SOME light was shone this week on the vexed question of the genetics of race in humans. Lluís Quintana-Murci and his colleagues at the Pasteur Institute, in Paris, published a study in Nature Genetics that looked at which genes have undergone recent natural selection at different rates in different parts of the world, and might thus contribute to any biological differences between races.

Given the fraught nature of the subject, the results are gratifyingly uncontroversial. Several of the differences Dr Quintana-Murci detected are in genes for the superficial racial markers of skin colour and hair form. Most of the others whose functions are known are connected either with diet or with resistance to disease.

Dr Quintana-Murci's data were drawn from a project called HapMap, which catalogues what are known as single-nucleotide polymorphisms, or SNPs. These are places where individual human genomes routinely differ from one another by a single genetic “letter”. If such a variation happens inside a gene, as opposed to occurring in part of the “junk” DNA that pads the genome out, the result can be a change of function of the gene in question—the raw material of evolution.

Applying various statistical techniques to the 2.8m SNPs so far catalogued by HapMap, Dr Quintana-Murci found 55 genes that showed evidence of having undergone significant localised evolution. Six controlled skin pigment and hair development. Four helped the immune system combat disease-causing organisms, such as malarial parasites, that are a problem in some places, but absent from others. A further six regulated metabolism in various ways, probably in response to the different diets enjoyed by different people. (Some of these genes are of wider interest as they are involved in obesity, diabetes and hypertension.) Nine others had various other jobs that were also of no political significance. All in all, the school of thought which holds that humans, for all their outward variety, are a pretty homogenous species received a boost.

There were, however, 30 locally selected genes whose functions are as yet unknown. And it is possible that others have been overlooked. This result promotes the brotherhood of man. But it is probably not the last word on the matter.