Aside from a few courses in college, I'm no professor of anthropology or sociology, so I can't say for certain how the stages or steps in human evolution contributed to any particular current human behavior or emotional attribute. But, if I had to guess, I'd think that the way our ancient ancestors survived on this planet says a lot for how we react to things today.
One of those habits frustrates me more than others, because it's a tough one for me to break! It's that immediate clenching onto something good, that desire to protect, hide, miser or hoard what you're blessed with, mainly for fear of running out, not having enough or having it taken away.
I caught myself having that reaction just recently, and after I realized it was causing me more anxiety than it was comfort, I remembered something I'd heard a very wise lady speak about once. She said that the fear of not having enough means that we often hold things too tightly and don't want to share. She was so right, and we all do it because we're taught to "watch our backs" and "look out for number one" and proceed with caution and distrust. Now, don't worry that I'm dense enough to think everyone has my best interests at heart -- HA! But, I'm pretty convinced you win more people over, inspire more good-will through generosity and kindness than by taking a clique-ish or starving-squirrel-hoarding-away-nuts approach. And Lord help me, I have to constantly remind myself not to fear being screwed over. I was raised with a starving-squirrel-hoarding-away-nuts mentality, but all it really does is give you ulcers, right?
What if people tried reacting the exact opposite way of that instinct, the negative tug in the gut that makes you grab onto something and say, "mine!", even if you're only saying it in your head. In fact, especially if you're saying it in your head, because that psychological tape-recorder needs re-recording. Practice makes perfect, so I'm just going to keep trying to give it away. *Smirk* Yeah, yeah, I know what I typed, you dirty birds.