Evolutionary biology has always been controversial. Not controversial among biologists, but controversial among the general public. This is largely because Darwin’s theory directly contradicted the supernatural accounts of human origins rooted in religious tradition and replaced them with fully natural ones. The philosopher Daniel Dennett has described evolution as a sort of “universal acid” that “eats through just about every traditional concept, and leaves in its wake a revolutionized world-view, with most of the old landmarks still recognizable, but transformed in fundamental ways.” Fearing this corrosive idea, opposition in the US to evolution mainly came from Right-wing evangelical Christians who believed God created life in its present form, as described in Genesis.

In the 1990s and 2000s there were repeated attempts by evangelicals to ban evolution in public schools or teach the so-called “controversy” by including Intelligent Design—the belief that life is too complex to have evolved without the aid of some “Intelligent Designer” (i.e. God)—in the biology curriculum alongside evolution. But these attempts failed when scientists demonstrated in court that Intelligent Design was nothing more than Biblical Creationism gussied up in scientific-sounding prose. Since then, however, Creationism and Intelligent Design have lost a tremendous amount of momentum and influence. But while these right-wing anti-evolution movements withered to irrelevancy, a much more cryptic form of left-wing evolution denialism has been slowly growing.

At first, left-wing pushback to evolution appeared largely in response to the field of human evolutionary psychology. Since Darwin, scientists have successfully applied evolutionary principles to understand the behavior of animals, often with regard to sex differences. However, when scientists began applying their knowledge of the evolutionary underpinnings of animal behavior to humans, the advancing universal acid began to threaten beliefs held sacrosanct by the Left. The group that most fervently opposed, and still opposes, evolutionary explanations for behavioral sex differences in humans were/are social justice activists. Evolutionary explanations for human behavior challenge their a priori commitment to “Blank Slate” psychology—the belief that male and female brains in humans start out identical and that all behavior, sex-linked or otherwise, is entirely the result of differences in socialization.