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Let's play find-the-spandrel!

Let’s play find-the-spandrel!

We just passed the 35th anniversary of the publication of Gould and Lewontin’s classic, highly cited, highly controversial essay (diatribe?), “The spandrels of San Marco and the Panglossian paradigm: a critique of the adaptationist programme.” The 21st of September 1979 was the fateful date. Every PhD student in biology should read it (you can find pdfs here— this post assumes some familiarity with it!) and wrestle with it and either love it or hate it- THERE CAN BE NO MIDDLE GROUND! With some 5405 citations according to Google Scholar, it has generated some discussion, to put it lightly. Evolutionary physiologists and behaviourists who were working at the time it came out have told me stories of how it sent (and continues to send) shockwaves through the community. Shockwaves of “oh crap I should have known better” and “Hell yeah man” and “F@$£ you Steve,” more or less.

I am among those who love “The Spandrels Paper“. I love it despite its many flaws that people have pointed out to seemingly no end- the inaccurate architectural spandrel analogy, the Gouldian discursive (overly parenthetical [I’m a recovering victim of reading too much Gould as an undergrad]) writing style, the perhaps excessive usage of “Look at some classic non-scientific literature I can quote”, the straw men and so on. I won’t belabour those; again your favourite literature search engine can be your guide through that dense bibliography of critiques. I love it because it is so daringly iconoclastic, and because I think it is still an accurate criticism of what a LOT of scientists who do research overlapping with evolutionary biology (that is, much of biology itself) do.

The aspects of The Spandrels Paper that I still think about the most are:

(1) scientists seldom test hypotheses of adaptation; they are quick to label something that is useful to an animal as an adaptation and then move on after rhapsodizing about how cool of an adaptation it is; and

(2) thus alternatives to adaptation, which might be very exciting topics to study in their own right, get less attention or none.

True for #2, evo-devo has flourished by raising the flag of constraint (genetic/developmental/other factors that prevent evolution from going in a certain direction, or even accelerate it in less random directions). That’s good, and there are other examples (genetic drift, we’ve heard about that sometimes), but option #1 still often tends to be the course researchers take. To some degree, labelling something as an adaptation is used as hype, to make it more exciting, I think, in plenty of instances.

Truth be told, much as Gould and Lewontin admitted in their 1979 paper and later ones, natural selection surely forges lineages that have loads of adaptations (even in the strictest sense of the word), and a lot of useful traits of organisms are thus indeed adaptations by any stripe. But the tendency seems to be to assume that this presumptive commonality of adaptations means that we are justified to quickly label traits as adaptations.

Or maybe some researchers just don’t care about rigorous tests of adaptation as they’re keen to do other things. Standards vary. What I wanted to raise in this post is how I tend to think about adaptation:

I think adaptations are totally cool products of evolution that we should be joyous to imagine, document, test and discover. But that means they should be Special. Precious. A cause for celebration, to carefully document by scientific criteria that something is an adaptation in the strictest sense, and not a plesiomorphy/exaptation (i.e. an adaptation at a different level in the evolutionary hierarchy; or an old one put to new uses), spandrel/byproduct, or other alternatives to adaptation-for-current-biological-role.

But that special-ness means testing a hypothesis of adaptation is hard. As many authors waving the flag of The Modern Comparative Method (TMCM) have contended, sciencing truth-to-adaptationist-power by the rules of TMCM takes a lot of work! George Lauder’s 1996 commentary in the great Adaptation book (pdf of the chapter here) outlined a lengthy procedure of  “The Argument from Design“; i.e., testing adaptation hypotheses. At its strictest implementation it could take a career (biomechanics experiments, field studies, fitness measurements, heritability studies, etc.) to test for one adaptation.

Who has time for all that?

The latter question seems maladaptive, placing cart and horse bass-ackwards. If one agrees that adaptations are Special, then one should be patient in testing them. Within the constraints of the practical, to some degree, and different fields would be forced to have different comfort levels of hypothesis testing (e.g. with fossils you can’t ever measure fitness or other components of adaptation directly; that does not mean that we cannot indirectly test for adaptations– with the vast time spans available, one would expect palaeo could do a very good job of it, actually!).

I find that, in my spheres of research, biomechanists in particular tend to be fast to call things they study adaptations, and plenty of palaeontologists do too. I feel like over-usage of the label “adaptation” cheapens the concept, making the discovery of one of the most revered and crucial concepts in all of evolutionary biology seem cheapened and trite. Things that are so easy to discover don’t seem as precious. When everything is awesome, nothing is…

I’ve always hesitated, thanks in part to The Spandrels Paper’s indoctrination, from calling features of animals adaptations, especially in my main research. I nominally do study major ?adaptations? such as terrestrial locomotion at giant body sizes, or the evolution of dinosaurian bipedalism. I searched through my ~80 serious scientific papers lately and found about 50 mentions of “adapt” in an adaptationist, evolutionary context. That’s not much considering how vital the concept is (or I think it is) to my research, but it’s still some mentions that slipped through, most of them cautiously considered– but plenty more times I very deliberately avoided using the term. So I’m no model of best practice, and perhaps I’m too wedded to semantics and pedantry on this issue, but I still find it interesting to think about, and I’ve gradually been headed in the direction of aspect #2 (above in bold) in my research, looking more and more for alternative hypotheses to adaptation that can be tested.

I like talking about The Spandrels Paper and I like some of the criticism of it- that’s healthy. It’s a fun paper to argue about and maybe we should move on, but I still come back to it and wonder how much of the resistance to its core points is truly scientific. I’m entering into teaching time, and I always teach my undergrads a few nuggets of The Spandrels Paper to get them thinking about what lies beyond adaptation in organismal design.

 What do other scientists think? What does adaptation mean (in terms of standards required to test it) to you? I’m curious how much personal/disciplinary standards vary. How much should they?

For the non-scientists, try this on for size: when our beloved Sir David Attenborough (or any science communicator) speaks in a nature documentary about how the otter is “perfectly adapted” to swim after prey underwater, do you buy into that or question it? Should you? (I get documentaries pushing me *all the time* to make statements like this, with a nudge and a wink when I resist) Aren’t scientists funny creatures anyway?

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