The notion that members of one race are inherently more intelligent than members of another – brought back into circulation by the appointment of Andrew Sabisky, who claims that black Americans have a lower average IQ than white people, as a Downing Street adviser – is an idea with a deep and disturbing history.

In modern times, the study most often rolled out as supporting “evidence” is a 2006 work from the English psychologist Richard Lynn. In the publication, Lynn concluded that black Africans had an average IQ of less than 70, compared with the average western IQ of 100. This, he claimed, explained the low level of economic development in sub-Saharan Africa.

It was four years before the work was roundly discredited. In 2010, researchers found that Lynn had systematically ignored Africans with high IQ scores, but that was far from the only problem they uncovered, and at the end of their analysis they declared there was no evidence to support Lynn’s claims.

Not that this debunking undid the damage. James Watson, who co-discovered the structure of DNA, referenced Lynn’s study during his own foray into the matter. In 2007, Watson declared he was “inherently gloomy” about Africa’s prospects because “all our social policies are based on the fact that their intelligence is the same as ours, whereas all the testing says, not really”.

Watson apologised for his remarks, but later appeared to reassert them when he told a 2019 PBS documentary that differences in IQ scores between blacks and whites were driven by genetics. When asked to comment on the furore, Francis Collins, a leading geneticist and director of the US National Institutes of Health, said he was unaware of any credible research that backed up Watson’s view. He expressed his dismay that a prominent scientist was perpetuating “such scientifically unsupported and hurtful beliefs”.