How the sieve changed the skull (or not)

16-Jun-2017

***Correction to this information - see bottom of blog***

 

Of all the nightmare fodder I shared on the last post, the question that came through the comments was about how food has changed skull shapes. Well, what can I say but that I am happy to help?

 

Using my handy copy of Simon Mays' The Archaeology of Human Bones (pp,96-100) and the Colour Atlas of Human Anatomy  (pp.14, 70) and a bit of a search on the web (as unfortunately the main references from Mays are behind paywalls), but with this handy paper by Rock, Sabieha and Evans, and a bit of thinking, I can give you this quick summary.

 

Since neolithic times, we've been making life easier by making our food softer. Wolff's law says that bone tissue tends to build up where it is needed, and can be lost in areas where it is not. This can also impact shape as well as size of bones when being regularly worked. I could go into the technical language of the relationship of the maxilla to the anterior cranial fossa... but if you want that - you're already studying archaeology and reading the papers, and don't need my amateur pictures.

 

So instead I'll put it in language for the layman (like me) (layperson?)

 

tough food = big chewing muscles

Big chewing muscles + squishy skull bones = skull flatter along top and squishes out at back

Since we invented various things to be kind to our teeth, like cooking, cutting and grinding our food in preparation, we have much weaker temporis muscles.

 

(Major aside... the temporis muscle fits under your cheekbone and shows at that bit in your temples that bulges when you clench your jaw. Some actors show anger by clenching their jaw - and you can see the temple pulsing. I wonder if that also uses the masseter?  The masseter goes over the cheek to attach to the bottom of the jaw on the ramus. That could mean a flared ramus indicates heavy chewing or having a temper in children? Note to self - check Robert Redford's biography. But I do like the look of a nice flared ramus. And now I search for it, I find people do cosmetic surgery for that. How messed up is that?  I'll never trust a flared ramus then.)

 

Interestingly, there is a whole centimeter of skull height gained in the last 500 years - apparently due to sieving flour and moving away from bran and rye breads (take that, bread hippies!). This could go further with a vegetarian diet - e.g. mine was somewhat driven by how bored I got chewing my way through grey school meat as a child, and that I rarely even try eating meat now as my jaws ache so much from all that unnecessary chewing! I imagine my temporis muscle is the size of a standard post office elastic band.

 

Personally I then wondered what bit of our modern brain might now have more room to grow, so here's some brains too.

 

Modern skulls, with their increased cranial height happen to be the areas of problem solving, concentration, planning and motor control. Which is nice.

 

It might squash the areas of co-ordination and vision though. Which is less nice.

 

Some people have speculated that skull binding to deform the cranial case might have had effects on brain function (O'Brien, Peters and Hines) like memory and motor function. And this would be less extreme, but similar.

 

However, this may have no effect at all because of neuroplasticity. Without good experiments with sensible controls, it is hard to know. (So do write in if you have twins and are happy to try skull binding one of them to see how it affects their school performance.)  

 

But, when you've got your eye in a bit for 'typical' skull shapes (though individuals vary more than the trend), it can help give a feel for dating it. Have a go on the example male skulls below - one if a medieval skull (before the fine sieves), and one from the Victorian* era, both of European origin.

 

*Of course there is also the big tip off of the medical skull cap removal on the Victorian skull.

 

***Correction to this information*** I've been alerted to some problems with the paper I used.

Sent to me by my friendly skull expert extraordinaire

 

"FIRST, the skulls they used are all ‘modern’ in terms of what food people would be eating. Food had been cooked, and in fact meat often cooked into almost oblivion in the endless stews and pottages of the poor, since at least the Neolithic. Meat was never chewy, except by accident. Yes, there would have been more stone-ground cereals pre-late 19th century, but we eat those again now and they don’t require any more intense chewing (although they do, of course, rasp away tooth enamel). For a comparison to be valid, it would have had to compare modern humans with earlier hominid ancestors, and this has been done and shows that we are gradually losing our ‘muzzles’, almost certainly because we are depending less and less on our sense of smell (many parallels in other mammals, especially primates). This reduction in muzzle also means that there is less room for third molars, are we are losing them, or suffering from them getting impacted.

 

AND, modern human skulls vary in shape due to genetic factors, which is why it is possible to work out ethnicity based on skull shape. So, as people come into England, they bring their genes for skull shape with them, and this could have led to the apparent pattern that the researchers found."

 

So, for my simple minded summary, I'm now enjoying the image of our reducing muzzle size. Imagine the transformation from the American Werewolf in London, but in reverse. (Yes, at this point, I'm not going to attempt scientific rigour.)

 

 

+Also the Temporis muscle should be the Temporalis. Damn brain fog.

 

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