During the past six million years or so several species of humans have simultaneously inhabited Earth at any one time, but today only one species, ours, remains. How did this come to be? This is the question behind part 3 of the NOVA documentary series “Becoming Human” (see my reviews for parts 1 and 2), and the show does not get off to a strong start.

Though I might be a little more merciful on the producers of this documentary than Greg, he was right to point out that the opening segment of the show is worn old tripe about how our species has fulfilled a kind of evolutionary destiny set in place millions of years ago. The