The Absurdity of “Just So Stories” in Explaining Evolution

And the Camel said ‘Humph!’ again; but no sooner had he said it than he saw his back, that he was so proud of, puffing up and puffing up into a great big lolloping humph.

‘Do you see that?’ said the Djinn. ‘That’s your very own humph that you’ve brought upon your very own self by not working. To-day is Thursday, and you’ve done no work since Monday, when the work began. Now you are going to work.’

‘How can I,’ said the Camel, ‘with this humph on my back?’

‘That’s made a-purpose,’ said the Djinn, ‘all because you missed those three days. You will be able to work now for three days without eating, because you can live on your humph; and don’t you ever say I never did anything for you. Come out of the Desert and go to the Three, and behave. Humph yourself!’

~Rudyard Kipling, How the Camel Got His Hump.

Although we all realize that the camel didn’t get its hump out of laziness and that this is just a cute children’s story designed to impress upon kids the value of honest work, some days I’m not so sure that current theories about adaptation aren’t far off the same mark.

The great Stephen Jay Gould referred to these hypotheses concerning adaptation of features as “Just So Stories,” named after the popular children’s book by Rudyard Kipling that, through a series of charming tales, told how different animals acquired their unique features, such as the camel and his hump.

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While modern hypotheses may seem a little less far-fetched, they are no less fanciful– in part because modern scientists are sometimes so focused on “What adaptive advantage could this trait possibly give?” rather than determining how said trait could have arisen and been passed down by other means. In addition, so often these hypotheses are untestable, so in actuality they’re not even “hypotheses”. They’re just interesting thoughts.

My biggest complaint about these “interesting thoughts” is why we insist that a single physical trait be acted upon directly as if it exists in a morphological vacuum. For instance, just the other day I wondered to myself, “Why do humans have such long hair?” We have the longest hair of any mammals– especially of those naturally occurring. While I wanted a causal reason for the increase in relative hair-growth (e.g., mutations in Genes X , Y, Z lead to a prolongation of the phase of anagen in humans), instead I found posts by evolutionary biologists positing that it was an adaptive development to deal with the cold. (By their measure, long versus shorter hair would’ve meant the difference between life and death!)

But here’s another thought. So often the genes that control structural development– the aspect that is most easily observed in the fossil record– are involved in many organ systems, not individual organs. (Individuals with congenital malformations often have complex combinations of multiorgan malformation, including skin and hair malformations.) And so, if we absolutely must call upon adaptation to explain a feature’s subsistence, why did positive selection have to act on that particular feature alone? Why couldn’t it have acted on a related feature and the one of interest just happened to have gotten taken along for the ride, especially if it was neutral or only mildly deleterious in nature? For instance, wouldn’t it be more likely that long hair was simply an evolutionary oh-well that occurred alongside another more adaptive feature, e.g., changes to the brain or bipedalism? I would certainly think so.

But in that way, we’ll never know, because we weren’t there to see how it all happened. And that’s a major scientific danger in using an adaptationist paradigm to try to explain why change occurred. Trying to tease out such specifics from so little information is just blowing hot wind. It’s much easier to figure out how change occurred and work from there.

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In contrast to the adaptationist paradigm, Gould also reiterates in his book, The Structure of Evolutionary Theory, that major changes across species over time may be more strongly affected by something known as allopatric speciation, which is essentially the isolation of a subpopulation from the original population, leading to a divergence in evolutionary development of the two. Most typically this occurs due to geographic isolation, in which a population is physically split in two. But it’s also little different from what humans do in agricultural breeding, something which Darwin based a great deal of his Origins on. In agriculture, stock is not allowed to freely breed with one another but mates are unnaturally selected, in this case for accentuating features humans find useful in farming, such as increased milk production or muscle mass. This ultimately creates isolated subpopulations who, over time, can appear quite strikingly different from one another.

Saxon Shield,  Red white bar, OC 854 , Steve Ball

A pigeon bred for the tufts at its feet.

Anyways, I digress somewhat. The major point is that scientists have been lulled into a certain way of thinking about feature adaptation ever since Victorian times– as if individual features could be separated from the remainder of the organism in question. But gene knockout and knock-in studies surely have taught us that rarely, if ever, is a single gene’s expression relegated to a single organ. While the timing of its expression may vary, as well as the specific transcripts transcribed, most genes are expressed throughout various tissues and organs of the body. And this is especially the case for genes that are involved in controlling the structure of those tissues and organs.

 

5 responses to “The Absurdity of “Just So Stories” in Explaining Evolution

  1. There’s also a factor [ I owe my awareness of it to Konrad Lorenz, writing in his The Waning of Humaneness (original : Der Abbau des Menschlichen. München (Piper) ]
    that any morphological developments can persist as long as they are not so harmful in their deleterious influences that they actually present a factor which does reduce survival chances. So, any “neutral” development can persist across succeeding generations without presenting any particular advantage–real or imagined.

    However, this might work in non-intuitive ways. For example, I’ve recently speculated that homo sapiens “body odor” might have developed through positive selection. Think a moment about how that might have come about. Numerous mammals do not have any or at least not very extreme body–to our human sense of smell, at any rate. Why not? They might have as “easily” mutated to have this characteristic –but few did develop it. There could be a positive rational for its development in humans–who, notably, reproduce by sexual relations.

    • Very true, it all comes down to survival and reproduction. Although in the case of humans and body odor, since the odor comes from the breakdown of sweat from various microbes, I would think that the odor itself is simply a byproduct of the ability to sweat profusely– something most animals can’t do. (Horses can “sweat” in a sense and quite profusely, but they use the sebaceous gland to do so, creating a lipid-rich lather, whereas humans have a separate sweat gland that produces a liquid that is largely comprised of water.) Although our odor may also have an added bonus of being offputting to certain predators (and other humans! lol).

  2. P:S. : on second thought, we really don’t–and probably can’t–know whether or not other species of mammals have such a feature. Just because it’s not apparent to our senses doesn’t necessarily prove that there is nothing of the kind active among some given species’ members–of course!

  3. My point exactly. If body odor was “a bug” rather than a prized “feature,” then the procedure for its elimination–i.e. general “hygiene”–would or could be regarded as “positively selected.”

    Perhaps, then, Neanderthal was not only a “kinder, gentler, Homo sapiens but he might have smelled better, too, posing a problem for sapiens men in competition for sapiens “womenses.”

    Then Neanderthals would have to be wiped out, as unwelcome competition–what competition _is_ welcome?, come to think of it.

    “Sure, your guy is bigger, stronger and meaner. But my guy smells better!”

    “Hmmmph! Can’t have everything!

    And so were born both female rivalry and the seeds of future feminist debates on the problems of civilizing the recalcitrant male.

    “Igor! It’s bath day! Igor!? Igor!?”

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