I thought that it was the use of tools or the invention of them, that reduced the need for mankind to have larger jaws. Raw meat would be far tougher to chew, which would result in having to develop larger muscles in the jaw in order to swallow food. Tools would reduce the need to chew excessively. How would this equate to a genetic mutation? Can it also be said that earlier men genetically mutated into weaker humans because of transportation? Instead of walking 500 miles, we can now sit on our cans and enjoy the scenery. My point is that earlier men were hardier than modern men due to lack of luxuries. Just a thought.