[Retric]

Evolution has a long history and vestigial adaptations don't instantly disappear if they are part of complex systems. Rat brains also use dopamine and there seems to be a link between dopamine and depression so it's roots might be vary ancient.

Looking modern males at the average American high school, biker gang, or hunting party and you will notice social stratification. Humans don't do the Alpha with harem, but young men often fight for levels of dominance. In scripted environments they might fight over academic prowess but simple fist fighting is not that uncommon. And when males fight you get into some basic game theory as to how much energy to expend and damage to risk.

If the systems that cause depression where useful thought human history then removing the possibility of depression may have had serious costs.

PS: Just because the human brain works extremely well does not mean it's elegant.

Edit: Modern hunter gathers have just as much history as we do. Extrapolating how humans lived 500,000 years ago from what we have seen modern bands do is a mistake.

[kingkongrevenge]

There were no humans 500,000 years ago. Fully modern humans are more like 60,000 years old. And truly cognitively modern humans are more recent than that.

> Looking modern males at the average American high school, biker gang, or hunting party

Well, I say you watch too many B movies. Struggling for social dominance in a hunting party? Really? Nobody fought for "dominance" at any social institution I've been involved with. However, people do all kinds of weird things, much like zoo animals, when caged in unnatural environments like public schools, housing projects, corporate cube farms, and prisons.

[Retric]

There were no humans 500,000 years ago. "The term "human", in the context of human evolution, refers to the genus Homo," "The Homo genus diverged from the Australopithecines about 2 million years ago in Africa."

http://en.wikipedia.org/wiki/Human_evolution granted Homo sapiens are younger than that.

Nobody fought for "dominance" at any social institution I've been involved with. I recall doing this on several occasions in unscripted environments. I don't know if you are male, or if you spent much time unsupervised with groups of 8 - 20 other young men, but it's seemed really common.

This might also be more obvious to those who win these games. And there are edge cases. I recall having 12 people watching me play video games and when my mother asked me to share I offered and got a “we just want to watch” response. This seemed more like a completion to find the best followed by watching the master situation. But it was still odd and even though the observer never saw the dominance play it still happened and if I was less talented we would have kept sharing for longer.

I also recall being a member of a crowd watching the master at an arcade even if nobody watches game play videos. It's also customary to have the person who wins keep the table in pool or fighting games. This is normally less obvious than simply beatings ones chest, but watch how people walk around a body builder some time.