[AndrewC]

It is possible for individuals to benefit a population without reproducing.

Agressive individuals can make good soldiers and benefit their community, even if they die before reproducing.

But the trait dies with the individuals and is not passed on. Therefore, you will not have aggressive individuals except by accident.

[js1138]

But the trait dies with the individuals and is not passed on.

Nonsense. recessive and multivariate genes do not die when individuals die. Their frequency in a population depends on their usefulness to the population.