war seems to be part of an evolutionary algorithm to select the best species or feature set and prune the legacy code, and then diversify again and prune again at a higher level.

The individuals being selected are only the "best" if you value killing over everything else. If you, for example, value preservation of genetic material then war selects some of the worst people.

What about tacticians, logistical support personal, medical staff, etc?

I think there's a lot of jobs that war would select for that don't involve killing. Early man interested in treating wounds would study the human body and try to repair it, as one example. These valuable and intelligent humans would be promoted just like today's .mil and be more likely to procreate.

I think it's more that aggression and the instinct to protect ourselves are part of all DNA. We only have to look at ants being invaded by a foreign species to see that.

Also, since everything is based on the bell curve, out of 7 billion people, there will be people who are born with the perfect storm of personality traits to start a war, and with the right (or wrong, more accurately) life experiences will start that war. Hitler was a perfect example. Statistically it has to happen.

And we are only aggressive because, socially, we are barely out of the trees. We have the ability to blow the world up many times over, yet are consumed by petty intolerance. Our social intelligence lags our technical intelligence considerably. This is the most dangerous time in any civilisations time.

It's funny how few people want to talk about that.

Well, that's the game, though one can argue if you move beyond it you've won by definition. Just because we came from that system doesn't mean it needs to continue.

The losing end of the great filter no one sees coming: peace.

Are you listening cstross? It is time to write a novel about the evils of peace among the spacefaring. Service guarantees citizenship!