tertiary radiation…” (Feduccia, Alan, “‘Big Bang’ for Tertiary Birds?,” TRENDS in Ecology and Evolution 18:4, April 2003, p. 174.)
“The earliest turtles had teeth and a reduced shell, but were otherwise similar to those of today.” (Hickman, et. al., Integrated Principles of Zoology, 2014, p. 561.) “The early evolution of turtles continues to be a contentious issue in vertebrate paleontology.” (Li, C., Fraser, N.C., Rieppel, O., and Wu, X.C., A Triassic Stem Turtle with an Edentulous Beak, Nature 560:476, 2018.) “[S]cientists who study the evolution of these animals have a running joke: turtles might as well have come from space.” (Black, R., “How the Turtle Got its Shell: Evolutionary Puzzle Finally Cracked,” New Scientist, May 2–8 2020, pp. 37.)
“Major transitions in biological evolution show the same pattern of sudden emergence of diverse forms at a new level of complexity. The relationships between major groups within an emergent new class of biological entities are hard to decipher and do not seem to fit the tree pattern that, following Darwin’s original proposal, remains the dominant description of biological evolution. The cases in point include the origin of complex RNA molecules and protein folds major groups of viruses archaea and bacteria, and the principal lineages within each of these prokaryotic domains eukaryotic supergroups and animal phyla. In each of these pivotal nexuses in life’s history, the principal “types” seem to appear rapidly and fully equipped with the signature features of the respective new level of biological organization. No intermediate “grades” or intermediate forms between different types are detectable. Usually, this pattern is attributed to cladogenesis compressed in time, combined with the inevitable erosion of the phylogenetic signal. … There seems to be a striking commonality between all major transitions in the evolution of life. In each new class of biological objects, the principal types emerge abruptly, and intermediate grades (e.g., intermediates between the precellular stage of evolution and prokaryotic cells or between prokaryotic and eukaryotic cells), typically, cannot be identified.” (Koonin, Eugene, “The Biological Big Bang model for the major transitions in evolution,” Biology Direct, 2007, 2:21.)
“Darwin used the only illustration in the first edition of The Origin of Species to explain his hypothesis that the patterns of evolution over hundreds of millions of generations were the same as those at the level of populations and species. In fact, they are clearly distinct in all taxonomic groups. Evolution at the level of populations and species might, in some cases, appear as nearly continuous change accompanied by divergence to occupy much of the available morphospace. However, this is certainly not true for long-term, large-scale evolution, such as that of the metazoan phyla, which include most of the taxa that formed the basis for the evolutionary synthesis. The most striking features of large-scale evolution are the extremely rapid divergence of lineages near the time of their origin, followed by long periods in which basic body plans and ways of life are retained. What is missing are the many intermediate forms hypothesized by Darwin, and the continual divergence of major lineages into the morphospace between distinct adaptive types. The most conspicuous event in metazoan evolution was the dramatic origin of major new structures and body plans documented by the Cambrian explosion. Until 530 million years ago, multicellular animals consisted primarily of simple, soft-bodied forms, most of which have been identified from the fossil record as cnidarians and sponges. Then, within less then 10 million years, almost all of the advanced phyla appeared, including echinoderms, chordates, annelids, brachiopods, molluscs and a host of arthropods. The extreme speed of anatomical change and adaptive radiation during this brief time period requires explanations that go beyond those proposed for the evolution of species within the modern biota.” (Carroll, Robert L. “Towards a New Evolutionary Synthesis,” Trends in Ecology & Evolution 15, 2000, pp. 27-32.)
“No wonder paleontologists shied away from evolution for so long. It seems never to happen. Assiduous collecting up cliff faces yields zigzags, minor oscillations, and the very occasional slight accumulation of changeover millions of years, at a rate too slow to really account for all the prodigious change that has occurred in evolutionary history. When we do see the introduction of evolutionary novelty, it usually shows up with a bang, and often with no firm evidence that the organisms did not evolve elsewhere! Evolution cannot forever be going on someplace else. Yet that’s how the fossil record has struck many a forlorn paleontologist looking to learn something about evolution.” (Eldredge, Niles, Reinventing Darwin: The Great Evolutionary Debate, 1996, p.95.)
“We are still in the dark about the origin of most major groups of organisms. They appear in the fossil record as Athena did from the head of Zeus—full blown and raring to go, in contradiction to Darwin’s depiction of evolution as resulting from the gradual accumulation of countless infinitesimally minute variations.” (Schwartz, Jeffrey H., Sudden Origins, 1999, p. 3.)
“For use in understanding the evolution of vertebrate flight, the early record of pterosaurs and bats is disappointing: Their most primitive representatives are fully transformed as capable fliers.” (Sereno, Paul C., “The Evolution of Dinosaurs, Science 284(5423), June 25, 1999, p. 2143.)
“Each species of mammal-like reptile that has been found appears suddenly in the fossil record and is not preceded by the species that is directly ancestral to it. It disappears some time later, equally abruptly, without leaving a directly descended species although we usually find that it has been replaced by some new, related species.” (Kemp, Tom, “The Reptiles that Became Mammals,” New Scientist, Vol. 92, 1982, p.583.)
“At the core of punctuated equilibria lies an empirical observation: once evolved, species tend to remain remarkably stable, recognizable entities for millions of years. The observation is by no means new, nearly every paleontologist who reviewed Darwin’s Origin of Species pointed to his evasion of this salient feature of the fossil record. But stasis was conveniently dropped as a feature of life’s history to he reckoned with in evolutionary biology.” (Eldredge, Niles, Time Frames: The Rethinking of Darwinian Evolution and the Theory of Punctuated Equilibria, 1985, p.188.)
“It is, indeed, a very curious state of affairs, I think, that paleontologists have been insisting that their record is consistent with slow, steady, gradual evolution where I think that privately, they’ve known for over a hundred years that such is not the case. …It’s the only reason why they can correlate rocks with their fossils, for instance. …They’ve ignored the question completely.” (Eldredge, Niles, “Did Darwin Get It Wrong?” Nova (November 1, 1981), 22 p. 6.)
“The record certainly did not reveal gradual transformations of structure in the course of time. On the contrary, it showed that species generally remained constant throughout their history and were replaced quite suddenly by significantly different forms. New types or classes seemed to appear fully formed, with no sign of an evolutionary trend by which they could have emerged from an earlier type.” (Bowler, Evolution: The History of an Idea, 1984, p. 187.)
Anti-creationist Arthur Strahler of Columbia University wrote, “This is one count in the creationists’ charge that can only evoke in unison from paleontologists a plea of nolo contendere [no contest].” (Arthur N. Strahler, Science and Earth History: The Evolution/Creation Controversy, 1987, pp. 408-409.)
“Paleontologists have paid an enormous price for Darwin’s argument. We fancy ourselves as the only true students of life’s history, yet to preserve our favored account of evolution by natural selection we view our data as so bad that we almost never see the very process we profess to study. …The history of most fossil species includes two features particularly inconsistent with gradualism: 1. Stasis. Most species exhibit no directional change during their tenure on earth. They appear in the fossil record looking much the same as when they disappear morphological change is usually limited and directionless. 2. Sudden appearance. In any local area, a species does not arise gradually by the steady transformation of its ancestors it appears all at once and ‘fully formed.’” (Gould, Stephen J. The Panda’s Thumb, 1980, p. 181-182.)
“Paleontologists are traditionally famous (or infamous) for reconstructing whole animals from the debris of death. Mostly they cheat. …If any event in life’s history resembles man’s creation myths, it is this sudden diversification of marine life when multicellular organisms took over as the dominant actors in ecology and evolution. Baffling (and embarrassing) to Darwin, this event still dazzles us and stands as a major biological revolution on a par with the invention of self-replication and the origin of the eukaryotic cell. The animal phyla emerged out of the Precambrian mists with most of the attributes of their modern descendants.” (Bengtson, Stefan, “The Solution to a Jigsaw Puzzle,” Nature, vol. 345 (June 28, 1990), pp. 765-766.)
“Beginning at the base of the Cambrian period and extending for about 10 million years, all the major groups of skeletonized invertebrates made their first appearance in the most spectacular rise in diversity ever recorded on our planet.” (Salvador E. Luria, Stephen Jay Gould, Sam Singer, A View of Life, 1981, p.649.)
“And it has been the paleontologist my own breed who have been most responsible for letting ideas dominate reality: …. We paleontologist have said that the history of life supports that interpretation [gradual adaptive change], all the while knowing that it does not.” (Niles Eldredge, Columbia Univ., American Museum Of Natural History, Time Frames, 1986, p.144.)
“Paleontologists had long been aware of a seeming contradiction between Darwin’s post ulate of gradualism…and the actual findings of paleontology. Following phyletic lines through time seemed to reveal only minimal gradual changes but no clear evidence for any change of a species into a different genus or for the gradual origin of an evolutionary novelty. Anything truly novel always seemed to appear quite abruptly in the fossil record.” (Mayr, E. One Long Argument: Charles Darwin and the Genesis of Modern Evolutionary Thought, 1991, p. 138.)
“Stepping way back and looking at too broad a scale, one might discern some sort of progress in life’s history. …But the pattern dissolves upon close inspection. Most structural complexity entered in a grand burst at the Cambrian explosion, and the history of Phanerozoic life since then has largely been a tale of endless variation upon a set Bauplane. We may discern a few ‘vectors’ of directional change – thickening and ornamentation of shells…–but these are scarcely the stuff of progress in its usual sense. …I believe our inability to find any clear vector of fitfully accumulating progress…represents our greatest dilemma for a study of pattern in life’s history.” (Gould, Stephen J., “The Paradox of the First Tier: an Agenda for Paleobiology,” Paleobiology, 1985, p. 3.)
“Perhaps we should not be surprised that vertebrate paleontologists did not support the prevailing view of slow, progressive evolution but tended to elaborate theories involving saltation, orthogenesis, or other vitalistic hypotheses. Most of the evidence provided by the fossil record does not support a strictly gradualistic interpretation, as pointed out by Eldridge and Gould…” (Carroll, Robert, Vertebrate Paleontology and Evolution, W. H. Freeman and Co., 1988, p 4.)
“The fossil record is much less incomplete than is generally accepted.” (Paul, C.R.C, “The Adequacy of the Fossil Record,” 1982, p. 75.)
“Enthusiastic paleontologists in several countries have claimed pieces of this missing record, but the claims have all been disputed and in any case do not provide real connections. That brings me to the second most surprising feature of the fossil record…the abruptness of some of the major changes in the history of life.” (Ager, D., The Nature of the Stratigraphical Record, 1981, p. 20.)
“The fossil record had caused Darwin more grief than joy. Nothing distressed him more than the Cambrian explosion, the coincident appearance of almost all complex organic designs…” (Gould, Stephen J., The Panda’s Thumb, 1980, p. 238-239.)
“Most families, orders, classes, and phyla appear rather suddenly in the fossil record, often without anatomically intermediate forms smoothly interlinking evolutionarily derived descendant taxa with their presumed ancestors.” (Eldredge, Niles, Macro-Evolutionary Dynamics: Species, Niches, and Adaptive Peaks, 1989, p. 22.)
“If evolution could produce ten new Cambrian phyla and then wipe them out just as quickly, then what about the surviving Cambrian groups? Why should they have had a long and honorable Pre-cambrian pedigree? Why should they not have originated just before the Cambrian, as the fossil record, read literally, seems to indicate, and as the fast-transition theory proposes? This argument, of course, is a death knell for the artifact theory.” (Gould, Stephen J., Wonderful Life: The Burgess Shale and the Nature of History, 1989, p. 273.)
“…one of the most striking and potentially embarrassing features of the fossil record. The majority of major groups appear suddenly in the rocks, with virtually no evidence of transition from their ancestors.” (Futuyma, D., Science on Trial: The Case for Evolution, 1983, p. 82.)
“Modern multicellular animals make their first uncontested appearance in the fossil record some 570 million years ago – and with a bang, not a protracted crescendo. This ‘Cambrian explosion’ marks the advent (at least into direct evidence) of virtually all major groups of modern animals – and all within the minuscule span, geologically speaking, of a few million years.” (Gould, Stephen J.,Wonderful Life: The Burgess Shale and the Nature of History, 1989, p. 23-24.)
“All through the fossil record, groups – both large and small – abruptly appear and disappear. …The earliest phase of rapid change usually is undiscovered, and must be inferred by comparison with its probable relatives.” (Newell, N. D., Creation and Evolution: Myth or Reality, 1984, p. 10.)
“The gaps in the record are real, however. The absence of any record of any important branching is quite phenomenal. Species are usually static, or nearly so, for long periods, species seldom and genera never show evolution into new species or genera but replacement or one by another, and change is more or less abrupt.” (Wesson, R., Beyond Natural Selection, 1991, p. 45.)
“The point emerges that if we examine the fossil record in detail, whether at the level of orders or of species, we find – over and over again – not gradual evolution, but the sudden explosion of one group at the expense of another.” (Ager, Derek V., “The Nature of the Fossil Record,” Proceedings of the British Geological Association, Vol. 87, 1976, p. 133.)
“A major problem in proving the theory has been the fossil record the imprints of vanished species preserved in the Earth’s geological formations. This record has never revealed traces of Darwin’s hypothetical intermediate variants – instead species appear and disappear abruptly, and this anomaly has fueled the creationist argument that each species was created by God.” (Czarnecki, Mark, “The Revival of the Creationist Crusade,” MacLean’s, January 19, 1981, p. 56.)
“No truly satisfactory explanation has yet been given for the origins of segmentation and the coelom, although the subject has stimulated much speculation and debate.” (Hickman, et. al., Integrated Principles of Zoology, 2011, p. 383.)
Are there any examples of sudden leaps in evolution? - Biology
Richard Dawkins, zoologist, highlights convergent evolution in the final chapter of his book, The Ancestor's Tale:
It seems that life, at least as we know it on this planet, is almost indecently eager to evolve eyes. We can confidently predict that a statistical sample of reruns [of evolutionary life on Earth] would culminate in eyes. And not just eyes, but compound eyes like those of an insect, a prawn, or a trilobite, and camera eyes like ours or a squid's, with color vision and mechanisms for fine-tuning the focus and the aperture. Also very probably parabolic reflector eyes like those of a limpet, and pinhole eyes like those of Nautilus, the latter-day ammonite-like mollusc in its floating coiled shell. And if there is life on other planets around the universe, it is a good bet that there will also be eyes, based on the same range of optical principles as we know on this planet. There are only so many ways to make an eye, and life as we know it may well have found them all. (page 588)
Like any zoologist, I can search my mental database of the animal kingdom and come up with an estimated answer to questions of the form: 'How many times has X evolved independently?' It would make a good research project, to do the counts more systematically. Presumably some Xs will come up with a 'many times' answer, as with eyes, or 'several times', as with echolocation. Others 'only once' or even 'never', although I have to say it is surprisingly difficult to find examples of these. And the difference could be interesting. I suspect that we'd find certain potential evolutionary pathways which life is 'eager' to go down. Other pathways have more 'resistance'. (page 590)
Please use this list in whatever ways you wish (and hotlink it to your own websites). And do let me know of other examples so that I can expand and improve what is offered here.
A 2009 headline in the British magazine New Scientist said “Darwin was wrong” and was immediately seized upon by creationists. Explain the issues and how the latest science is rewriting the idea of natural selection.
It’s not rewriting the idea of natural selection. Rather, it’s rewriting our understanding of evolution, of which natural selection is still a very important part. There are two phases in classic Darwinian evolution. First, there is the arising of variations from one creature to another or one individual population to another. That was thought to occur incrementally, in very slow stages, by mutations in the genome. Once there are variations among individuals, natural selection, the survival of the fittest, acts upon those variations.
What is new, and caused New Scientist to run that over-stated and provocative headline, “Darwin Was Wrong,” is that we now understand there is another, hugely significant form of variation. It’s not just incremental mutation, but horizontal gene transfer, bringing entirely new packages of DNA into genomes.
One of the axioms in Darwin’s day, natura non facit saltus, which your good Latin training [laughs] will tell you means nature does not make leaps things happen incrementally. But horizontal gene transfer has revealed that nature does sometimes make leaps, whereby huge lumps of DNA can appear in an individual or population quite suddenly and then natural selection acts on them. That can be a very important mechanism in the evolution of new species.
Can anyone expand upon the competing theories of evolution?
I know that there are slightly contrasting views of evolution within the scientific community. There's the classic Darwinian view of slow and steady evolution and the view that evolution must have, at least at times, occurred in leaps (often attributed to Stephen Jay Gould). Which way do most contemporary scientists lean? Why?
Edit: I understand that the ideas aren't "competing" and that evolution by natural selection isn't being contested. I'm just curious what the distinction between the two views/forms is and what's more common.
I think you're confusing things. Punctuated equilibrium is not a "competing theory" with evolution by natural selection.
Punctuated equilibrium is largely discredited these days. To be clear, this does not mean that evolution is never pulsed, that phenotypic evolution does not often occur at cladogenesis, or that rates of phenotypic evolution are not very different across the tree of life. These can all variously occur at different point in time, but punctuated equilibrium states that the occurrence of all of these processes together is the dominant mechanism of phenotypic evolution, which is not true.
This is a good review of why punctuated equilibrium is not a useful concept.
Edit: fixed link and some grammar
Trying to upvote you to the top. The point is that the "rate" of evolution is really determined by the strength of the selection pressure. Punctuated equilibrium is saying that evolution generally revolves around "strong" selection pressures, which doesn't make any sense considering the amount of diversity out there and considering the pervasive level of genetic drift.
I think the way to think about it isn't competing but more a problem of weighting different answers. To my knowledge, it seems like there is solid evidence for all the common ideas of evolution, the debate among scientists comes down to which forces were most important in a given situation. To oversimplify, was in 90% neutral drift and 10% strong selection, or 50/50, or 10/90, etc.
The reason these question are so hard is that it is really difficult to know precisely what pressures caused a particular thing to evolve. Sometimes we get really clear examples (like the Galapagos), where a species is physically isolated and evolution occurs in a truly divergent fashion. In, to my knowledge, most cases the lines are fuzzier and it is hard to pin down what caused a particular thing to evolve, especially at the gene regulatory level. I'm not an evolutionary biologist so others might know more details/can correct me, but from what I read in papers this seems to be the overall story.
Rapid, Dramatic 'Reverse Evolution' Documented In Tiny Fish Species
Evolution is supposed to inch forward over eons, but sometimes, at least in the case of a little fish called the threespine stickleback, the process can go in relative warp-speed reverse, according to a study led by researchers at Fred Hutchinson Cancer Research Center and published online ahead of print in the May 20 issue of Current Biology.
"There are not many documented examples of reverse evolution in nature," said senior author Catherine "Katie" Peichel, Ph.D., "but perhaps that's just because people haven't really looked."
Peichel and colleagues turned their gaze to the sticklebacks that live in Lake Washington, the largest of three major lakes in the Seattle area. Five decades ago, the lake was, quite literally, a cesspool, murky with an overgrowth of blue-green algae that thrived on the 20 million gallons of phosphorus-rich sewage pumped into its waters each day. Thanks to a $140 million cleanup effort in the mid-'60s -- at the time considered the most costly pollution-control effort in the nation -- today the lake and its waterfront are a pristine playground for boaters and billionaires.
It's precisely that cleanup effort that sparked the reverse evolution, Peichel and colleagues surmise. Back when the lake was polluted, the transparency of its water was low, affording a range of vision only about 30 inches deep. The tainted, mucky water provided the sticklebacks with an opaque blanket of security against predators such as cutthroat trout, and so the fish needed little bony armor to keep them from being eaten by the trout.
In 1968, after the cleanup was complete, the lake's transparency reached a depth of 10 feet. Today, the water's clarity approaches 25 feet. Lacking the cover of darkness they once enjoyed, over the past 40 years about half of Lake Washington sticklebacks have evolved to become fully armored, with bony plates protecting their bodies from head to tail. For example, in the late '60s, only 6 percent of sticklebacks in Lake Washington were completely plated. Today, 49 percent are fully plated and 35 percent are partially plated, with about half of their bodies shielded in bony armor. This rapid, dramatic adaptation is actually an example of evolution in reverse, because the normal evolutionary tendency for freshwater sticklebacks runs toward less armor plating, not more.
"We propose that the most likely cause of this reverse evolution in the sticklebacks is from the higher levels of trout predation after the sudden increase in water transparency," said Peichel, whose Hutchinson Center lab has established the stickleback as a new model for studying complex genetic traits. By examining multifaceted traits in the fish, such as body type and behavior, Peichel and colleagues shed light on the genetic networks at play in other complex traits, such as cancer and other common human diseases.
The ability of the fish to quickly adapt to environmental changes such as increased predation by the cutthroat trout is due, Peichel believes, to their rich genetic variation. The sticklebacks in Lake Washington contain DNA from both marine (saltwater) fish, which tend to be fully plated, and freshwater sticklebacks, which tend to be low-plated. When environmental pressures called for increased plating, some of the fish had copies of genes that controlled for both low and full plating, and so natural selection favored the latter.
"Having a lot of genetic variation in the population means that if the environment changes, there may be some gene variant that does better in that new environment than in the previous one, and so nature selects for it. Genetic variation increases the chance of overall survival of the species," she said.
The researchers' findings challenge a widely held theory behind rapid evolutionary change, the idea of "phenotypic plasticity" -- when an organism can take on different characteristics independent of genetic influences. Body type is one such example. "There is some genetic component to body size, but if you eat more nutritious food as a child you're probably going to grow taller than someone who has the same genes but may not have had as good of a diet growing up," Peichel said. "Our findings challenge the primary role of phenotypic plasticity in rapid evolutionary change."
The gene that controls for plating is called Eda, which comes in two forms: one causes low plating and the other complete plating. Peichel was the first person to home in on the neighborhood where the Eda gene lives while a postdoctoral researcher in the laboratory of David Kingsley, Ph.D., at Stanford University.
In humans, mutations in this gene cause a syndrome called ectodermal dysplasia, a group of more than 100 inherited disorders that impact the ectoderm, the outer layer of tissue involved in the formation of many parts of the body, including the skin, nails, hair, teeth and sweat glands.
"There's probably a developmental correlation between these external structures in humans and the bony plates on the fish," Peichel said. "It also looks like the Eda gene was probably important for human evolution although we don't really know in what context," she said.
Collaborators on the study included researchers from the University of Washington in Seattle the University of Texas in Austin Gifu Keizai University in Ogaki, Gifu, Japan and the Research Institute for Humanity and Nature in Kyoto, Japan. The work was supported by a Uehara Memorial Fellowship, the Packard Foundation, Seattle Public Utilities, Water and People Project, and a Burroughs Wellcome Fund Career Award in the Biomedical Sciences.
Protein-Protein Interactions in Human Disease, Part A
2.2 Some Evolutionary Aspects of Intrinsic Disorder and Protein Interactions
It was also pointed out that disordered proteins are characterized by wide diversification of evolutionary rates ( Brown, Johnson, Dunker, & Daughdrill, 2011 Brown et al., 2002 Khan, Douglas, Patel, Nguyen Ba, & Moses, 2015 Xue, Brown, Dunker, & Uversky, 2013 ), where some IDPs/IDPRs are highly conserved (e.g., α-synuclein, where sequences of human and fish (Larimichthys crocea) proteins share 63.5% identical residues, and where sequences of human and mouse proteins are different at only 7 out of 140 residues (have high identity of 95%)), whereas others possess high evolutionary rates. In fact, when amino acid sequences of proteins able to undergo folding on binding (FB) events were split on ordered regions, FB regions, disordered regions surrounding FB regions, and other disordered regions and subjected to evolutionary analysis, it was shown that ordered and FB regions are noticeably more conserved than disordered around FB regions, and other disordered regions ( Narasumani & Harrison, 2015 ). On the other hand, IDPs/IDPRs with high evolutionary rates can evolve into sophisticated and complex interaction centers (scaffolds) that can be easily tailored to the needs of divergent organisms (e.g., as it was described for emerin ( Yuan & Xue, 2015 ), C-terminal region of the viral polymerase protein A from the nodamura virus, NoV ( Gitlin, Hagai, LaBarbera, Solovey, & Andino, 2014 ), and an MDM2-interacting domain of p53 ( Borcherds, Kashtanov, Wu, & Daughdrill, 2013 )). It was also pointed out that the presence of conserved IDPRs within a single-domain protein may have a compensatory role, allowing such a protein to be multifunctional and possess various functions typically found in proteins with multiple domains ( Banerjee, Chakraborty, & De, 2017 ).