Here's a book review from The Guardian that might be of interest:

Running: A Global History by Thor Gotaas

http://www.guardian.co.uk/books/2010/jan/03/running-long-distance-global-history

I haven't read it yet as I'm vowing to complete more of the many unread books on my shel before spending more money on books, but it looks really interesting. Here's an excerpt from the review by writer Christopher McDougall:

"Gotaas's span begins with prehistory, arguing that because of our sweat glands and springy leg tendons, humans are the greatest distance runners on earth. Our tremendous efficiency at venting heat and maximising caloric energy allows us to run big game to death by chasing them across the savannah until they collapse from heat exhaustion. Access to meat allowed us to grow big brains, while tracking animals allowed us to use this cerebral hardware to develop abstract thinking, verbal communication and cooperation strategies, the mental skills we'd later use to come up with intravascular surgery and iPods."