Even without a time machine to witness it, we can be certain that the evolutionary process has sorted away ancestors who failed to reproduce, leaving only those fit for the environment.

But like machine learning, we can never know why life “chose” one way over the other. Still, that any trait in us or other species, psychology or other, is selected by evolution must be true, as any trait selected away by evolution by definition does not live. The alternative explanation of our psychology would require a supernatural spiritual force, which is even harder to falsify with experiment than evolutionary psychology.

So to questions of “why” natural selection chose us who live now to have the psychology we have, can never be answered by experiment.

When we can’t find knowledge through experiment, wouldn’t logic deduction and educated guesses/models be the best method - leaving us with the flawed but but interesting subject of the evolution of our psychology