Love your blog!. So many science blogs are tied down with science vs religion. I want more science! I would think another way to avoid Malthusian crises is migration. The idea of a better life over the next ridge is a major human compulsion. Certainly hasn't stopped in today's world despite major attempts to limit it. Of course, brilliant graduate students are welcome but poor peasants are not.
Thanks so much for the kind words!
True enough, although migration is only a temporary out. My own thinking is that these ancient populations were locked in a source-sink dynamic. Some places were good to live, at least for most of the time, and produced excess people who migrated elsewhere. But the rest of the human range was not-so-good to live, and people there were constantly reproducing below replacement. So they absorbed migrants who were, in the long-term sense, doomed.
So in that sense, I think migration is the most important way to deal with density-dependence for these ancient people. But from the genetic point of view, it may not have really been better than staying and fighting it out – except that might have degraded the local ecology in a way that turned a relative source into a sink!