Another look at falsehoods about evolution.

We previously addressed the falsehood “Evolution has stopped for humans” and concluded that background change in allele frequency independent of natural selection does not just stop for any viable, continuing population. So, no, saying that “evolution has stopped for humans” is tantamount to saying that “gravity has stopped for my coffee cup” (which is sitting here on my desk minding its own business).

But this question is a falsehood at another level. In reality, there are two additional questions that are actually being asked when this question is brought up:

  • Aren’t humans no longer subject to natural selection?; and
  • Aren’t humans not likely to give rise to a new species?

The first assertion is a widely held belief with absolutely no foundation, so it qualifies as a true Falsehood. The second question is not so widely discussed. Here, we’ll focus on the first and leave the second for another time.

Are human beings “still” subject to natural selection? This is a loaded question: Loaded with tricky words like “are” and “still” and “selection” and “human being.”

Let’s start with the Are-Still problem. A species is an entity that has temporal (time) and spatial (geography) dimensions. So an expanding population/species covers more and more geography over time, and so on. The “Are-Still” part of this question must be referring to some part of that time-space continuum. I think what is usually meant by “humans” is humans in this modern world of medicine and dominance over the environment, etc. In particular, it means humans as a population not subject to scarcities of food, ravages of predation, and suffering by disease. This is because in many people’s minds evolution roughly equals natural selection and its effects, and natural selection roughly equals these listed aspects of the environment and their effects. The struggle for existence, the competition for food, and so on. And the struggle is over. (Remember, we’re talking Fallacies here … )

The other biggie, sexual selection, is often left out of the discussion. The popular mindset often seems to lack a concept of human mate competition or mate choice as factors in human evolution or human affairs in general. I think this is due to modern conceptions of monogamy. We fool ourselves into thinking that since there is the same number of men and women. and everybody eventually gets married to a member of the opposite sex, etc. , then there really is no mating competition or sexual selection. (Not true, not true, and not true.) This is a deeply fascinating set of assertions, beliefs, fallacies, and innuendos. Almost everything in evolution is about food and sex. But let’s deal with the food first, and save the sex for later. (Always a good plan.)

So “Are-Still” part of this fallacy addresses a particular temporal-spatial chunk of “Human Beings.” What about selection? Here the very simple (and meaningful but nowhere complete) answer is this: If we have removed with modern medicine, agriculture, and deadly weapons the parasites, predators, and food limitations from our environment, that does not mean that we are not evolving. What it means is that a large number of selective forces have shifted. Since we are talking mainly about stabilizing selection related to the ability to find food, avoid predators, etc. (maybe some directional selection as well), this mostly means that we are experiencing “relaxed selection.” This is when selective forces that were there are no longer there (relaxed).

Many people confuse this with “not evolving.” But remember our earlier discussion. “Evolution is change in allele frequency over time.” And remember that mutations are common, and that most of them are weeded out. So relaxing selection almost always has to result in increased rates of evolution. So not only are humans not “not” evolving, human evolution may be accelerated in some areas of the genome. What a time to be alive!

But there is, as you may already be thinking, another big problem with this. The “Are-Still” construct in combination with the environment being less “red in tooth and claw,” and all that, is problematic. And here we are going to get to the part of this discussion where many people will get mad at me. Sorry, but the assertion that we are not evolving because we have solved all of these problems is racist, classist, and Westernist. You are a bad person for thinking these things. But that’s OK, we still love you and you can change.

Different human populations are very closely related to each other, reflecting both recent separation of those populations and long term flow of genes across populations that believe falsely themselves to be separate. There are people right now living in some far off part of the world, whom you’ve never heard of (nor they of you) who are among the most genetically distant from you right now, among whom are individuals who’s great great great great grandson or granddaughter are going to have sex with your great great great granddaughter or grandson and thusly produce offspring. How do I know that? Because I traveled way back in time in an imaginary time machine I keep around for thought experiments, and made that prediction 100 years ago, 1000 years ago, 10,000 years ago, and 30,000 years ago and every time I was correct.

The modern human genome is fluid, it has been fluid for tens of thousands of years, and it will be fluid for whatever future exists until either the sun explodes or somebody really screws up and sends us into extinction.

Right now, as I’m sure you know, a huge part of the earth’s population of humans does not have protection by modern wonders of science from parasites. A lot of people in Uganda are eaten by lions each year. People often starve. In other words, the usual selective forces are very much at work in our species, somewhere, indeed, in many places. Many different forces of selection are at work to differing degrees in different parts of the world and at different times (leading to genetic diversification?) and gene flow is ongoing across the planet (leading to genetic variability that defies sub speciation?)

It was possible, maybe, 25 years ago or so, to incorrectly but convincingly hold up Western Culture and Civilization as the place/time where many of the environmental forces of selection have been reduced. However, more and more people each year living in Western Civilization are less protected because of increase poverty and a widening gap between the “haves” and the “have nots.” On top of that, some of the ravages of nature that we thought we were protecting ourselves from (like bacteria and viruses) are co-evolving with our defenses. And, presumably, or defenses are co-evolving as well. Yet another factor is the novelty of the environment. Some populations may have gotten out of being eaten by lions or running out of food, at least for the time being. But these populations have likely run into other problems. Obesity results in morbidity and mortality and may affect fertility or reproductive success in various ways. Obesity is growing to an epidemic in the US right now. Obesity as a consistent feature starting in childhood will certainly have selective effects. How can it not?

There are probably dozens of effects of “civilization” that have their own selective stories. So Natural Selection is still very much at work in the usual ways. Natural Selection in some areas is relaxed, thus changing evolutionary rates and trends, and not by any means eliminating them. And Natural Selection is working in relatively novel ways through the effects of changes in the environment caused by modernization.

So… Hypothesis: “Human beings are no longer subject to Natural Selection.”

Falsehood Falsified.

More Falsehoods !!!

This post is one of a series on the topic of falsehoods. The following is a list of falsehoods posts in order:

Comments

  1. #1 DrugMonkey
    August 24, 2009

    Well put, holmes, very well put.

  2. #2 Jason Thibeault
    August 24, 2009

    What about the assertion that science can have a dampening effect on some selection criteria? This seems reasonable to me. The side effects may end up with other selection criteria popping up that were heretofore unanticipated, but to say that science *can* dampen natural selection is intuitive at least.

  3. #3 Jason Thibeault
    August 24, 2009

    Sorry, closer reading shows you dealt with this claim directly, saying it shifts around the selection criteria. Though this was what I said in the last thread, and you said was also a fallacy. So… hmm.

  4. #4 Jim Thomerson
    August 24, 2009

    Positive growth of a population, which was not growing before, is evidence that the population is subject to reduced natural selection. This is the case with humans, whose rate of population growth has skyrocketed over the past century or so. The interesting thing is that the highest rates of growth have not been in the “developed” world, where one would think selection the most relaxed.

  5. #5 noel
    August 24, 2009

    While your analysis is technically correct, isn’t it also the case that genetically unfit individuals, like radio talk show hosts and Republicans, are currently allowed to reproduce, thereby polluting the genome and dooming us all?

  6. #6 Rob
    August 24, 2009

    Should post this stuff on MythBusters

  7. #7 Deen
    August 24, 2009

    Noel: it’s a fallacy to think evolution must lead to what we think of as improvement. Think blind cave fish. Right wingnuts losing their higher brain functions might be similar.
    ;).

  8. #8 John McKay
    August 24, 2009

    Without testing, how can you be sure gravity is still working on your coffee cup? Maybe it stays put because of inertia, static cling, a certain stickiness because you don’t clean your desk often enough, or because the cup is too depressed to fly.

  9. #9 glenn smith
    August 24, 2009

    One of my daughters favorite sayings. “Stupidity kills, just not fast enough.”

  10. #10 Nathan Myers
    August 24, 2009

    Eugenicists like (indeed, fetishize) the “natural selection has ended” fallacy because they fantasize about picking up the slack by culling the herd personally. Hannibal Lecter is the quintessential eugenicist.

  11. #11 HP
    August 24, 2009

    You hint at this in the original post, but it bears emphasizing that the selective pressures on humans in developed nations are different from parasites and lion attacks, but no less real. Heart disease, obesity, cancer, type II diabetes, COPD, and many other illnesses that plague Western-style bourgeois populations are so widespread today because the conditions that lead to them were so rare in the past, and most people reproduced before they manifested. That’s not so true anymore. Look at the burgeoning rates of type II diabetes in South Asian immigrants to the West, and, increasingly, in South Asia, as the South Asian middle class grows.

    Assuming that civilization doesn’t collapse in the short run, I would expect those illnesses to decrease in the next 10,000 years not so much because of the advance of medicine, but as a consequence of natural selection. OTOH, my confidence that Western-style civilization won’t collapse in the near term is nearly nil, so we have that to look forward to.

  12. #12 Jon Young
    August 24, 2009

    Ever watch idiocracy? Human evolution at it’s finest.

    “It’s what plants CRAVE!!”

  13. #13 Matt Springer
    August 24, 2009

    I think in fact there’s a deeper level of misunderstanding that some people have that causes this misconception. The catchphrase “survival of the fittest” makes it sound like survival is the issue – if you don’t get killed there’s no selection pressure. But in fact mere survival by itself means nothing. It’s all about reproduction. So far as natural selection is concerned the “fittest” person in the world will pass on no genes if s/he uses birth control throughout life. The next generation will not inherit genes from that person.

  14. #14 Greg Laden
    August 25, 2009

    Matt: Right, that deserves an entire falsehood essay all by itself.

  15. #15 Xenithrys
    August 25, 2009

    Glenn @ 9:

    Would your daughter mind if I edited that to “Stupidity kills, just not early enough.”?

  16. #16 Christopher Pollock
    August 25, 2009

    I’ve often thought that the widespread availability of contraception must be exerting a huge selective pressure in the wealthy part of the world. People who could afford to comfortably raise 6 children often only have 1 or 2, or even none at all.

    A normal sex drive used to be enough to produce a large brood, but this is no longer the case. It’s a simple case of previously adaptive behaviour becoming maladaptive in the face of a novel environmental feature.

    It seems obvious that natural selection will now strongly favour people who have a strong desire to have children, so long as the desire has at least some genetic basis. In a few hundred years people who don’t love children may be as rare as people who dislike sex are today. (Although, oddly, the latter do exist.)

  17. #17 APic
    August 25, 2009

    It seems obvious that natural selection will now strongly favour people who have a strong desire to have children, so long as the desire has at least some genetic basis. In a few hundred years people who don’t love children may be as rare as people who dislike sex are today. (Although, oddly, the latter do exist.)

    So, what about homosexuals? How are they favoured via natural selection?

  18. #18 Greg Laden
    August 25, 2009

    Human sexuality is extraordinarily complex and situationally adaptive. Think of it like cuisine. If something happened to make people not want to eat tomatoes, there would be fewere and fewer tomato eaters until there were none. Would the tomato eating gene be gone? No. There is no tomato eating gene.

  19. #19 Greg Laden
    August 25, 2009

    How do homosexuals exist given a Darwinian world??????????? OK, we can blog about that. Look for it.

  20. #20 noel
    August 25, 2009

    Homos exist because we help our less stylish sisters select clothes and make-up that makes them more attractive. I mean, they have some of the same jeans.

  21. #21 Jared
    August 25, 2009

    Oo, oo, I know! You’re the anthropologist, though, so have fun…

  22. #22 R.G. Frano, A-EMT-4-P, (Ret.)
    August 25, 2009

    Nuclear, {power & weapons} & other W.M.D.’s are just one of the issues that still place humans totally under nature, rather then the other way around.
    As for human’s ‘speciation’…wouldn’t humanity have to moved some portion of itself to Mars, (or the ‘Vatican’, an even more remote location, {L.O.L.!}), to isolate that portion over enough, (‘geologic’) time to see, a
    ‘different’ humanity emerge?

  23. #23 R.G. Frano, A-EMT-4-P, (Ret.)
    August 25, 2009

    Nuclear, {power & weapons} & other W.M.D.’s are just one of the issues that still place humans totally under nature, rather then the other way around.
    As for human’s ‘speciation’, wouldn’t humanity have to moved some portion of itself to Mars, (or the ‘Vatican’, an even more remote location, {L.O.L.!}), to isolate that portion over enough, (‘geologic’) time to see, a ‘different’ humanity emerge?

  24. #24 Mara McDonald
    August 25, 2009

    Selection works most effectively when resources are limiting and competition for those resources is enhanced. Thus, the growth in human populations does not mean that there is no selection on humans, but that the competition for resources in some areas have been shifted to a new level, or carrying capacity. Food was once a limiting resource, but with the Green Revolution, no longer was a limiting resource (except where inequities in resource distribution occur). Wiens and Rottenberg back in the 1970′s (?) showed that shrubsteppe bird species exhibited strong seletion once every few years, not every year. Work on Galapagos finches by Peter and Rosemary Grant also demomnstrate that selection is episodic, and not continuous. The existence of wars is evidence that resources are limiting.

  25. #25 doug
    August 25, 2009

    Greg and others,

    homosexuals exist because a)sexual orientation is complex, involving the expression of different genes, not just a single on and off switch, and b) sexual preference by itself doesn’t determine likelihood of reproduction. In a clan/tribal society, such as prevailed in the pre-industrial world and still widely exists, marriage and mating behavior were not at the sole discretion of individuals. It was often (and still is) decided on the basis of access to resources, alliance advantages and other reasons not directly related to the personal choice of the individuals involved.

    Taken together, its fairly clear that homosexuality is not a simple trait that is easily filtered out of the gene pool by natural or sexual selection processes.

    Some studies have indicated that high hormone levels that related to hyper-sexuality (more manly or more womanly) also lead to lower reproductive capability and higher incidence of other health problems. So some stable level of homosexuality may in fact be advantageous to the overall genetic health of the population

  26. #26 Greg Laden
    August 25, 2009

    The best evidence we have strongly suggests that food was not a limiting factor for humans in a very very long time. The invention of horticulture certainly increased food stress in many populations at first, and after that it was a mixed bag.

  27. #28 Greg Laden
    August 25, 2009

    Jim: Nice link, but what does it mean?

  28. #29 Thomas Krawford
    August 25, 2009

    I agree with everything said thus far, but why not consider taking the question a little further.

    Evolution is both a word and a point of scientific fact, but its not necessarily an accurate term . For instance, let’s look at all life as a series of interlocking but hierarchical systems that change not only because of inherent design, but integration of design variations relative to the host environment.

    In other words, in any given living system, change is necessary: that which is there before the process of evolution. What we believe is evolution is probable: that is, our understanding of what evolution does and does not do over a period of time is constructed from our common understanding of environmental change relative to general and specific stasis.

    And there is the constancy of occurrence of either in joint, direct or inverse relation to the other, relative to the greatest common general circumstance of simple change or complex evolution and the least common individual result of evolution and change integration.

    Homosexuality, or any sexual identity thus arises within our human system, not because of an inherent gay gene, but because of an inherent probability of the overall system to generate variations that add to the system’s stability and longevity relative the host environment over a given period of time and selection.

    It sounds like I’m nitpicking, but I’m working on an overall idea that this line of reasoning directly relates to.

    Thanks
    Thomas

  29. #30 Greg Laden
    August 25, 2009

    Thomas: At the base, just because something exists (a trait, a behavior) does not mean that there is a direct genetic link.

    To understand human homosexuality one merely has to understand that sexuality in humans is only occasionally about having babies. In other animals where bonding, erotic behaivor, sex, is also not always directly about getting the sperm and egg together, we also see lots of “homosexuality”.

    When it comes to homosexuality, the “sexuality” part is the part that is selected for in an evolutionary sense. The “homo” part is icing.

  30. #31 David S
    August 25, 2009

    While the genes of a male homosexual aren’t passed on to his decedents (because he normally does not reproduce), it is likely that his siblings also have the same genes. So it might be the case that having a homosexual brother might increase your ability to reproduce and pass on those genes to your descendants.

    For example, the gene might promotes attraction to men. In men this manifests as homosexuality, but in women manifests as having more offspring. The net effect might be an advantage. See:
    http://www.reproductive-revolution.com/female-fecundity.html

  31. #32 Monado, FCD
    August 25, 2009

    Also, an unmarried sibling can be a big help in raising a family.

    I imagine we’re evolving the ability to live with more people, in more crowded conditions, to handle more complex interactions, e.g. knowing more than a hundred people, to delay gratification and to resist the urge to overeat and underexercise in times of ease and plenty.

  32. #33 Jim Thomerson
    August 25, 2009

    I know of at least two instances where homosexual men were married and fathered children before coming out of the closet. Homosexuals do reproduce. Inclusive fitness is a measure of how many copies of your genes get passed on to the next generation. We all know of examples where childless individuals have contributed to the success of relatives, who bear copies of some of their genes.

  33. #34 Christopher Pollock
    August 25, 2009

    Greg: I honestly have no idea why homosexuals exist. It is perhaps the greatest unsolved riddle in human sexuality.

    I’ve read about quite a few hypotheses, but none of them sound very convincing. If you can explain it, I’d very much like to know about it.

  34. #35 Nathan Myers
    August 25, 2009

    I’m fairly satisfied with the answers so far, although I crave detail. But the answers seem, also, to apply mainly to male homosexuality. Historically women have often enough not had a choice about whether or with whom to reproduce, regardless of their preference.

  35. #36 Karl
    London
    July 23, 2012

    Selection certainly does still have an effect humans, however from experience, there are a number of people who are not necessarily happy with the direction in which natural selection is taking. Fitness is directly correlated with fecundity, and the individuals who produce most offspring are not usually the same individuals who contribute most to society.
    @Mara. Precisely. Though eventually food, water or land will become a limiting factor upon human population growth, until humans either establish a space (Mars?) colony, or some tragic event reduces the human population significantly (or sends us into extinction) The large size of the human population base gives a better potential for faster evolution, and survival should such an event occur.

  36. #37 Anonymous
    July 26, 2013

    The idea of more reproductive success for organisms with certain traits which would cause said traits to be passed on and made more common being applied to humans today is retarded. Sorry, but very nearly every one of us can reproduce at some point regardless of our fitness for it. Maybe humans are just that perfect. Or maybe you’re applying hardline science where subjectivity does not exist to one of an extremely small number of species that doesn’t choose who to mate with based on genetics or fitness, but on subjective values. Maybe we can attribute our astonishing and never-ending population growth to our free will which we likely developed through a very successful evolution of some type, but I’m really not seeing natural selection hitting us very hard nowadays (non-existent man-eating lions eating everyone in Uganda aside). I also noticed someone mentioning people who say it doesn’t apply are eugenicists. I’d have to argue the opposite. Supporting the idea that natural selection still has an effect on humans today and can’t be changed could be seen as support for not allowing “unfit” individuals to breed because that would weaken the species and go against the infallible law of survival of the fittest.

  37. #38 Neptune
    January 14, 2014

    Human as species has evolved social and technological advanced that rule of natural selection does not apply. If it be technological advanced human society can wipe out other society with Nuclear Bomb/technology and be justified. Then Hiroshima and Nagasaki will be justified. By our social evolution we are supporting deaf dumb and people in vegetative state who otherwise would have been wiped out by natural selection. So social species reduces natural selection process.