More Muddled Evolution Theory

December 16, 2008    By: Jacob J @ 12:00 am   Category: Uncategorized

I am a pro-science guy and I believe in evolution. That said, it seems to me from watching the Discovery channel and reading popular science articles that it is easy to get carried away explaining things based on evolution to the point that we forget what evolution is in the first place.†  Evolution is natural selection working on random mutation. Here’s an example from the NYT (hat tip: ZD sidebar) demonstrating how easy it is to slip from sound scientific reasoning into poppycock:

Monogamy evolves when stable couples are more successful at rearing offspring than, say, a female on her own, or a family group. Judging by the low frequency of monogamy in nature, this is rarely the case.

The reasoning here is based on the notion that if something would be selected for by natural selection, it will therefore arise in nature. That, of course, is ridiculous. To illustrate, here is a statement based on identical logic:

The ability for humans to breathe fire evolves when fire-breathers are more successful at rearing offspring than, say, non-fire-breathers. Judging by the low frequency of fire-breathing humans in nature, this is rarely the case.

Just because some trait would be useful, it does not follow that evolution will ensure that this trait “evolves.”  I was going to say that this sort of mistake would never be made by an actual scientist but arises when non-scientists try to write popular science articles. Then I looked up the bio for the author of that NYT article.

Olivia Judson (born 1970) is an evolutionary biologist at Imperial College London. Judson, who is the daughter of science historian Horace Freeland Judson, was a pupil of W.D. Hamilton. She graduated from Stanford University, gained a doctorate from Oxford, and worked for some time as a journalist before becoming a research fellow at Imperial College London. (wikipedia)

Am I missing something, or is this just another example of how easy it is to muddle the details of what evolution really explains when you spend all day opining about it.

Kiskilili’s post is also relevant to this point.


  1. It is easy to slip from nuance to simplification to just sort of wrong.

    Comment by Stephen M (Ethesis) — December 16, 2008 @ 5:53 am

  2. Is the idea that monogamy evolves as a memetic idea or as a genetic one? Or is it some combination of the two?

    Comment by Matt W. — December 16, 2008 @ 8:11 am

  3. First of all “monogamy” does not evolve at all–a monogamous instinct is what evolves. Another thing a scientist should be more careful about.

    Besides that, however, I think the logical flaw is different than the one you point out. You basic claim is correct–namely that usefulness does not necessarily imply that a trait will actually evolve. But firebreathing cannot be compared to a monogamous instinct because the latter has demonstrably evolved in some species, while the former has not. So one might legitimately wonder why a trait such as a monogamous instinct has evolved in some circumstances, while it is pointless to wonder why firebreathing has never evolved anywhere.

    The real logical flaw is that the rarity of the monogamous instinct in nature is entirely irrelevant to any discussion of human behavior because humans occupy a particular ecological niche within which different traits might be advantageous than in niches occupied by other creatures. (Upon reading the NYT article, it seems clear that the writer understands this, so I don’t why she makes such a point of highlighting the rarity of monogamy). The point of the NYT article is that it might be possible to artificially give people a monogamous instinct. So to me, the real scientific question is whether the monogamous instinct in males (as opposed to a polygamous or promiscuous instinct) is a superior adaptive trait within the ecological niche occupied by humans. I don’t think science (much less this particular article) has adequately addressed that question, so the issue of taking a shortcut to that trait is way premature (from a strictly scientific standpoint).

    Comment by Last Lemming — December 16, 2008 @ 8:15 am

  4. People will go on endlessly about what a great body of scientific thinking evolution is, yet when it comes to pondering what the implications of evolution are for the human species as presently constituted, the most common response is for the cheering to devolve into mutters. “Oh, never mind . . .”

    Comment by John Mansfield — December 16, 2008 @ 8:25 am

  5. For humans, the power of biological evolution is decreasing rapidly relative to the power of technological evolution. Also, to some extent, natural selection is being replaced with communal selection — although natural selection will perhaps always play a role in human evolution at the greatest environmental magnitudes, such as those affected by global or broader catastrophic risks.

    Comment by Lincoln Cannon — December 16, 2008 @ 10:44 am

  6. John, there actually are some very interesting investigations on human evolution in recent times. Some are related to say the ability to digest milk in communities that domesticated animals. Then there are things like the independent evolution of sickle-cell amenia to deal with malaria. There are others of that sort with many examples of evolution being fairly recent. (Say the last 15,000 years)

    For current evolution there are some arguments that human evolution is actually accelerating. The evidence isn’t all in, from what I can see. But I think it undeniable that things like medical care and intermixing of groups once largely separated is giving evolution the ability to deal with new situations as well as changing the kinds of influence natural selection has to work with.

    I suspect once sequencing individual genomes becomes cheap enough to be commonplace that we’ll gain a much better appreciation for how evolution is acting on humans the last few thousand years and today.

    Comment by Clark — December 16, 2008 @ 12:33 pm

  7. Matt,

    I think the idea is that it evolves genetically. Here is a quote from the article:

    A full understanding of the genetics of attachment is still some way off. But one of the genes that has already been implicated is the arginine vasopressin receptor 1a gene.

    Your question is a very important one since the nature/nurture debate comes front and center every time someone simply assumes that everything can be explained genetically. I think it is worth noting that natural selection can select for memetic behaviors as easily as it does genetic ones.

    Comment by Jacob J — December 16, 2008 @ 5:01 pm

  8. Last Lemming,

    So one might legitimately wonder why a trait such as a monogamous instinct has evolved in some circumstances, while it is pointless to wonder why firebreathing has never evolved anywhere.

    I don’t know, I can replace firebreathing with plenty of alternates that do occur in nature but make the point equally well. Why haven’t humans evolved tough skin to protect against injury, or wings for flying, or better night vision? Is it because these are not useful for promoting survival/reproduction or is it simply because evolution relies on random mutation and you don’t always get what might be useful.

    I see this argument applying directly to your question about why monotony as arisen in some circumstances and not others. One really obvious possibility is that the random mutation generator created it in one circumstance and not the other one we are comparing to. If that is the case, we learn nothing, and I don’t see how this can be ruled out.

    On your last paragraph beginning “the real logical flaw” I totally agree. Very good analysis.

    Comment by Jacob J — December 16, 2008 @ 5:10 pm

  9. Some argue that there is a problem of too much assumption that natural selection is responsible for everything. A number of scientists, including the late Stephen J. Gould, have pushed back at the notion that all evolution is by natural selection. Chance and contingency are important too. In fact, the smaller a population is, the greater the role chance plays.

    On the other hand, I don’t find the quote as offensive as you. I don’t read her to be saying that if monogamy is useful it will evolve. Rather, when it does (rarely) evolve it is because it is more useful (metaphorically speaking, of course) than the norm. That seems like a reasonable presumption to me.

    Comment by Jared* — December 16, 2008 @ 6:12 pm

  10. I see this argument applying directly to your question about why monotony has arisen in some circumstances and not others.

    Freudian slip?

    Comment by Nate W. — December 16, 2008 @ 9:30 pm

  11. Jared,

    Thanks for the comment about Gould. Acknowledging the significant role of chance is important I think.

    On the quote: You are correct about what she is saying, but she goes far beyond the non-controversial point you summarize. She says:

    Judging by the low frequency of monogamy in nature, this is rarely the case.

    From the low frequency of monogamy in nature, she concludes that it is rarely the case that stable couples are more successful at rearing offspring. You simply cannot get from the evidence to her conclusion without the assumption that when it is useful it will evolve.

    Comment by Jacob J — December 16, 2008 @ 10:32 pm

  12. Nate, I knew someone would pick up on that, couldn’t resist.

    Comment by Jacob J — December 16, 2008 @ 10:33 pm

  13. I agree with Jacob J’s perspective on natural selection: It’s clear that we don’t evolve every trait that would be useful, and it’s folly to conclude that a trait isn’t useful simply because it has not evolved in a population.

    But I also agree with Jared* in #9: Ms. Judson doesn’t seem to be saying that monogamy is not useful because it hasn’t evolved; she is merely saying that monogamy will evolve when it is useful enough to increase the chance of survival.

    Here is a real-life practical example of how something very useful may not evolve in the presence of a competing trait:

    In Neil Shubin’s book Your Inner Fish, he explains how all mammals have essentially the same olfactory sensors, but in species with rich color vision (like humans), most of these sensors have mutated to the point where they are no longer useful for smelling. The presumption is that rich color vision has proven to be more useful for survival than highly functional smell. So natural selection keeps the sense of smell sharp in many species. But in species with rich color vision, smell is less important for survival, so mutations can more ealisy arise and compound over time. Dolphins (which are also mammals) have olfactory sensors that have mutuated completely beyond use, presumably because they are of no use in the water, so there is no force of natural selection keeping that trait sharp.

    Comment by CE — December 17, 2008 @ 2:46 pm

  14. CE,

    I am totally baffled by your comment. Help me understand the distinction you are making between these two positions:

    It’s clear that we don’t evolve every trait that would be useful

    she is merely saying that monogamy will evolve when it is useful enough to increase the chance of survival.

    I must be missing an important nuance, because I agree with your first sentence but strongly dispute the second one.

    Comment by Jacob J — December 21, 2008 @ 10:43 am

  15. There is, wrapped up in this, the assumption that only useful traits evolve. That’s simply not true—even if natural selection were the only force driving evolution and environmental conditions never changed. Some traits are undesirable by-products of the development of other beneficial traits, whereas other traits arise by chance (as Jared* notes).

    Comment by BrianJ — December 21, 2008 @ 12:06 pm