Evolutionary theorists struggle to say why humans, unique among animals, have a bony protuberance at the end of the jaw.

Their studies revealed high levels of heterozygosity relative to the predictions of most evolutionary theorists.

In the 1960s, as evolutionary theorists explored the possibility of multiple units of selection, ecologists turned to evolutionary approaches.

The existence of altruistic behaviors has been a difficult problem for evolutionary theorists from the beginning.