Any mention of "alpha male" costs you your entrance ticket to the discussion. There is no such thing in humans.

> An aggressive alpha male can kill you

What advantage does an "agressive alpha" have over you? Any human can kill any other human very easily. Rock to the head, game over. We're not talking about walruses.

Social power structures of any complexity are a post-agricultural development, and therefore of limited importance to human genes. The social structure in a hunter-gather band of 20 is simple and flat.

As trite and cliche as mentions of "alpha male" have become, there is good reason to believe that early human social structure might have involved just such a character. Namely, some of our closest relatives in the great ape family have this sort of "alpha-male-with-harem" approach.

Now, there is also good reason to believe that the evolutionary adaptation that pole-vaulted early humans ahead of the other apes was a change in their social structure. However, even if that is true, you also have to remember that humans have spent a much larger portion of their evolutionary lineage as great apes than as modern (or nearly-modern) humans. That is, even if early humans had distinct social structures from their ape cousins, we are bound to have many remnants of the ape social structure left in our genomes.

In other words, depression doesn't necessarily have to have been an adaptation of early humans, it could just as easily have been an adaptation of early primates that humans just haven't had time to get rid of yet!

If you accept the popular premise that man is a pleistocene animal designed to live in hunter-gatherer bands then you don't really have to wonder much about the innate social tendencies of humans. We have dozens of detailed ethnographies of hunter-gatherer bands. They are socially flat. Some people are highly esteemed, but nobody has any sort of disproportionate power.

> the ape social structure left in our genomes

The apes and the gibbons vary dramatically so it seems a bit silly to expect useful common denominator social behaviors applicable to humans. Bonobos and gorillas and orangutans are all very different. And none of the apes are at all comparable to humans in how they make their living. None of them are primarily team hunters.

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.

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.

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.

Considering the biologist in this thread disagrees with you, you may want to tone down your arrogance.

Also, I do not think you could kill me with a rock, unless I were sleeping and you were dropping it from excessive height.

I see no disagreement.

I could kill you with a coffee mug or a bic pen if you were unarmed. In the unlikely event you're unusually strong and alert I'd get my brother to help. Power in a band of humans has way more to do with how many relatives you happen to have than any silly conception of "alpha".

So, maybe the 'alpha' is automatically the person with the most allies in a time of conflict.