How did human intelligence arise “so suddenly”?
We do not know how many genes had to change to go from a level of intelligence typical of other living great apes to that found in humans. Thus, it is very difficult to assess whether the rise of human intelligence was especially fast. There is reason to think that selection for brains that could learn complex tasks quickly could be very strong. Thus the real question is how come there was sufficient genetic variation for selection to act upon. But, again, the lack of genetic data make this hard to answer.
