@fresco,
Yeah, I'm aware of Harris' argument, but I'm not convinced. Religious people have produced a great deal scientific, humanitarian and medical advances, also. Harris seems to be a bit one-sided in selecting a negative and saying it outweighs all the positives.
I agree with the innate tribalism view, but I'm not sure it's sufficient to explain how even in times of plenty, leaders exhort their citizenry to aggression against others. That's not a matter of survival, it's often a matter of greed, sometimes revenge (anger), sometimes fear of the unknown foreign element. When North Korea attacked the South in 1950, the North was economically ahead of the South. They wanted more and found an
ad hoc justification for the attack in their communist, revolutionary ideology.
My list (greed, fear, anger) isn't meant to be exhaustive, by the way. Just pointing out that what is so often put down as a religious justification for inhumane acts can usually be more accurately interpreted in terms of more fundamental drives. Not making a blanket statement about it, though. There are almost always exceptions.