Beards and spandrels

One of the least important ways in which the current world-wide crisis over covid-19 is going to affect many of us is the state it is going to leave our hair in. Barbers and hairdressers are closed or closing – either under orders, because custom has dried up or because concerns about staff and customer safety are forcing the decision.

Working remotely – if you are lucky enough to have work – means that personal grooming isn’t quite as important as before (hygiene, of course, is more important than ever).

So this week I didn’t shave for five days – perhaps the longest time as an adult. As a result I grew a decent amount of fur (most of it white, I’m afraid) and when I shaved it off I was set to wondering why the different bristles on different parts of the face, while generally of a similar length, were of different stiffness.

On the cheeks the hairs were softer (and all white too). While on the chin they were stiffer and on the upper lip very stiff indeed (and also dark).

I mused publicly on what selection criteria had created this:

And sure enough a biologist – my friend (Dr.) Tim Waters replied and questioned whether why I thought it might be an evolutionary adaptation at all, and referred me to this paper – The Spandrels of San Marco and the Panglossian Paradigm: A Critique of the Adaptationist Programme. If you have half an hour or a bit more to spare I really recommend it – there are a few terms in there with which I wasn’t familiar but the core argument is very accessible and the paper is brilliantly written.

Its core metaphor is of the spandrel – the triangle created by placing an arch below a straight line (or an upside-down arch above a line). The authors (Gould and Lewontin) suggest that far too many evolutionary biologists would treat what ever was used to fill the triangle as having been selected for evolutionary advantage when, actually, it’s just a by-product of a bigger selection decision (eg., to have a dome resting upon arches).

The evolutionary-adapation-above-all idea is firmly embedded in public consciousness – in large part thanks to the brilliant popularisations by Richard Dawkins – but Gould and Lewontin cut through a lot of that like a knife through butter. I’m not qualified to make a judgement on who is right here, but it’s a fascinating debate.