Consider trait extroversion, which involves not only being more sociable, but also more adventurous and willing to take risks. In evolution, it would make strategic sense if stronger, more physically capable people exploited their bodily advantages by being more extroverted.

That’s exactly what some research has found. One study out of Germany’s University of Göttingen recently reported that of more than 200 men, those who were physically stronger and who had more “macho” bodies – including larger chests and biceps – also tended to be more extroverted, especially in the sense of being more assertive and physically active. The same strength-extroversion association was not found among the women in the study.

Other research has found that physically more formidable men also tend to be more prone to aggression and less neurotic (as in, less fearful and worrisome). Again, this makes sense if you see personality as an adaptive strategy. If you are physically weak, then being cautious and wary of danger is likely to lengthen your lifespan. But if you are physically formidable, you can afford to be more of a risk-taker.