Evolution of the Chin

Something I recently read (I now forget what it was) said that it took biologists a long time and a lot of work to figure out that the chin was not specifically selected for.

Anyone know anything about this? How would you figure out that something wasn’t selected for?


I asked a similar question about a year ago; dunno if anything here might help.

I have no idea how they figure out if it was selected for or not. Perhaps they’re simply assuming that it has no function, and therefore wasn’t selected.
Of course, my argument in the thread twickster links to is that it IS selected for – it’s another case of a physical trait being sexually selected for, like colorful male bird plumage, or (and I know someone’s going to squawk at this) female buttock-echoing breasts.

A Family Guy take on the subject.

If nothing else, a strong chin is possibly better for your bone structure and can indicate the absence of certain bone-weakening diseases during childhood, I would think.

If I can recall Physical Anthropology 100, which I probably can’t, it’s not so much as the human chin became prominent but that the size of human teeth decreased, changing the facial proportions.

The chin is your teeth’s first line of defence from being smashed in when you accidentally “face” the wall of your cave.

Yes. The idea is that what was actually selected for was a reduction in tooth size. The reduction of this part of the jaw resulted in the chin becoming more prominent. The chin itself was not selected for.

This general fallacy of providing an adaptionist interpretation for every feature, even when what was actually selected for was something else, was discussed in the classic paper by Stephen J. Gould and Richard Lewontin, The Spandrels of San Marcos and the Panglossian Paradigm.

Colibri, the link to the Gould and Lewontin article is showing me an error message. Is it me or the link?

I fixed the link.

One of my favorite examples along these lines is not the chin but the butt-crack.

We once got a mailbag question asking what is the purpose of the human butt-crack. Of course, the answer is that it is simply the result of the evolution of the buttocks themselves, which developed in order to hold the torso upright when we became bipedal. The butt-crack has no evolutionary purpose in and of itself; it is just the consequence of having buttocks.

Why “This”?