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Is greed an evolved trait?

Is greed an evolved trait?


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I am not a biologist, but I am fascinated by evolution.

I was watching the news this morning and, as so often is the case, there was a news story about a corrupt politician who was accepting bribes.

This started me thinking about how greed can become such a strong factor in one's life that it cancels out empathy for your fellow human beings.

So I was wondering--is greed an evolved trait? Maybe some result of an evolutionary pressure to hoard food for example?


The whole point about your question is to define what is an "evolved trait"? The concept of "evolved trait" does not exist in evolutionary biology. Here are various definitions I can think of that could apply to the expression "evolved traits".

Heritable Traits

Does evolved traits mean heritable traits?

A trait may be heritable or not. See for example my answer to this post to understand what heritable mean. You may want to understand the difference between the narrow and broad sense of heritability. Greed is probably heritable as several studies showed that many personality traits are heritable. This post will maybe give you more info.

--> Greed is probably a heritable trait

Traits that evolve

Does evolved traits mean traits that can evolve?

Any (existing) biological trait evolves. Not necessarily because they are selected for or against, neither even for genetic reasons, but traits change through times. Culture changes.

--> Yes, greediness can evolve

Traits that are adaptations

Does evolved traits mean traits that are adaptations?

The concept of adaptation is not always easy to define and its definition may vary from authors to authors. Simply speaking, an adaptation might be defined as a trait that is now fixed in the population (meaning that all individuals in the population carry this trait) but when it was not fixed yet it was beneficial. Such definitions would not fit the concept of greediness if we assume there is some genetic variance for greediness. But while I am not aware of any study on the subject, a level of greediness very probably influence the fitness (=~ reproductive success) of its carrier. If someone is extremely greedy, he might not find a mate and may fail to reproduce. On the other side, someone that is extremely generous may give everything it has up to its life and would definitely fail to reproduce. Therefore, it seems at first though that there is what we call stabilizing selection on the level of greediness.

--> It depends on the meaning of adaptation. But yes, it seems intuitive that greediness is a trait that undergoes (stabilizing) selection.


Social traits

Greediness is the kind of trait that are particularly interesting because it influences not only the fitness of its carrier but also the fitness of other individuals in the population. We say that it is a social trait and the field that study such traits is called social evolution. You'll need to get in touch with Hamilton's rule (Kin selection) and evolutionary game theory to understand more about the evolution of social traits. This post may eventually help you.


Wolverines Give Insight into the Evolution of Greed

Cross-posted with the permission of Dr. Nathan Lents from his The Human Evolution Blog.

Greed is often defined as the intense and selfish desire for something, especially wealth, power, or food. Although we usually associate this unseemly characteristic to humans, it is readily apparent that animals can also be greedy. Many animals are gluttonous, territorial, and many don’t seem at all interested in sharing. The reason is also obvious: the more you have, the better you’ll do when it comes to surviving and reproducing.

Greed, however, often takes things further than just acquiring resources for one’s self. It’s also about relative wealth. Humans don’t measure their own wealth in absolute terms, but rather in how their wealth stacks up to their neighbors. Why would this be? If the only matter at hand is one’s own health and reproduction, who cares what others do or have? Why would evolution have trained us to measure our wealth only in comparison to that of others?

Competition. Reproduction is always competitive, even in the best of times. No matter how many mates are freely available, some are more desirable than others. No matter how many offspring you can have, those offspring will have to vie for their place against other’s offspring.

Many animals, especially mammals, especially primates, and especially humans have evolved cooperative social structures and behaviors to augment the ruthless intraspecies competition seen in many other kinds of animals. But this does not mean that cooperation has totally replaced competition. Is is in our nature, as humans and as primates, to be both cooperative and competitive, depending on the conditions at the moment and the identity of the friend or foe in question.

For example, we are more likely to cooperate with kin than non-kin. In times of external threat, relatives will help each other and even fight and die for each other. However, within a family, there is plenty of competition as well. Sibling rivalry, anyone?

To answer this, let’s talk about the wolverine. This aggressive and powerful member of the weasel family has a reputation for being quite the bully. Wolverines can successfully fight off and chase away much larger animals including bears, cougars, and moose (!). There are even stories of a lone wolverine fending off an entire pack of wolves, each one of which probably outweighing the wolverine.

They also have a penchant for being smelly. Sometimes called the skunk bear, wolverines frequently spray their territory, their food, their mates, their offspring, and even themselves with a mist from their anal glands. Given their toughness, other animals are well advised to steer clear of the musky scent of the wolverine.

Not surprisingly, wolverines are expert hunters, rarely preyed upon, and comfortably at the top of their food web. Because their food sources are all in common with many other predators, they have become fierce competitors. Wolverines are known to chase other scavengers away from a carcass and they have no shame in stealing a hard earned kill from a smaller wolverine or even a different animal entirely.

They are voracious eaters, which gave rise to their various names in other languages such as “glutton” (in French), “gluttonous badger” (in Romanian), and “fat belly” (in Finnish). In fact, the scientific name of the wolverine is Gulo gulo, from the Latin word for gluttony.

Although wolverines sound rather like playground bullies, this is all pretty standard food competition. Where does the greed come in? Well, after a wolverine has eaten all it can whether from its own kill or find, or something it has stolen from some unfortunate shlemazl, it will actually spray the leftover food with its marking scent.

This might not seem so weird and biologists once thought that the wolverines were simply marking the food to protect its next meal of leftovers. However, this doesn’t seem to be the case. The wolverines rarely return to their leftovers. Sure, the distinctive wolverine scent alone is probably enough to dissuade many animals, but it turns out that the spray of wolverines, unlike that of skunks, is highly acidic. By spraying noxious carboxylic acids onto the leftover food, the wolverines actually accelerate the spoiling process.

To summarize, the wolverines have consumed all they can fit into their stomachs, and then they try to spoil any leftovers so that other predators and scavengers can’t eat them. This fits part of our description of greed. It’s not just about acquiring things it’s about having more than others have.

Those not comfortable assigning the term “greed” to these small weasels may counter that this is just a good competitive strategy. If an animal is in constant competition with other animals for the same food sources, there is an advantage in not feeding your competition. By leaving leftovers behind, the wolverines would be helping future competitors stay alive and live to fight another day.

My response to that is, “bingo!” Greed is precisely that! It is an intense competitive strategy that goes beyond just getting what you need. Greed is about seeing everything else as competition and measuring what you have against that of others.

These wolverines meet human definitions of greed because they take extra measures to harm the standing of competitors, or at least prevent them from being able to improve their own standing. No matter how much food may abound at that moment, wolverines consider every meal a zero-sum game. Out in the wild, there is no trophy for just participating and no silver medal for coming in second.

Wolverines know that wealth is relative, social standing is relative, and even access to food is relative. It’s great to be well-fed. It’s even better to be well-fed while others are starving.

Written by Prof. Nathan H. Lents

Professor Nathan H. Lents is a tenured associate professor of molecular biology at John Jay College of the City University of New York, a visiting professor at the University of Lincoln (UK), and author of "Not So Different: Finding Human Nature in Animals" (Columbia University Press, 2016). Professor Lents conducts research in three areas: forensic botany, the human microbiome, and teaching/learning biology at the college level. His work has been funded by the NIH, NSF, US Dept. of Ed, and the Susan G. Komen Breast Cancer Foundation. He also maintains The Human Evolution Blog and authors most of its content.

The views expressed above do not necessarily represent those of Visionlearning or our funding agencies.


Is Greed in the Genes?

Behavioral geneticists will tell you that intelligence and personality are highly heritable. But at least for economists, intelligence and personality are mainly interesting insofar as they predict that variable that “really” counts – income. How heritable is that?

Quite. This 2002 paper by Bowles and Gintis reports that identical twins’ incomes have a correlation of .56, versus .36 for fraternal twins. Using standard formulae, this implies that genes explains 40% of the variance of income, family environment 16%, and non-shared environment 44%. A recent working paper by David Cesarini gets income correlations of .545 for identicals versus .266 for fraternals, implying that genes explain 56% of the variance, shared environment -1%, and non-shared environment 45%.

It’s easy at this point to say, “Of course! Intelligence has a large effect on income and is highly heritable, so it follows that income will be highly heritable, too.” But Bowles and Gintis show that the heritability of income is far larger than the IQ effect can explain. (See Arnold’s doubts here).

What if you add in personality measures? David Cesarini does just this – and finds that measures of IQ and personality explain a bit more than one-third of the heritaibility of income. That’s a lot more than B&G got, but the glass is still two-thirds empty.

So where are the other two-thirds of the income heritability coming from? Here’s an hypothesis that seems promising to me:

1. Standard personality tests largely neglect the personality trait of greediness. (Alternate labels: Orientation toward money, materialism…)

2. Greediness is moderately-strongly heritable.

3. Greediness strongly predicts income, all else equal.

Take me, for instance. IQ tests say I’m smart, and personality tests say I’m conscientious. But money doesn’t matter much to me. When someone leaves academia to earn five times the income, I don’t feel envious I feel relieved not be to leaving academia! The end result: While I’m financially comfortable, I earn a lot less than many people with similar intelligence and work ethic.

So what do you think? If measured intelligence and conscientiousness account for one-third of the heritability of income, how much could measured greediness explain?

READER COMMENTS

Dennis Mangan
Mar 9 2009 at 2:27pm

I think it makes a lot of sense. In the book “The Millionaire Next Door”, the authors state that the millionaires they studied had one thing in common: a constant awareness of money, how to make it, and how to keep it. They looked at every decision in their lives as to how it would affect them financially. So they had a strong “orientation toward money”.

El Presidente
Mar 9 2009 at 3:21pm

I would guess about half, but that would be very hard to pin down. Would be fun to try though.

Mar 9 2009 at 3:29pm

Standard personality tests largely neglect the personality trait of greediness.

Wouldn’t this trait “greediness” be captured as a subset of one of the 5 standard personality types? I suppose it means isolating the effect of this particular trait, which supposedly nobody has done yet?

Barkley Rosser
Mar 9 2009 at 3:47pm

Face it. In a Galt-strike world, you are just a loser, :-).

Mar 9 2009 at 5:46pm

Not just greediness, but morally corruptible as well. I used to think Gapingvoid’s social hierarchy/corporate pyramid of losers, surmounted by the clueless, and topped by sociopaths was a joke, only to find it the reality.

Methinks
Mar 9 2009 at 5:57pm

I think how much money one makes is a poor measure of greed because it leaves out other forms of compensation.

Is someone who overuses a socialist healthcare system less greedy because his overuse can’t be calculated in his income? Is a person who abuses the welfare system to extract more goods and services without working for them less greedy than a person who invests his time and money to start a company just because the expected return on the start-up (along with the risk) is higher than the expected return on welfare fraud? Are the people voting for politicians to cut taxes for themselves while increasing taxes for another group less greedy than the entrepreneur?

I also don’t think your lack of envy is an indication that you’re less greedy. My mother also refuses to leave academia. Why would she? She has tons of time off, tenure (which means she no longer competes) and a pension coming from the university. Her life is set. That doesn’t mean she’s not greedy it just means she’s not motivated. I have my own business and I have none of her time off or security, but I’m compensated for that by making more money. If I weren’t, I might have settled for the cesspit of academia (sorry, I don’t know how you tolerate it).

Greed is just wanting more. Everyone is greedy. Everyone wants more of different things. Using income statistics to measure greed is just stupid. Who isn’t greedy for something?

Hamilton
Mar 9 2009 at 6:06pm

I like the points that Methinks makes. Isn’t your statement of “greediness” just a claim that you are very unwilling to trade a little time for thoughtful contemplation for even a great deal of material reward? And Methinks has the reverse of this situation? And, if so, aren’t we just saying that we can more precisely measure the one dimension (material reward) and not the other (time for contemplation)?

It’s not even that I disagree with you, I think. There probably is some personality trait that leads one to choose a life of questing for ever higher levels of material compensation over other forms of well being. I’m just not sure that “greediness” is the proper term for it.

Niccolo
Mar 9 2009 at 6:09pm

I think you make a mistake by factoring greed out of the equation of personality.

First, one has to ask, what is greed? Well, when analyzing greed and asking of its origins I come to a couple of conclusions about the person.

I think a greedy person is usually either,

A). Highly paranoid or uncertain about the future, thus amasses large amounts of wealth waiting in preparation for the inevitable storm.

B). Giving of him/herself to his/her loved ones, taking very little as an individual, but earning much to give to those in close proximity.

C). Possessing high tastes with feelings of inadequacies about anything but the best.

I think these three types of people are perfectly replicated in Jung’s personalities, so I don’t think there’s any need to separate greed from the equation of persona.

Dearieme
Mar 9 2009 at 7:05pm

A technical point: “have a correlation of .56, …Using standard formulae, this implies that genes explains 40% of the variance of income…”: I loathe that use of “explains”. Anyone who’s done an elementary stats course knows what you mean, of course, but it’s horribly misleading for the layman. First we tell him that correlation doesn’t imply cause, then we tell him that something that we infer from correlation “explains” something. Aargh!

But on your substantial point, I tend to agree that having a keen desire to make money probably does partly explain – in the layman’s sense – who makes money.

Lance
Mar 9 2009 at 7:07pm

I’ve always taken “The Fountainhead” for more than a metaphor and this article explains it

Zdeno
Mar 10 2009 at 12:26am

IIRC Bowles and Gintis also found a pretty significant coefficient on “locus of control” or something similar. Then of course there’s risk-taking, creativity, leadership etc. IQ tests are useful and informative, but there are a lot of traits it doesn’t capture that influence earning ability.

Greed is probably one of them, but I would prefer “materialism” or “consumption over leisure preference” since as someone pointed out, everyone is “greedy.”

Troy Camplin
Mar 10 2009 at 12:47am

Perhaps there is a certain amount of materialistic greed there, but I think other factors are at play. My experience has been that the poor are far more materialistic than the middle class or the wealthy. Many are poor because they waste whatever money they get on material goods rather than saving or investing the money to improve their economic situation.

I read somewhere recently that time horizons and one’s relation to time is highly predictive. Those with very short time horizons are poorer than those with very long time horizons. This does seem to have a genetic component to it. Further, the middle classes tend to be future-oriented, the poor present-oriented, and the wealthy past-oriented. How much of one’s relation to and perspective of time is heritable?

Stanfo
Mar 10 2009 at 1:09am

I continue to be amazed by how much you blog about topics and things that I have thought much about.

Bill shoe
Mar 10 2009 at 1:34am

I think “greedy” is a bit too simplistic. Greedy can be short or long term (Niccolo alludes to similar sub-types in previous comment). I think short term greed usually results in low income, long term greed results in high income. Long term greed also known as ability to delay gratification.

Standford Marshmallow Experiment demonstrated large correlation between delayed gratification ability and SAT performance. We know there is large correlation between SAT and IQ. Thus probably positive correlation between income and delayed gratification, with delayed gratification being similar but not identical to IQ. This has potential to explain income-IQ gap.

I think this is similar to Caplan’s theory, but with greed more narrowly defined and with delayed gratification ability being the smoking gun.

Mar 10 2009 at 8:21am

This 2002 paper by Bowles and Gintis reports that identical twins’ incomes have a correlation of .56, versus .36 for fraternal twins. Using standard formulae, this implies that genes explains 40% of the variance of income, family environment 16%, and non-shared environment 44%.

Please could anyone explain how you derive 40%, 16% and 44% from .56 and .36?

Fundamentalist
Mar 10 2009 at 9:18am

You really need to define greed. Do you really intend to suggest that the desire to improve one’s condition is greed?

“…identical twins’ incomes have a correlation of .56, versus .36 for fraternal twins. Using standard formulae, this implies that genes explains 40% of the variance of income…”

Maybe you meant the R-squared is .56, versus .36. The R-squared shows the explanatory power of the predictor variable, not the correlation. If the correlation is .56, then the R-square is 0.31 and genes explain 31% of the variance. If the correlation is .36, the R-squared is 0.13 and genes explain 13%. Also, this is a very simple model. I haven’t read the paper, but wonder if other variables were tested in order to determine if genetics was acting as a proxy for something else?

Mar 10 2009 at 2:29pm

It is known between geneticists how complex are even basic personality traits (its definition is other serious difficulty to a truthful scientific agenda), involving multiple genes and unknown interactions among them.

The “normality” has always been much more complex to typify (except in periods of authoritarian or aristocratic social framework). Pathological personality traits are easier characterized than non pathological attributes, however, even today there is not a consensus about the effects of child abuses (even moral abuses as excessive criticism) on the behavior in adult life (inclusive the development of social and academic skills), for example. A lot of case studies and some demographic figures show multiples long run aftereffects, despite of any genetical, social and economic attributes.

Sir Francis Galton (despite his important contributions to Statistics), his notions of Hereditary Genius and Eugenics need to be forgotten, but they are being retaken with a new name and package. Will it be necessary more millions of injured people to that ill-conceived ideas might be ignored?

Mar 10 2009 at 3:08pm

You’ve not considered the well known result that taller and more physically attractive people draw larger incomes.

Therefore the attention given to greed seems misplaced and biased.

LizWCU0966
Mar 10 2009 at 3:29pm

For decades scientists have argued the nature versus nurture argument concerning how much of that we become is a direct result of heredity and how much is a result of our environment. In Bryan Caplan’s blog he applies this argument to ones income and wealth, suggesting that greed is an inherited trait and greedy people will attain a higher level of income.
Personally I do not believe that ones ability to earn a higher income is passed down in their genes. I do believe that a person who grows up in a home with parents that are responsible and good role models will more than likely grow up to earn more money than someone who comes from a dysfunctional family whose caregivers don’t hold down steady jobs and spends their income on alcohol, drugs, or other devastating habits.
Someone growing up with a responsible parent is taught early on the importance of a job, of an education, of being fugal, of saving for the future and planning ahead. Maybe a person labeled as greedy only had the misfortune of growing up with greedy parents for role models. I myself believe that environment plays a larger role than heredity even when it comes to our personalities. Maybe Luther Burbank, a noted American botanist, summed it up best when he said “Heredity is nothing but stored environment.”

The Cupboard Is Bare
Mar 10 2009 at 5:49pm

It’s just my opinion, but greed has a negative connotation. When I think of greed, what comes to mind is a person who engages in unethical practices for personal gain of a financial or emotional nature.

Many people have a great deal of money and continue to make more, but I don’t consider them to be greedy unless that money was made in an unethical manner. Instead, I think of these people as being successful and fortunate enough to be doing something that makes them happy. Along the way, it’s not uncommon for them to help a lot of other people achieve both emotional and financial success.

I don’t know about the numbers, but what I have discovered is that parents who lie, cheat, steal, coerce and abuse in order to get what they want, frequently pass those traits on to their children. The children may say that they never want to be like their parents and for the most part avoid those behaviors but I have repeatedly seen examples where the child will exhibit the very behaviors they say they want to avoid when they want something badly enough.

Mr. Econotarian
Mar 10 2009 at 8:04pm

“Personally I do not believe that ones ability to earn a higher income is passed down in their genes.”

The truth holds regardless whether you “believe” it or not. The science shows that genes explain 56% of the variance of income.

Dearieme
Mar 10 2009 at 8:28pm

“Heredity is nothing but stored environment.”
You can live in a kennel but you won’t develop a wet snout and a waggly tail.

Mar 11 2009 at 1:28am

The behavioral geneticists would use better their time and skills forecasting the long term values to the equation x(n+1)=r*x(n)*(1-x(n)) with r in [3.6,4] and x(0) in (0,1).

Laurenwcu
Mar 18 2009 at 7:12pm

Professor Caplan asks an interesting question in his blog post. He asks, is greediness genetic? Caplan makes the astute observation that even though he himself is considered “smart” and “conscientious,” he does not feel the need to go after a job that would increase his income. This is a key difference in those who are greedy and those who really don’t care about money. Even though Caplan has the mental capacity to take on the job he chooses to make less money because he enjoys his job in academia.

With this said, I think that people, in general, have a drive to want something. This something can be material, money, cars, and houses, or something that rewards the mind, a challenge, happiness, and success. Often times one believes the material items in life will lead to happiness and create the illusion of success. I feel that this ideology is passed on from our parents to us. Most parents raise their children for success, and in today’s society success is shown through material possessions. As children grow they begin to form their own opinions that often times are similar to those their parents impose on them. This is why greediness appears to be genetic.

Involving the idea of the correlation of intelligence to greediness is a unique concept. Through my eyes, I see well-educated people being able to go beyond the idea that material possessions equals success. However, this sometimes is not the case. Many well-educated people are influenced by money to change jobs, even if it means not being happy. I think this happens because, they think money will give them happiness. Essentially, they are replacing the happiness that was in their old job for the happiness from money that they will experience in their new job. They are now forced to spend money on material possessions to try and get happy.

All in all, I think it would be nice to be able to drive an Audi A5 to work everyday, park it in my parking spot, slave over work, and then drive it home. But, the idea that I have a problem with is, is it going to make me happy. I cannot answer that question because I have never experienced this, but I can tell you that I am happy with my life and that is because the people who are in it. I also feel that my parents raised me to be this way to have success and happiness through life, not material possessions.


Is greed an evolved trait? - Biology

"Error. Greed does not compute."
May 2011

Where's the evolution?
What exactly is the conundrum regarding altruism? In evolutionary terms, altruistic behaviors are those that decrease the fitness of the individual performing the behavior (e.g., a meerkat that sounds the alarm about an approaching jackal, putting herself at a higher risk of attack) and increase the fitness of one or more other individuals (e.g., other meerkats in the colony that are able to escape the jackal attack). We've observed many examples of such selfless behavior across the natural world. The question for evolutionary biologists is, how do altruistic behaviors evolve to become common in populations? After all, natural selection decreases the frequency of gene versions that hinder their carrier's ability to survive and reproduce. Any meerkat that happens to have a gene that causes it to risk its own life for the life of its colony mates should be less likely to survive to reproduce and less likely to pass that altruistic gene on to the next generation. Based on this line of reasoning, natural selection should drive altruistic behaviors out of populations! So what's going on?

Biologists have considered many different hypotheses to explain the evolution of altruism. One of the most important is based on kinship. The basic idea is that if self-sacrificing behaviors help the altruist's relatives survive and reproduce, altruistic genes can spread in a population because they are likely to be passed on to future generations through the relatives, although not through the altruist him or herself. To understand this hypothesis, consider the case of the meerkats described above. Imagine that the meerkat sounding the warning (let's call her Flower) does so because she carries an "altruistic gene." What happens to the gene if Flower dies but saves the lives of several other individuals in her colony? Well, if Flower is the only one with the altruistic gene, it dies with her. However, if the individuals she saves are her relatives — e.g., her siblings, nieces, nephews, and children — odds are that many of them also carry the altruistic gene and will be able to pass it on to their offspring because of Flower's good deed. Altruism can spread in the meerkat population in this way. This is one example of kin selection — a form of natural selection that is caused by interactions among related individuals.

Some popular articles describe this hypothesis about the evolution of altruism as one animal helping a relative in order to pass on their shared genes however, this is a bit misleading. Natural selection has no foresight and does not require any intent on the part of the organism undergoing evolution. Organisms that display altruistic behaviors are not necessarily "trying" to pass on genes through their relatives they may be unaware of the effect of their actions or — for example, in the case of altruistic slime molds — may not have any sort of consciousness at all!

The hypothesis simply suggests that altruistic behaviors that happen to have the effect of promoting the fitness of relatives can spread — and specifically, that this is more likely to happen the more closely related the altruist and the recipient are, the less the altruist has to sacrifice to help the other, and the bigger the benefit the recipient gets. This makes intuitive sense. Closer relatives are likely to share more of their genes. So Flower's altruistic gene is more likely to spread if it ends up helping her sibling (who shares half of her DNA) than if it ends up helping her cousin (who shares just 1/8 of her DNA). Similarly, if Flower's altruistic behavior is very unlikely to get her killed, or is very likely to save the lives of her family, the altruistic gene is more likely to spread. The detailed form of this hypothesis (which gives numerical values to the relatedness of individuals and the benefit and cost of the altruistic act) is known as Hamilton's rule, after evolutionary biologist W.D. Hamilton who proposed the idea in 1964.

The robots in the recently published study were used to test Hamilton's rule. Each robot was controlled by a simple computer program (which you can think of as its DNA) with 33 different parts (i.e., with 33 "genes") that influenced different aspects of the robot's behavior — its movement, sensing ability, and how likely it is to share disks representing food with others (i.e., its altruism gene). Groups of robots were placed in arenas with food disks to collect. At the beginning of the experiment, each robot had random settings for its computer program. Some robots ran into walls, some stuttered in place, and some, just by chance, happened to move in a way that pushed a food disk. After allowing the robots to show their stuff, the researchers evaluated how well each robot did at obtaining food — a measure of evolutionary fitness. They formed a new generation of robots from the computer programs of the old generation (simulating recombination and reproduction), but with a twist: the better a robot was at obtaining food, the more likely it was that elements of its computer program would make it into the next generation. Each generation, the researchers also "mutated" the robot genomes, introducing small random changes into their computer programs. The researchers repeated this experiment over and over, simulating the robots' performance — and in each trial, over 500 generations of natural selection, the robots rapidly evolved efficient foraging abilities.

Robots rapidly evolve improved foraging abilities through natural selection. The different colored lines on the graph represent robot groups with different levels of relatedness and different degrees of costs and benefits for shared food disks.

In the most important part of their study, the researchers tested what would happen if the robots were more or less related to one another — i.e., if some of the robots in a group started off with computer programs that were genetically identical to one another. In these cases, the robots evolved exactly as we would expect them to based on Hamilton's rule. The more closely related the robot group was (i.e., the more clones it contained), the more likely the whole group was to evolve altruistic behavior and ultimately wind up sharing all their food disks. And the less an individual robot lost by sharing a food disc and the more other robots benefited from shared food discs, the more likely altruism was to evolve. Hamilton's rule did seem to hold in this simulation, which closely mimicked many aspects of a real, biological population.

The experimental set-up shown in this video is similar to the one used in this study. At the beginning of the experiment, robots are poor foragers. By the end, many groups have evolved altruistic foraging behaviors.

This result is important because, in nature, it would be very difficult to perform similar experiments and impossible to perform them over and over again. So, while many different lines of evidence support the idea of Hamilton's rule, this is the first time that biologists have been able to study it so exhaustively and with such accuracy — albeit in robots instead of actual living organisms. Nature is not always red in tooth and claw it is often generous, kind, and unselfish — and these results help us understand why such traits have evolved over and over again.

    Floreano, D., and Keller, L. (2010). Evolution of adaptive behaviour in robots by means of Darwinian selection. PLoS Biology. 8: e1000292.

from the Los Angeles Times

Understanding Evolution resources:

Discussion and extension questions

    What does it mean to say that individual A is more evolutionarily "fit" than individual B?

What is the key difference between the evolution of a trait like camouflaged coloration via natural selection and the evolution of a trait like altruism via kin selection? What are the similarities between these two processes?

    Which color represents populations in which you would expect Hamilton's rule to lead to the evolution of altruism?


Related lessons and teaching resources

    : In this classroom activity for grades 9-12, students build and modify paper-and-straw "birds" to simulate natural selection acting on random mutations.

: This news brief for grades 9-16, explains how the evolutionary implications of cheetah behavior may help conservation efforts targeting these endangered animals.


Homoplasy Examples

Homoplasy in Wings

The easiest homoplasy to understand is the trait of wings. Throughout the animal kingdom, wings have evolved in a number of various shapes and materials, but their fundamental function is the same: flight. Birds, bats, and many insects have evolved wings. In each case, the trait evolved independently of the other groups. The closest common ancestor of birds, bats and insects most certainly did not have wings. After the lineages diverged, or headed off in their own direction, a similar pressure of flight being advantageous caused all lineages to develop flight.

In each case, they also found their own way to develop wings. Bird wings are specially adapted forelimbs covered in feathers. The tarsals and metatarsals (hand and wrist bones) are formed in birds in such a way that they effectively have no fingers, but instead have an elongated limb that forms a strong leading edge for the wing. The feathers serve to give wing structure and, in this way, lift is generated, much like by the wings of an airplane.

Bats, like birds, also have modified wrist and finger bones. Unlike birds, bats do not have feathers, as this trait never evolved in bats. Because of this, bats support their wings with very long finger bones, or tarsals. Thus, in the same way as birds, bats create lift with their wings and are able to fly. Insects are another group of animals with the ability to fly, and their wings are even more complex.

Because of the complexity of the insect world, it is not certain whether insect wings are a homoplasy or a homology. Imagine butterfly wings. If you were to look up close, you would see that these enormous wings (compared to the insect) are covered in small scales, which make beautiful colors. The butterfly flaps them slowly and seems to glide through the air with ease. Compare these enormous, beautiful wings to those of a beetle. The beetle, to get his wings out, must open his hard outer covering and unfold or expand his much more fragile wings. They are thin, translucent (you can see through them), and they do not appear strong enough to be able to carry the beetle. Then, the beetle flaps them at an enormous rate and is quickly carried away by the lift they generate.

Homoplasy in Beaks

While not an often cited homoplasy, a squid and a falcon share a trait. At the opening of their mouth is a large beak, often sharp and meant to tear their prey apart. However, it can be seen immediately from their forms, locations of living, and closest genetic relatives, that the octopus and the falcon did not get their beaks from a common ancestor. The beaks evolved through convergence, or in other words, a similar need to rip throat-sized chunks from a prey animal. While it might not be pretty, evolution does tend to produce similar results given similar circumstances.

Not a Homoplasy

Now that you have a decent understanding of what a homoplasy is, let’s go over what it is not. Any time the trait is passed from parent to offspring, the trait is not a homoplasy. If a parent passes the trait to their offspring, the trait is a homology. When the trait gets passed down a long line of ancestors, the descendants can start to vary from each other in many ways. However, if they both still possess the trait, it is still a homologous trait, and not a homoplasy.

For instance, we are all familiar with mammals. Scientist, through years of study of their defining traits, and more recently, confirmations provided by genetic testing, have shown that mammals are a definable group of animals. These animals, by definition, have mammary glands which they use to feed their young. Although the mammary glands of whales and cows look different, and function in different ways, they are evolved from a common ancestor that had a primitive form of mammary glands. Therefore, mammary glands in whales and cows are homologous, not homoplastic.


Contents

E. O. Wilson defined sociobiology as "the extension of population biology and evolutionary theory to social organization". [3]

Sociobiology is based on the premise that some behaviors (social and individual) are at least partly inherited and can be affected by natural selection. [4] It begins with the idea that behaviors have evolved over time, similar to the way that physical traits are thought to have evolved. It predicts that animals will act in ways that have proven to be evolutionarily successful over time. This can, among other things, result in the formation of complex social processes conducive to evolutionary fitness.

The discipline seeks to explain behavior as a product of natural selection. Behavior is therefore seen as an effort to preserve one's genes in the population. Inherent in sociobiological reasoning is the idea that certain genes or gene combinations that influence particular behavioral traits can be inherited from generation to generation. [5]

For example, newly dominant male lions often kill cubs in the pride that they did not sire. This behavior is adaptive because killing the cubs eliminates competition for their own offspring and causes the nursing females to come into heat faster, thus allowing more of his genes to enter into the population. Sociobiologists would view this instinctual cub-killing behavior as being inherited through the genes of successfully reproducing male lions, whereas non-killing behavior may have died out as those lions were less successful in reproducing. [6]

The philosopher of biology Daniel Dennett suggested that the political philosopher Thomas Hobbes was the first sociobiologist, arguing that in his 1651 book Leviathan Hobbes had explained the origins of morals in human society from an amoral sociobiological perspective. [7]

The geneticist of animal behavior John Paul Scott coined the word sociobiology at a 1948 conference on genetics and social behaviour which called for a conjoint development of field and laboratory studies in animal behavior research. [8] [9] With John Paul Scott's organizational efforts, a "Section of Animal Behavior and Sociobiology" of the Ecological Society of America was created in 1956, which became a Division of Animal Behavior of the American Society of Zoology in 1958. In 1956, E. O. Wilson came in contact this emerging sociobiology through his PhD student Stuart A. Altmann, who had been in close relation with the participants to the 1948 conference. Altmann developed his own brand of sociobiology to study the social behavior of rhesus macaques, using statistics, and was hired as a "sociobiologist" at the Yerkes Regional Primate Research Center in 1965. [9] Wilson's sociobiology is different from John Paul Scott's or Altmann's, insofar as he drew on mathematical models of social behavior centered on the maximisation of the genetic fitness by W. D. Hamilton, Robert Trivers, John Maynard Smith, and George R. Price. The three sociobiologies by Scott, Altmann and Wilson have in common to place naturalist studies at the core of the research on animal social behavior and by drawing alliances with emerging research methodologies, at a time when "biology in the field" was threatened to be made old-fashioned by "modern" practices of science (laboratory studies, mathematical biology, molecular biology). [10] [9]

Once a specialist term, "sociobiology" became widely known in 1975 when Wilson published his book Sociobiology: The New Synthesis, which sparked an intense controversy. Since then "sociobiology" has largely been equated with Wilson's vision. The book pioneered and popularized the attempt to explain the evolutionary mechanics behind social behaviors such as altruism, aggression, and nurturance, primarily in ants (Wilson's own research specialty) and other Hymenoptera, but also in other animals. However, the influence of evolution on behavior has been of interest to biologists and philosophers since soon after the discovery of evolution itself. Peter Kropotkin's Mutual Aid: A Factor of Evolution, written in the early 1890s, is a popular example. The final chapter of the book is devoted to sociobiological explanations of human behavior, and Wilson later wrote a Pulitzer Prize winning book, On Human Nature, that addressed human behavior specifically. [9] [11]

Edward H. Hagen writes in The Handbook of Evolutionary Psychology that sociobiology is, despite the public controversy regarding the applications to humans, "one of the scientific triumphs of the twentieth century." "Sociobiology is now part of the core research and curriculum of virtually all biology departments, and it is a foundation of the work of almost all field biologists" Sociobiological research on nonhuman organisms has increased dramatically and continuously in the world's top scientific journals such as Nature and Science. The more general term behavioral ecology is commonly substituted for the term sociobiology in order to avoid the public controversy. [12]

Sociobiologists maintain that human behavior, as well as nonhuman animal behavior, can be partly explained as the outcome of natural selection. They contend that in order to fully understand behavior, it must be analyzed in terms of evolutionary considerations.

Natural selection is fundamental to evolutionary theory. Variants of hereditary traits which increase an organism's ability to survive and reproduce will be more greatly represented in subsequent generations, i.e., they will be "selected for". Thus, inherited behavioral mechanisms that allowed an organism a greater chance of surviving and/or reproducing in the past are more likely to survive in present organisms. That inherited adaptive behaviors are present in nonhuman animal species has been multiply demonstrated by biologists, and it has become a foundation of evolutionary biology. However, there is continued resistance by some researchers over the application of evolutionary models to humans, particularly from within the social sciences, where culture has long been assumed to be the predominant driver of behavior.

Sociobiology is based upon two fundamental premises:

  • Certain behavioral traits are inherited,
  • Inherited behavioral traits have been honed by natural selection. Therefore, these traits were probably "adaptive" in the environment in which the species evolved.

Sociobiology uses Nikolaas Tinbergen's four categories of questions and explanations of animal behavior. Two categories are at the species level two, at the individual level. The species-level categories (often called "ultimate explanations") are

  • the function (i.e., adaptation) that a behavior serves and
  • the evolutionary process (i.e., phylogeny) that resulted in this functionality.

The individual-level categories (often called "proximate explanations") are

Sociobiologists are interested in how behavior can be explained logically as a result of selective pressures in the history of a species. Thus, they are often interested in instinctive, or intuitive behavior, and in explaining the similarities, rather than the differences, between cultures. For example, mothers within many species of mammals – including humans – are very protective of their offspring. Sociobiologists reason that this protective behavior likely evolved over time because it helped the offspring of the individuals which had the characteristic to survive. This parental protection would increase in frequency in the population. The social behavior is believed to have evolved in a fashion similar to other types of nonbehavioral adaptations, such as a coat of fur, or the sense of smell.

Individual genetic advantage fails to explain certain social behaviors as a result of gene-centred selection. E.O. Wilson argued that evolution may also act upon groups. [13] The mechanisms responsible for group selection employ paradigms and population statistics borrowed from evolutionary game theory. Altruism is defined as "a concern for the welfare of others". If altruism is genetically determined, then altruistic individuals must reproduce their own altruistic genetic traits for altruism to survive, but when altruists lavish their resources on non-altruists at the expense of their own kind, the altruists tend to die out and the others tend to increase. An extreme example is a soldier losing his life trying to help a fellow soldier. This example raises the question of how altruistic genes can be passed on if this soldier dies without having any children. [14]

Within sociobiology, a social behavior is first explained as a sociobiological hypothesis by finding an evolutionarily stable strategy that matches the observed behavior. Stability of a strategy can be difficult to prove, but usually, it will predict gene frequencies. The hypothesis can be supported by establishing a correlation between the gene frequencies predicted by the strategy, and those expressed in a population.

Altruism between social insects and littermates has been explained in such a way. Altruistic behavior, behavior that increases the reproductive fitness of others at the apparent expense of the altruist, in some animals has been correlated to the degree of genome shared between altruistic individuals. A quantitative description of infanticide by male harem-mating animals when the alpha male is displaced as well as rodent female infanticide and fetal resorption are active areas of study. In general, females with more bearing opportunities may value offspring less, and may also arrange bearing opportunities to maximize the food and protection from mates.

An important concept in sociobiology is that temperament traits exist in an ecological balance. Just as an expansion of a sheep population might encourage the expansion of a wolf population, an expansion of altruistic traits within a gene pool may also encourage increasing numbers of individuals with dependent traits.

Studies of human behavior genetics have generally found behavioral traits such as creativity, extroversion, aggressiveness, and IQ have high heritability. The researchers who carry out those studies are careful to point out that heritability does not constrain the influence that environmental or cultural factors may have on those traits. [15] [16]

Criminality is actively under study, but extremely controversial. [ citation needed ] Various theorists have argued that in some environments criminal behavior might be adaptive. [17] The evolutionary neuroandrogenic (ENA) theory, by sociologist/criminologist Lee Ellis, posits that female sexual selection have led to increased competitive behavior among men, leading to criminality in some cases. In another theory, Mark van Vugt argues that a history of intergroup conflict for resources between men have led to differences in violence and aggression between men and women. [18] The novelist Elias Canetti also has noted applications of sociobiological theory to cultural practices such as slavery and autocracy. [19]

Genetic mouse mutants illustrate the power that genes exert on behaviour. For example, the transcription factor FEV (aka Pet1), through its role in maintaining the serotonergic system in the brain, is required for normal aggressive and anxiety-like behavior. [20] Thus, when FEV is genetically deleted from the mouse genome, male mice will instantly attack other males, whereas their wild-type counterparts take significantly longer to initiate violent behaviour. In addition, FEV has been shown to be required for correct maternal behaviour in mice, such that offspring of mothers without the FEV factor do not survive unless cross-fostered to other wild-type female mice. [21]

A genetic basis for instinctive behavioural traits among non-human species, such as in the above example, is commonly accepted among many biologists however, attempting to use a genetic basis to explain complex behaviours in human societies has remained extremely controversial. [22] [23]

Steven Pinker argues that critics have been overly swayed by politics and a fear of biological determinism, [a] accusing among others Stephen Jay Gould and Richard Lewontin of being "radical scientists", whose stance on human nature is influenced by politics rather than science, [25] while Lewontin, Steven Rose and Leon Kamin, who drew a distinction between the politics and history of an idea and its scientific validity, [26] argue that sociobiology fails on scientific grounds. Gould grouped sociobiology with eugenics, criticizing both in his book The Mismeasure of Man. [27]

Noam Chomsky has expressed views on sociobiology on several occasions. During a 1976 meeting of the Sociobiology Study Group, as reported by Ullica Segerstråle, Chomsky argued for the importance of a sociobiologically informed notion of human nature. [28] Chomsky argued that human beings are biological organisms and ought to be studied as such, with his criticism of the "blank slate" doctrine in the social sciences (which would inspire a great deal of Steven Pinker's and others' work in evolutionary psychology), in his 1975 Reflections on Language. [29] Chomsky further hinted at the possible reconciliation of his anarchist political views and sociobiology in a discussion of Peter Kropotkin's Mutual Aid: A Factor of Evolution, which focused more on altruism than aggression, suggesting that anarchist societies were feasible because of an innate human tendency to cooperate. [30]

Wilson has claimed that he had never meant to imply what ought to be, only what is the case. However, some critics have argued that the language of sociobiology readily slips from "is" to "ought", [26] an instance of the naturalistic fallacy. Pinker has argued that opposition to stances considered anti-social, such as ethnic nepotism, is based on moral assumptions, meaning that such opposition is not falsifiable by scientific advances. [31] The history of this debate, and others related to it, are covered in detail by Cronin (1993), Segerstråle (2000), and Alcock (2001).


Contents

The term paraphyly, or paraphyletic, derives from the two Ancient Greek words παρά ( pará ), meaning "beside, near", and φῦλον ( phûlon ), meaning "genus, species", [2] [3] and refers to the situation in which one or several monophyletic subgroups of organisms (e.g., genera, species) are left apart from all other descendants of a unique common ancestor.

Conversely, the term monophyly, or monophyletic, builds on the Ancient Greek prefix μόνος ( mónos ), meaning "alone, only, unique", [2] [3] and refers to the fact that a monophyletic group includes organisms consisting of all the descendants of a unique common ancestor.

By comparison, the term polyphyly, or polyphyletic, uses the Ancient Greek prefix πολύς ( polús ), meaning "many, a lot of", [2] [3] and refers to the fact that a polyphyletic group includes organisms arising from multiple ancestral sources.

In cladistics Edit

Groups that include all the descendants of a common ancestor are said to be monophyletic. A paraphyletic group is a monophyletic group from which one or more subsidiary clades (monophyletic groups) are excluded to form a separate group. Philosopher of science Marc Ereshefsky has argued that paraphyletic taxa are the result of anagenesis in the excluded group or groups. [4] Cladists do not grant paraphyletic assemblages the status of "groups" or reify them with explanations, because they represent evolutionary non-events [5]

A group whose identifying features evolved convergently in two or more lineages is polyphyletic (Greek πολύς [polys], "many"). More broadly, any taxon that is not paraphyletic or monophyletic can be called polyphyletic. Empirically, the distinction between polyphyletic groups and paraphyletic groups is rather arbitrary, since the character states of common ancestors are inferences, not observations.

These terms were developed during the debates of the 1960s and 1970s accompanying the rise of cladistics.

Paraphyletic groupings are considered problematic by many taxonomists, as it is not possible to talk precisely about their phylogenetic relationships, their characteristic traits and literal extinction. [6] [7] Related terms are stem group, chronospecies, budding cladogenesis, anagenesis, or 'grade' groupings. Paraphyletic groups are often relics from outdated hypotheses of phylogenic relationships from before the rise of cladistics. [8]

Examples Edit

The prokaryotes (single-celled life forms without cell nuclei) are a paraphyletic grouping, because they exclude the eukaryotes, a descendant group. Bacteria and Archaea are prokaryotes, but archaea and eukaryotes share a common ancestor that is not ancestral to the bacteria. The prokaryote/eukaryote distinction was proposed by Edouard Chatton in 1937 [9] and was generally accepted after being adopted by Roger Stanier and C.B. van Niel in 1962. The botanical code (the ICBN, now the ICN) abandoned consideration of bacterial nomenclature in 1975 currently, prokaryotic nomenclature is regulated under the ICNB with a starting date of 1 January 1980 (in contrast to a 1753 start date under the ICBN/ICN). [10]

Among plants, dicotyledons (in the traditional sense) are paraphyletic because the group excludes monocotyledons. "Dicotyledon" has not been used as a botanic classification for decades, but is allowed as a synonym of Magnoliopsida. [note 1] Phylogenetic analysis indicates that the monocots are a development from a dicot ancestor. Excluding monocots from the dicots makes the latter a paraphyletic group. [11]

Among animals, several familiar groups are not, in fact, clades. The order Artiodactyla (even-toed ungulates) as traditionally defined is paraphyletic because it excludes Cetaceans (whales, dolphins, etc.). Under the ranks of the ICZN Code, the two taxa are separate orders. Molecular studies, however, have shown that the Cetacea descend from artiodactyl ancestors, although the precise phylogeny within the order remains uncertain. Without the Cetaceans the Artiodactyls are paraphyletic. [12] The class Reptilia, as traditionally defined, is paraphyletic because it excludes birds (class Aves) and mammals. Under the ranks of the ICZN Code, these three taxa are separate classes. However, mammals hail from the synapsids (which were once described as "mammal-like reptiles") and birds are sister taxon to a group of dinosaurs (part of Diapsida), both of which are "reptiles". [13] Alternatively, reptiles are paraphyletic because they gave rise to (only) birds. Birds and reptiles together make Sauropsids, a clade of Amniota that is the sister group of the clade that includes mammals.

Osteichthyes, bony fish, are paraphyletic when circumscribed to include only Actinopterygii (ray-finned fish) and Sarcopterygii (lungfish, etc.), and to exclude tetrapods more recently, Osteichthyes is treated as a clade, including the tetrapods. [14] [15]

The "wasps" are paraphyletic, consisting of the narrow-waisted Apocrita without the ants and bees. [16] The sawflies (Symphyta) are similarly paraphyletic, forming all of the Hymenoptera except for the Apocrita, a clade deep within the sawfly tree. [14] Crustaceans are not a clade because the Hexapoda (insects) are excluded. The modern clade that spans all of them is the Tetraconata. [17] [18]

One of the goals of modern taxonomy over the past fifty years has been to eliminate paraphyletic "groups" such as the examples here from formal classifications. [19] [20]

Paraphyly in species Edit

Species have a special status in systematics as being an observable feature of nature itself and as the basic unit of classification. [21] Some articulations of the phylogenetic species concept require species to be monophyletic, but paraphyletic species are common in nature, to the extent that they do not have a single common ancestor. Indeed, for sexually reproducing taxa, no species has a "single common ancestor" organism. Paraphyly is common in speciation, whereby a mother species (a paraspecies) gives rise to a daughter species without itself becoming extinct. [22] Research indicates as many as 20 percent of all animal species and between 20 and 50 percent of plant species are paraphyletic. [23] [24] Accounting for these facts, some taxonomists argue that paraphyly is a trait of nature that should be acknowledged at higher taxonomic levels. [25] [26]

Cladists advocate a phylogenetic species concept [27] that does not consider species to exhibit the properties of monophyly or paraphyly, concepts under that perspective which apply only to groups of species. [28] They consider Zander's extension of the "paraphyletic species" argument to higher taxa to represent a category error [29]

Uses for paraphyletic groups Edit

When the appearance of significant traits has led a subclade on an evolutionary path very divergent from that of a more inclusive clade, it often makes sense to study the paraphyletic group that remains without considering the larger clade. For example, the Neogene evolution of the Artiodactyla (even-toed ungulates, like deer, cows, pigs and hippopotamuses - note that Cervidae, Bovidae, Suidae and Hippopotamidae, the families that contain these various artiodactyls, are all monophyletic groups) has taken place in environments so different from that of the Cetacea (whales, dolphins, and porpoises) that the Artiodactyla are often studied in isolation even though the cetaceans are a descendant group. The prokaryote group is another example it is paraphyletic because it is composed of two Domains (Eubacteria and Archaea) and excludes (the eukaryotes). It is very useful because it has a clearly defined and significant distinction (absence of a cell nucleus, a plesiomorphy) from its excluded descendants. [ citation needed ]

Also, some systematists recognize paraphyletic groups as being involved in evolutionary transitions, the development of the first tetrapods from their ancestors for example. Any name given to these hypothetical ancestors to distinguish them from tetrapods—"fish", for example—necessarily picks out a paraphyletic group, because the descendant tetrapods are not included. [30] Other systematists consider reification of paraphyletic groups to obscure inferred patterns of evolutionary history. [31]

The term "evolutionary grade" is sometimes used for paraphyletic groups. [32] Moreover, the concepts of monophyly, paraphyly, and polyphyly have been used in deducing key genes for barcoding of diverse group of species. [33]

Independently evolved traits Edit

Current phylogenetic hypotheses of tetrapod relationships imply that viviparity, the production of offspring without the external laying of a fertilized egg, developed independently in the lineages that led to humans (Homo sapiens) and southern water skinks (Eulampus tympanum, a kind of lizard). Put another way, viviparity is a synapomorphy for Theria within mammals, and an autapomorphy for Eulamprus tympanum (or perhaps a synapomorphy, if other Eulamprus species are also viviparous).

"Groups" based on independently-developed traits such as these examples of viviparity represent examples of polyphyly, not paraphyly.

Not paraphyly Edit

    are polyphyletic, not paraphyletic. Although they appear similar, several different groups of amphibious fishes such as mudskippers and lungfishes evolved independently in a process of convergent evolution in distant relatives faced with similar ecological circumstances. [34] are polyphyletic because they independently (in parallel) lost the ability to fly. [35]
  • Animals with a dorsal fin are not paraphyletic, even though their last common ancestor may have had such a fin, because the Mesozoic ancestors of porpoises did not have such a fin, whereas pre-Mesozoic fish did have one. archosaurs are not a paraphyletic group. Bipedal dinosaurs like Eoraptor, ancestral to quadrupedal ones, were descendants of the last common ancestor of quadrupedal dinosaurs and other quadrupedal archosaurs like the crocodilians.

Non-exhaustive list of paraphyletic groups Edit

The following list recapitulates a number of paraphyletic groups proposed in the literature, and provides the corresponding monophyletic taxa.

Paraphyletic taxon Excluded clades Corresponding monophyletic taxon References and notes
Prokaryotes Eukaryota Cellular organisms [36]
Protista Animalia, Plantae, and Fungi Eukaryota [37]
Invertebrates Vertebrata Animalia [38]
Sponge Eumetazoa Animalia [39] [40]
Worm Multiple groups Nephrozoa [41] [42]
Radiata Bilateria Eumetazoa [43]
Platyzoa Lophotrochozoa, Mesozoa Spiralia [44]
Fish Tetrapoda Vertebrate [45]
Reptiles Birds Sauropsida [46]
Lizard Snakes, Amphisbaenia Squamates [47]
Plagiaulacidans Cimolodonta, Arginbaataridae Multituberculata [48]
Pelycosaurs Therapsida Synapsida [49]
Even-toed ungulates Cetacea Cetartiodactyla [50] [51]
Archaeoceti Neoceti Cetacea [52]
Prosimians Simiiformes Primates [53]
Crustaceans Hexapoda Tetraconata [17] [18]
Wasps Ants, Bees Apocrita [54]
Sawfly Apocrita Hymenoptera [14]
Vespoidea Apoidea, Ants Euaculeata [55]
Parasitica Aculeata Apocrita [56]
Nautiloidea Ammonoidea, Coleoidea Cephalopoda [57]
Charophyte Embryophyte (Land plants) Streptophyta [58]
Bryophyte Tracheophyte Embryophyte [59] [58]
Gymnosperm Angiosperm Spermatophyte [60]
Dicotyledon Monocotyledon Angiosperm [11]
Moth Butterfly Lepidoptera [61]
Coral Medusozoa, Myxozoa Cnidaria [62] [63]
Jellyfish Hydroidolina Medusozoa [64] [65] [66]
Cycloneuralia Panarthropoda Ecdysozoa [67] [68]
Rotifera Acanthocephala Syndermata [69] [70]
Mecoptera Siphonaptera Mecopteroidea
Anthoathecata Leptothecata, Siphonophorae Hydroidolina
Monkey Hominoidea Simiiformes

The concept of paraphyly has also been applied to historical linguistics, where the methods of cladistics have found some utility in comparing languages. For instance, the Formosan languages form a paraphyletic group of the Austronesian languages because they consist of the nine branches of the Austronesian family that are not Malayo-Polynesian and are restricted to the island of Taiwan. [71]


Detecting selection with a genetic cross

Distinguishing which traits have evolved under natural selection, as opposed to neutral evolution, is a major goal of evolutionary biology. Several tests have been proposed to accomplish this, but these either rely on false assumptions or suffer from low power. Here, I introduce an approach to detecting selection that makes minimal assumptions and only requires phenotypic data from ∼10 individuals. The test compares the phenotypic difference between two populations to what would be expected by chance under neutral evolution, which can be estimated from the phenotypic distribution of an F2 cross between those populations. Simulations show that the test is robust to variation in the number of loci affecting the trait, the distribution of locus effect sizes, heritability, dominance, and epistasis. Comparing its performance to the QTL sign test-an existing test of selection that requires both genotype and phenotype data-the new test achieves comparable power with 50- to 100-fold fewer individuals (and no genotype data). Applying the test to empirical data spanning over a century shows strong directional selection in many crops, as well as on naturally selected traits such as head shape in Hawaiian Drosophila and skin color in humans. Applied to gene expression data, the test reveals that the strength of stabilizing selection acting on mRNA levels in a species is strongly associated with that species' effective population size. In sum, this test is applicable to phenotypic data from almost any genetic cross, allowing selection to be detected more easily and powerfully than previously possible.

Keywords: evolution genetic cross natural selection variance.

Conflict of interest statement

The author declares no competing interest.

Figures

The sign test and the v test. ( A ) Illustration of the…

Neutral simulations. Each panel shows…

Neutral simulations. Each panel shows 20 quantile–quantile (QQ) plots, each with 10 4…

Directional selection simulations. All panels…

Directional selection simulations. All panels show scatter plots where every point is an…

Empirical analysis. ( A )…

Empirical analysis. ( A ) Results for artificially selected traits in crops, livestock,…


How Darwin’s Theory of Evolution Changed the World

Evolutionary thinking is all around us. Anytime we visit a zoo or natural history museum, watch a nature program or read a science or wildlife magazine, we will likely be exposed to evolutionary concepts.

In most public schools and universities, evolution is a major part of the biology and science curricula. We&rsquore bombarded from nearly every avenue with the idea that life originated by chance and eventually developed into the organisms we see today.

It&rsquos had a major effect on our society. A 2019 Pew Research Center study reported that a total of 81 percent of American adults believe in evolution. This includes 33 percent who hold that humans evolved due to processes like natural selection with no involvement by a Creator, along with 48 percent who think human evolution occurred through processes guided or allowed by a higher power.

Rewind 160 years to the beginning of Darwin&rsquos theory of evolution

Historically speaking, the belief in evolution is a relatively new phenomenon. Throughout the history of Western civilization, people in most cultures believed that humankind and all forms of life were specially created by God (or other deities, albeit false).

It wasn&rsquot until 1859, when British scientist Charles Darwin published his book On the Origin of Species, that the public began to think otherwise. This was a major turning point in history, because it influenced people&rsquos decisions to turn their backs on God, the Bible and religion.

In his book, Charles Darwin outlined the basics of his evolutionary theory. He claimed that animal and plant species have changed over time and will continue to change, giving rise to new, more advanced species. He contended that evolutionary changes were a result of natural selection, meaning the organisms with the most advantageous inheritable traits survive and reproduce at a higher rate than weaker individuals, perpetuating the strongest variations and eliminating the unfavorable ones.

Eventually, Darwin reasoned, this could result in a species changing enough of its characteristics to develop into a totally new creature. He maintained that ultimately all life-forms are related, from finches to monkeys to tulips, sharing a common single-celled ancestor that existed millions of years ago.

Human beings weren&rsquot directly addressed in Origin of Species, yet Darwin was convinced that natural selection also applied to mankind. For that reason, he wrote another book. Darwin&rsquos The Descent of Man was published in 1871.

He stated his purpose in Chapter 2: &ldquoto show that there is no fundamental difference between man and the higher mammals in their mental faculties.&rdquo He insisted that humans are just another type of animal, not much different from the great apes, except for the acquisition of a few beneficial traits.

Charles Darwin wasn&rsquot the first to espouse evolutionary concepts. A number of scientists before him entertained the notion that species could evolve, but had no plausible hypothesis for what caused the changes. It was Darwin&rsquos theory of evolution by natural selection that provided the world&rsquos scientists and philosophers with the explanation to &ldquoprove&rdquo in their minds that evolutionary changes could occur and had indeed happened.

Paving the way for disbelief

Today evolutionists hail Charles Darwin as a hero of discovery. But for those who believe in God and that the Bible is His infallible Word, Darwin&rsquos ideas are hardly something to celebrate. Darwinism seeks to explain all the wonder, beauty and variety we see in nature without a supernatural Creator. For those who are so inclined, this means the whole concept of God can be done away with.

Darwinism seeks to explain all the wonder, beauty and variety we see in nature without a supernatural Creator. A move toward secularism started building in Europe during the mid-19th century, right about the time Darwin wrote Origin of Species. Secularism is the belief that mankind does not need God or His laws. It is based on the philosophy known as naturalism, meaning there is no spirit realm and physical matter is all that exists.

Secularists want religion and all references to God and the Bible out of schools, governmental bodies and public life. Darwinism provided them with the fuel to spread their ideology far and wide. Sadly, that&rsquos exactly what has happened.

Once the Bible is no longer the basis for understanding our lives, life ultimately becomes meaningless. The only purpose evolutionists can claim for human existence is survival&mdashto get whatever they can for themselves in this life (since they do not envision an afterlife) and reproduce and pass on their genes.

Naturalist Chet Raymo admits as much in his book Skeptics and True Believers (1998). He explains that Darwin&rsquos theory of evolution teaches that &ldquoour lives are brief and inconsequential in the cosmic scheme of things&rdquo (p. 110). He also proposes that Darwinism is a major reason the scientific community concluded years ago that, in the words of Steven Weinberg, &ldquothe more the universe seems comprehensible, the more it also seems pointless&rdquo (p. 154).

Evolutionists don&rsquot believe what the Bible clearly spells out: that God created mankind in His image (Genesis 1:27) with a special plan in mind&mdashto bring &ldquomany sons to glory&rdquo (Hebrews 2:10-11)&mdashand that the purpose for our lives is to prepare for future roles in God&rsquos eternal Kingdom.

What about theistic evolution?

Darwinism is opposed to God&rsquos truths. Yet there are those who try to integrate evolutionary theory with the biblical creation account. Known as theistic evolutionists, they believe God created the universe and everything in it, but did so using evolutionary processes over billions of years.

Both concepts can&rsquot be true. Trying to reconcile them leads to the idea that there wasn&rsquot a literal creation over a set period of time, and that the biblical creation account is merely metaphorical. This paves the way for disbelieving other parts of the Bible as well.

Like traditional evolution, theistic evolution reduces God&rsquos Word to insignificance and opens the door to ungodly thinking. (See our online article &ldquoTheistic Evolution.&rdquo)

Immorality&mdashthe unavoidable result of Darwin&rsquos theory of evolution

When society stops believing in God and the Bible, people start deciding for themselves how to live. They no longer recognize God&rsquos laws as binding or believe they are accountable to Him. The inevitable outcome is a decline in morality.

Some people are actually drawn to evolution because it gives them a reason to not believe in God and thus free themselves of moral restraints.

Writer and philosopher Aldous Huxley, an ardent proponent of Darwinism, stated candidly in his 1937 essay Ends and Means: &ldquoFor myself as, no doubt, for most of my contemporaries, the philosophy of meaninglessness was essentially an instrument of liberation. The liberation we desired was &hellip from a certain system of morality. We objected to the morality because it interfered with our sexual freedom.&rdquo

The apostle Paul addresses this mind-set in Romans 1:28-29. He warns us that rejecting God leads to a &ldquodebased mind&rdquo and, in turn, unrighteousness, sexual immorality, wickedness, covetousness, maliciousness, envy, murder, strife, deceit and evil-mindedness.

There are other ways, too, that espousing Darwinism can lead to ungodly behavior. Some reason that if mankind is evolving, it follows that what&rsquos right and good also changes. Therefore, morality must be relative to the conditions of life at any given time&mdashspurring the thinking that there are no fixed rules we must live by.

Social Darwinism

Others have applied Darwin&rsquos biological theory to how people interact with each other. This is known as social Darwinism. The thinking is, if animals and plants are locked in a struggle for existence, preserving the strong and eradicating the weak, this same process of &ldquosurvival of the fittest&rdquo also applies to societies.

Social Darwinism has been used to try to excuse some of mankind’s most corrupt and vile practices, including cutthroat business competition, corporate greed, eugenics, racism and genocide. Social Darwinism has been used to try to excuse some of mankind&rsquos most corrupt and vile practices, including cutthroat business competition, corporate greed, eugenics, racism and genocide. These have all been justified under the guise of it being natural to exploit, crush and eliminate weaker individuals and businesses.

The most infamous application of social Darwinism was when Adolf Hitler tried to justify killing millions of Jews&mdashwhom he saw as &ldquounfit&rdquo&mdashand establish his master Aryan race.

Darwin himself was critical of society&rsquos efforts to help the impoverished and sickly. He wrote in Chapter 5 of The Descent of Man that these practices were &ldquohighly injurious to the race of man.&rdquo Darwin believed natural selection should be allowed to run its course for those who were destined to be eliminated. That is the terrible, but logical conclusion of Darwinism.

Nothing &ldquoright&rdquo about evolution

The truth is, nothing good can come from accepting Darwin&rsquos theory of evolution or its modern adaptations. It is a cruel, depressing and hopeless approach to our existence. Without knowing that we have a loving God who&rsquos in control and that there&rsquos an incredible purpose to our lives, it is impossible to have a truly positive outlook.

Moreover, no culture can survive when individuals make their own rules and live for themselves.

Ruthless competition at the expense of others is the exact opposite of how God wants mankind to live. The Bible instructs the strong to help the weak (Romans 15:1-3).

The other major problem with Darwin&rsquos theory of evolution is that it&rsquos unprovable. If evolution were true, there should be abundant evidence in the fossil records of transitional forms between species and proof of new species developing in the wild&mdashbut there isn&rsquot. The only proof has been for microevolution&mdashadaptation, or minor changes within existing species&mdashwhich we do not dispute. (See our online article &ldquoMicroevolution vs. Macroevolution.&rdquo)

Furthermore, neither Darwin nor any other scientist has been able to come up with a credible answer for where the original single-celled organism came from.

Still, many people cling to the idea of evolution and insist it&rsquos true. This is to be expected. Romans 8:7 says that &ldquothe carnal mind is enmity against God.&rdquo Human nature would rather believe there is no God and no purpose for life, rather than submit to a higher power.

The Bible tells us that &ldquoscoffers will come in the last days&rdquo (2 Peter 3:3). There will be those who doubt God&rsquos existence and ridicule those who don&rsquot believe in evolution, right up until the time Christ returns.

But that&rsquos when the scoffers and all of mankind will learn the truth&mdashthat we do have a Creator, and submitting to Him is the only way to a truly happy, meaningful existence.