There are two questions that arise out of the furore over James Watson's comments. Is race a valid scientific category? And should scientists refrain, for moral reasons, from speculating about racial differences?
There are clearly genetic differences between human populations. North Europeans are more likely to suffer from cystic fibrosis. Tay Sachs disease particularly affects Ashkenazi Jews. Beta blockers seem less effective on African Americans.
Yet race is rarely a good guide to the distribution of genes. We all know, for instance, that sickle cell anaemia is a black disease. Except that it isn't. It's a disease of populations originating from areas with high incidence of malaria. Some are black, some are not. The sickle cell gene is found in parts of equatorial Africa, southern Europe, the Middle East and central India. Most people, however, know that African Americas suffer disproportionately from the trait. And they automatically assume that what applies to black Americans also applies to all blacks and only to blacks.
What the sickle cell story shows is that genes do not respect the socially defined boundaries of human groups. The distribution of genes rarely matches the distribution of populations. What we call races are often irrelevant to the study of gene distributions. Genetic variation among Africans is often greater than that between blacks and whites. Sub-Saharan Africans and Australian Aborigines are both labelled 'black'. Yet, there are few populations that are genetically more distinct.
If the relationship between race and disease is fraught, that between race and intelligence is even more so. Intelligence has never been properly defined, no one knows what IQ tests actually measure, and we have yet to identify the genes that underlie the myriad of attributes that collectively give rise to intelligence. Given all this, making simplistic claims about the racial distribution of intelligence smacks more of alchemy than of science.
In my opinion, James Watson got his facts in a double helix. But did he have the right to speculate about race and intelligence in the first place? I believe he did. When the Science Museum cancelled Watson's lecture last week, it claimed that 'he had gone beyond the point of acceptable debate'. Nonsense. It is as legitimate for Watson to express his opinion as it is for me to express mine, even if that opinion is factually wrong, morally suspect and politically offensive. That is the essence of scientific debate.