For me, one of the most interesting books of the 70's was Elaine Morgan's work ' The Descent of Woman'.
In it , she argues that humans became the shape , and the species we are today because we spent a lot of time in an aquatic environment. she also argues that it was our child rearing habits, rather that our hunting skills that made us 'human'.
'Forget "Man the Hunter" as an explanation for our big brains and language skills and all the other stuff that makes us interesting. Look instead at " Woman the Home maker" ' she argues, everything from our courtship rituals to our political systems can be traced to our behaviour as primates.
I have to confess that I find her very persuasive, and think her book is brilliant. I love her theories, her style of prose, her sense of humour and wonder if anyone else has read the book and has anything to say on it...