The problem is that diversity, when encountered in nature, is often accompanied by selection. Some diversity confers no competitive advantage, while some does.

The problem is that diversity, when encountered in nature, is often accompanied by selection. Some diversity confers no competitive advantage, while some does. In our social species, selection of some and not others is...controversial. The easiest way to avoid controversy is to demonstrate that there is no diversity, as was the consensus on cognitive differences between the sexes that this article challenges. Acknowledging biological differences is opening a door that many don't want to walk through.