Cooperate (extra)

While many have considered human cooperation primarily a learned behavior, recent evidence suggests that it may also have biological root.
In a brain-scanning experiment, some scientists found that when humans cooperated with each other, their brains lit up in the same neighborhoods that come to life when we win a prize, or eat a piece of chocolate cake - the inner reward circuitry that responds to dopamine and provides that glow of pleasure.
In other words, we cooperate because it makes us feel good.
And that may mean, some researchers speculate, that the urge to cooperate is, at some level, simply innate in humans.
Perhaps our early ancestors needed to help each other to hunt big game, find more nutritious food, or raise smarter kids.
The ones who successfully learned to work as a team might have had a survival advantage.