Aggression is one of the less useful terms here and really deserves tabooing, because it is a too broad term, it covers everything from a bit too intense status competition to completely mindless destructivity.

In other words, aggression is not a useful term because it describes behavior largely from the angle of the victim or a peaceful bystander, and does not really predict what the perpetrator really wants. Few people ever simply want to be aggressive. They usually want something else through aggressive behavior.

I would prefer to use terms like competitiveness, dominance and status, they are far more accurate, they describe what people really want. For example, you can see war between tribes and nations as a particularly destructive way to compete for dominance and status, while trade wars and the World Cup being a milder form of competing for status and dominance. This actually predicts human behavior - instead of a concept like aggression which sounds a lot like mindless destructivity, it predicts how men behaved in wars i.e. seeking "glory" and similar status-related concerns.

This formulating is actually far more predictive of what people want and here the link with testosterone is clear, even so much that researchers use T levels as a marker of a compeititive, status-driven behavior, for example when they wanted to test the effects of stereotype threat in women, they had this hypothesis that being told that boys are better at math will only hold back women who have a competitive spirit i.e. want to out-do boys and will not harm women who simply want to be good at it but not comparatively better than others, they used T levels as a marker of such spirit. They say " given that baseline testosterone levels have been shown to be related to status-relevant concerns and behavior in both humans and other animals".

This is the central idea, aggression is not really a good way to formulate it. To see war-waging esp. tribal raids and other typically, classically male behavior as aggressive, while technically correct, it misses the real motivation i..e. competing for status and dominance.