Another problem of averaging under convexity. Traditionally we have had *on average* slightly more than 2 children per woman (net of child mortality), which is the rate people converge to today. Except that in the past ~2 out of 10 children survived, today 2 out of 2. It means that we no longer have selection at work, since survival was not random. And, further, there was a high variance between women: some had no surviving children, others had many (for the same overall average).

So, clearly the world today is better, fairer, with equal opportunity to survive and be survived. But we cannot compare evolutionary processes to those of the past.

via Another problem of averaging under… – Nassim Nicholas Taleb.