This is a very interesting "chicken and egg" proposition. Sweating seems to have been accompanied by the loss of body hair, both to facilitate heat loss. Hunters on the African savannah are thought to have employed lengthy chase strategies on ungulates who could not easily regulate body temps and must stop to cool off after less than an hour of running. It seems likely that there was parallel adaptation, with our cooling capabilities allowing us to utilize more nutrient dense food sources which were in turn necessary to fuel an increasingly large brain, which was cooled by our increased cooling capabilities.) I'll have to search out the book, nice write up! BTW, I clap in base 12, it's a nerd thing;)