What's it for?

I learn this week that a large amount of effort has been put into the question of the beetle-brows of our ancestors, in particular the beetle-brows of a chap called Kabwe 1 of the clan homo heidelbergensis – with Kabwe being a place in Zambia and Heidelberg being a place in Germany. Why did he have such big brows and why do we not have such brows?

My first thought was does such a feature have to be for anything, can it not just be some sort of accidental by-product, an engineering left-over? To which the answer may be that such a large feature consumes much energy in its construction, energy which could be put to better use, and over a long time, evolution will tend to iron out such waste.

So my second thought was that perhaps heavy brows served to provide protection for the eyes, not at that time (some hundreds of thousands of years ago) protected by our high forehead. They could also be used for head butting, after the fashion of rampart rams and billy-goats. A feature of the social and sexual life of certain ruminants.

Some more learned opinion went for skull reinforcement to support a massive bite, tending towards the massive bites of modern carnivores. Other learned opinion went for filler, smoothing over the otherwise awkward junction between the eyes front and the brain back.

While the paper which got me going (reference 1), appears to be suggesting that whatever the beetle-brows were for, they were traded in for expressive eyebrows. Highly mobile eyebrows which were friendly rather than aggressive and which were an important part of turning us into the social animals which were able to become what we are now. Cooperation won out over competition.

Perhaps the Tories, always keen to puff the importance of competition, should read a bit of history.

With thanks to Professor Paul O’Higgins of the University of York, for his snap of an old skull in front of a new skull, illustrating the coming and going of the brows in question.

PS: no access to my trusty OED at the moment, but there was a suggestion in one of the various online dictionaries that the ‘beetle’ part of the old phrase ‘beetle-browed’ may have been derived from the facial features of a certain kind of beetle.

References

Reference 1: Supraorbital morphology and social dynamics in human evolution - Ricardo Miguel Godinho, Penny Spikins & Paul O’Higgins – 2018. Not open access, but Google turns up plenty of coverage in the specialist press.

Reference 2: https://en.wikipedia.org/wiki/Homo_heidelbergensis.

Reference 3: Browridge development in Cercopithecidae—a test of 2 models - Ravosa, M. J. – 1988. An example of earlier work in this area. I was defeated by the abstract.