Step one is establishing whether or not chewier foods, in fact, do promote jaw growth. It could be that hunter gatherers develop differently for a number of reasons (you mentioned some possibilities), or it could be the case that selection pressures on people with a long history of ancestors living in more developed civilizations have a history of weaker selection pressures on jaw development (or even competing pressures that lead to smaller jaws for some reason, as is the trend in human evolution compared to other primates).
Michael Keenan on Twitter points to an 2012 Wikipedia edit of his (see current version). There’s some studies on association between chewy food and jaw size in animals and one 1987 study about chewing gum in children.
Other things can play a role still! Like whatever movements made it less likely for breastfed children to have underdeveloped jaws.
Step one is establishing whether or not chewier foods, in fact, do promote jaw growth. It could be that hunter gatherers develop differently for a number of reasons (you mentioned some possibilities), or it could be the case that selection pressures on people with a long history of ancestors living in more developed civilizations have a history of weaker selection pressures on jaw development (or even competing pressures that lead to smaller jaws for some reason, as is the trend in human evolution compared to other primates).
But I like the idea!
Michael Keenan on Twitter points to an 2012 Wikipedia edit of his (see current version). There’s some studies on association between chewy food and jaw size in animals and one 1987 study about chewing gum in children.
Other things can play a role still! Like whatever movements made it less likely for breastfed children to have underdeveloped jaws.