The August 2004 issue of Behavioral and Brain Sciences has a number of articles
on the evolution of human speech, and the role of food sharing in evolution.
Some of the articles also touch on the topics of bipedalism and encephalization
(among other interesting topics).

Now for the good part: right now the whole issue is available as a free, sample
issue online. The table of contents is at:

http://journals.cambridge.org/bin/bladerunner?REQUNIQ=1117390523&REQSESS=2957183&117000REQEVENT=&REQINT1=276839&REQAUTH=0

Tom Billings