a larger group will split when it gets too big for an area
Say there are two kinds of forager groups, one which limits reproduction of its members by various means, and another that does not limit reproduction and instead constantly grows and splits and invades other groups' territories if needed. Naively I would expect that the latter kind of group would tend to drive the former kind out of existence. Why didn't this happen?
From Mike Darwn's Chronopause, an essay titled "Would You Like Another Plate of This?", discussing people's attitudes to life:
Conclusion, graphs, and references in article. As usual, I recommend reading Chronopause.com as Darwin has many good articles; to quickly link a few: