re: #15 silverdolphin

This also provides good background comparing humans, chimps and bonobos:

Survival of the Friendliest: Homo sapiens Evolved via Selection for Prosociality, Annual Review of Psychology
Vol. 68:155-186 (Volume publication date January 2017)
First published online as a Review in Advance on October 12, 2016
doi.org

I’m very pleased my comment a few threads down, an idea I’ve been chewing on awhile and finally posted, sparked this interesting discussion!