Twisted Tree of Life Award: NPR on the Evolution of Crying

Well, normally I really like NPR science stories. But this one dug into my anti adaptationism feelings. Adaptationism is, in essence, the practice of saying something must be adaptive (i.e., beneficial), simply because it is there in an organism. Such cases are also referred to as “just so stories” – a play on the old Kipling “Just So Stories“.  That is, in essence, people who claim something is adaptive just because it is there are in essence telling you something is this way because it is just so.   I am actually not sure of the whole history of using the just-so analogy to refer to adaptationist stories – I know Stephen Jay Gould discussed this a lot in his books and lectures, but not sure who first did it. 
Anyway – NPR has an adaptationistic doozy from Morning Edition: 

Teary-Eyed Evolution: Crying Serves A Purpose : NPR

Basically, it seems the gist of the argument here is the following line:

Scientists who study evolution say crying probably conferred some benefit and did something to advance our species — because it’s stayed with us.

Wow – that is like straight out of the adaptationist playbook.  The problem with this argument is that many things exist and persist in organisms even when they are not adaptive.  There are many reasons why this can happen from constraints (e.g., if bones were not adaptive in humans it would be pretty hard to get rid of them) to  invisibility to selection (e.g., some features that only show up after reproductive age may not really influence fitness) and so on.

In essence the NPR story is one of the worst examples of adaptationism in the good science press I have seen in a while.  Sure this shows up all over the place.  But rarely this bad at NPR.  The story ends with an even worse line than the rest

Maybe that’s another reason evolution kept humans weeping: Tears help reveal the truth. And that’s because along with the tears, we’ve evolved a very sophisticated ability to interpret them.

Yes that is right.  Crying has been maintained in humans because we also evolved another adaptive feature – the ability to interpret tears.  So the logic here is that crying is adaptive because it is needed for another adaptive trait for which there is no evidence it is adaptive.

So for their story on crying and for in essence inventing some just so stories to explain why they think it is adaptive, NPR is the recipient of my Twisted Tree of Life Award.  Previous recipients are

See also these things for some stuff on evolution of crying:

About Jonathan Eisen

I am an evolutionary biologist and a Professor at U. C. Davis. (see my lab site here). My research focuses on the origin of novelty (how new processes and functions originate). To study this I focus on sequencing and analyzing genomes of organisms, especially microbes and using phylogenomic analysis

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