During decades of watching both collegiate and professional football, I have seen hundreds of touchdowns scored by black players - but not one extra point kicked by a black player.
Is this because blacks are genetically incapable of kicking a football or because racists won't let blacks kick a football?
Most of us would consider either of these explanations ridiculous. Yet genes and discrimination were the predominant explanations of black-white differences offered by intellectuals in the 20th century.
It was genes that were the preferred explanation in the early decades of that century and discrimination in the later decades, as I show in my recent book, "Intellectuals and Race."
The intelligentsia did not simply offer these as possible explanations among others. On the contrary, each was offered as the predominant, if not exclusive, explanation.
Anyone who said otherwise risked being dismissed as a "sentimentalist" in the early 20th century or denounced as a "racist" in later years.
Out of such dogmatic insistence on some one-size-fits-all theory came racial quotas and "disparate impact" lawsuits in our times, based on the presumption that racial differences in outcomes show that somebody did somebody else wrong.
In earlier times, the prevailing theory was that differences in outcomes show that some races are inferior to others. This led to such things as eugenics and ultimately to the Holocaust.
In both eras, the prevailing theory flattered the egos of the intellectuals - first as saviors of their race, and later as rescuers of victims of racism.
Among the alternative explanations of group differences that were ignored were geography, demography and culture.
For example, people with the geographic handicap of living in isolated mountain valleys have seldom, if ever, produced world-class achievements that advanced science, technology or philosophy.
On the contrary, people in such places have almost invariably lagged behind the progress in the rest of the world - including people of the very same race living on the plains below.