[tsimionescu]

This is not about a genetic, evolutionary change from an underbite/edge-to-edge mastication back to overbite/up-down mastication. The theory is that this happens in individual humans based on their diet growing up: if you were to take a hunter gatherer child and raise them with a modern diet, they would have the modern overbite; and conversely, if you raised your child with a hunter-gatherer diet, they would develop an underbite.

And while the exact cause may be debatable, as is the impact on language, the fact that this change happened over the last few thousand years is established fact, easily visible in human skeletons.

[crazygringo]

> and conversely, if you raised your child with a hunter-gatherer diet, they would develop an underbite.

I.e. an edge-to-edge bite?

I understand this is the idea behind "mewing", but I thought there was no actual evidence for that, and that it is not the consensus scientific position? Or has something changed?

[robbiep]

Not exactly your question, but it is well established that chewing/gnawing as a (young) child is directly proportional to jaw length (I guess you could say prognanthicism to some degree) - but specifically the amount of space available in the mouth for teeth. People who chewed/gnawed on ie a rug or something as a child are less likely to have crowding in their mouth and more likely to have eruption of wisdom teeth without an issue. This makes sense - using your muscles in these ways especially during significant developmental stages changes the release of trophic factors which in turn change development.

Really it’s no different from how someone who uses their body differs from someone who is sedentary all the time but in this case the timing of the ‘intervention’ causes big downstream changes

[quanto]

Indeed. In fact, as a tongue-in-cheek example in real life, you can see the subtle facial structure difference between Asians (say, southern Han Chinese in Fujian) versus 3rd generation Chinese Americans from the same region (with no mixed ancestry). Diet, language, facial muscle behaviors (e.g. frowning), and surrounding beauty standards may have contributed to differences in the mandibular (and elsewhere) structure. Western diet tends to be a bit more chewy and meaty than, say, softer carb-heavy southern Chinese diet.

[metalman]

Hunter gatherer is not a monolithic term, and it is completly obvious that humans have adapted to inumerable diets in countless ecological nieches. We have always been omnivores and semi nomadic and in the vast majority of cases have utilised dramaticaly diffrent food sources, based on seasonal availibility, and chance oportunity. Cant see any plausable reason to make the conection that is bieng made with language.

[tsimionescu]

It's not a monolithic term, but there are commonalities that define it. For example, all hunter gatherers lead at least partly nomadic lifestyles, without any fully permanent settlements (though they can have constructions they gather to, and sometimes spend significant parts of a year at). As such, they won't have, or at least not rely significantly on, things like mills or cutlery. This will mean that, in all climates, hunter gatherers will have a diet that requires much more physical effort to tear off and chew than most agricultural societies, and definitely much more so than any modern diet.