I would argue that a combination of brawn and brain is best the case scenario. But that is just an opinion. As you said, it is survival of the fittest, whether it is life or death, or just societal acceptance. After all, the job of parent is to make sure their child is well prepared for the world. A choice of a partner is the first step.

Muscles means strength and physical dominance, brains guarantees intellectual superiority in an age which tech runs the world, EQ means being a well adjusted human being who is confident and a people person. Once again a combination is best, if possible.

In the end, it all comes down to individual choice. People like who they like.