“We found multiple cases in which plants had evolved highly specialized dimorphism ... According to Suissa, because ferns lack seeds, fruits, or flowers, they have an incredible flexibility ...

This means that sexual dimorphism—the physical differences between the males and females of a species—is increasing for humans, all thanks to improved standards of living over time.

Sexual Dimorphism in the Animal Kingdom; a Theory of the Evolution of Secondary Sexual Characters. By J. T. Cunningham Pp. xi + 317; with 32 illustrations. (London: Adam and Charles Black ...