Have you considered that the body may produce different hormone levels as a result of our mental state?
For example, when startled, the body produces a hormone called adrenaline. We know with certainty that mental state is responsible for certain types of hormone production.
I honestly do not know if there might be a link between testosterone production specifically and mental state, but I took this to be the question that the above poster was asking.
https://www.webmd.com/men/features/exercise-and-testosterone
Lower testosterone causes fat gain and fat gain causes lower testosterone.
https://simondsmetabolics.com/2020/09/10/how-obesity-affects...
> Scientists have established that excess fat increases enzymes known as aromatases. These molecules convert testosterone into estrogen. While estrogen is present in males in very small amounts, increased amounts can alter normal function. Having too much estrogen tricks the body into thinking that you do not need more testosterone. The danger lies in the vicious cycle that develops once the high estrogen levels kick in.
Cheap, high calorie food and obesity...
I was actually considering something like that. That if you engage in more aggressive behavior regularly for a long period of time, your testosterone levels might stay higher on average than if you didn't.
You seem to assume testosterone levels are only a function of genetics, which they are not.
How exactly do you propose that a change in socially acceptable behavior in the span of about 40 years had a tangible effect on hormone levels? It's not like someone can say "oh getting into fistfights isn't cool anymore, better reduce my testosterone levels". Maybe if we were talking about a timespan an order of magnitude or two longer then sexual selection (high testosterone and more violent men being less favored as mates) could come into play, but again for a time span of 40-50 years that's just not feasible. Also, socially acceptable or not, violent and aggressive men typically don't have problems finding sexual partners; Ted Bundy, the notorious serial killer and rapist, was known to receive many love-letters in prison, even after the details of his crimes (exclusively against women and girls) were made public and he was able to marry and conceive a child while incarcerated.