So as I said, in the absence of strong evidence for the multiregional theory I tend to think the "out of Africa fairly recently in one lump" theory is more likely.
Ah, ring species, thanks. I have wondered when the threshold occurs in genetic drift that voids breading between two species that share the same ancestor. I suppose shorter lives, faster reproduction and high mutations help. All that aside, I do think the bottleneck theory does explain why we are similar.
As to why humans aren't a ring species - which could do be due to humans have long lives, longer reproduction cycles, low mutation rate (the opposite being bacteria!) - it's a good question. But not one that discounts the theory of there being mutations. There are plenty of mutations between human races: height, color, fast/slow muscle twitch, somatotype, skin colour ... so on this basis I find it difficult to believe that there isn't a difference overall between races on mental makes up. And this isn't just about IQ & EQ, I also think there is variation between: memory, spiritual feelings, mental diseases. It's pretty difficult to back up these statements without proper data, and I doubt there will be any since I bet many senior respected scientists don't want to be associated with racism.
I said some of the harshest deserts on Earth. IOW, bloody hot and dry climates with extremely limited resources. These climates can be lethal very quickly.
Hmm. I think some perspective is needed here. Humans will die in the most extreme conditions. Hot or cold. But take the moderate range where humans will move to in order to harvest, live and hunt animals, and it will be slightly less extreme both ends. So lets have two ranges, -5 - 25 degrees and 15-35 degrees. In a warmer climate there is less energy loss, that's why cold blooded animals and insects thrive. In colder climates to keep warm more energy/biomass is needed, even gained before the lowest temperatures of the winter.
Hominid brains were increasing in size before any of them left Africa so it aint all down to hunting mammoths in Asia.
It could be due to developing a language. It could be due to killing of Neanderthals. I still think cold climate is most viable options of the lot.
As to nutrition needed for a growing brain, the latest articles I've read on is the power of Omega 3 in oily fish leading to human brain development. I think to some extent this is true, some studies have shown it improves concentration, and the Japanese love fish, and even eating it while it is still alive.
Topic: High IQ turns academics into atheists