I don't think 500 miles would be too far to walk for some sex, especially if there was none available nearby.
Also consider that the population would not be evenly distributed throughout the range, they would not be living on the slopes of the Himalayas for example and they would also probably congregate at resources such as water and stone for tool making.
Kick it around and if you are ever in the mood, try and disprove the Out of Africa hypothesis. If it's a sound hypothesis, it will stand up to the abuse. I have not always been a devotee of the MRH, I only began to take a look at it about 10 years ago.
I also wonder sometimes at my sanity, yelling at a TV screen is a bad thing sometimes. But I didn't feel so bad after Boone hit that homer and my neighbor was really raising hell. His voice really carries sometimes.
------------------
Bringer of fire, trickster, teacher.