Altruism, the much revered behavior we all idealize but often brush off as impractical seems to have originated from our distant nomadic history than from our recent civilized past! The fact that we emotionally crave for it emphasizes its evolutionary significance.

I believe this behavioral trait had a significant survival impact for our nomadic hunter-gatherer ancestors. We, humans, lived as hunter-gatherers for a good part of our existence (200,000 BP to 50,000 BP) and were predominantly egalitarian and altruistic. Why did our ancestors depart so abruptly from their reptilian past and adopt an altruistic stand?

The answer probably lies in the proto-economy of exchanging favors that flourished in that era and the fact that such economy required an individual to be altruistic / just to participate. Our ancestors could store little for their future needs and any excess (meat, hides or tools) was a burden to carry through their nomadic existence. The only viable option was to give them away as favors and redeem those favors when required. This abstract culture of exchanging favors should have conferred a significant survival advantage to those who adopted an altruistic stand and could have preemptively excluded opportunistic participants to sustain and flourish!

Finally, evolution of agriculture and trade could have eroded the value of Altruism as civilization moved forward!