In this issue of 'Wellcome News' we describe several fascinating studies that we have helped to fund, demonstrating different aspects of recent evolution in humans – and in the parasites and bacteria that evolve with us and cause much misery.

New research has shown that the evolution of the ability to digest milk has arisen independently a number of times (so-called convergent evolution). Most adults in the world are intolerant to milk. After weaning, the gene for the enzyme lactase, which breaks down the major sugar in milk – lactose – into easily absorbable sugars, is switched off. In regions of the world with a strong pastoral tradition, however, lactose tolerance commonly persists into adulthood. Most adults in these regions carry a regulatory variant of the lactase gene that allows lactase production throughout life. This must bring with it a survival advantage to reproductive age.

The genetic basis of lactose tolerance is well understood in European populations. An international team of researchers, including Panos Deloukas at the Wellcome Trust Sanger Institute, has found that lactose tolerance in East African adults is served by three newly discovered variants of the lactase gene, which have evolved independently of the European alleles.

Evolution occurs very rapidly in some organisms, such as viruses, bacteria and parasites. We see this in the study led by Mark Achtman (with researchers at the Sanger Institute and our Major Overseas Programme in Vietnam), which has shown that the use of antibiotics is a key driver of rapid evolution in certain genes of Salmonella enterica serovar Typhi, the bacterium causing typhoid fever. In another study, Daniel Jeffares, Emmanouil Dermitzakis and Matthew Berriman have identified that the genes responsible for the 'arms race' of host–cell interactions are the most rapidly evolving in the malaria-causing parasite Plasmodium falciparum.

The Y chromosome is the male sex-determining chromosome in humans. It has been a useful tool for studying human evolution, as very little recombination occurs during reproduction and therefore the Y chromosome changes slowly, and because it is passed on only down the male line. We are now finding that this conservative chromosome can tell more than we previously thought about ourselves.

Mark Jobling and colleagues at the University of Leicester have been exploring Y-chromosome variation for some years now, including some fascinating work on the relationship between male surnames and the Y chromosome. In their latest work, the team has identified the first genetic evidence of African input into the 'indigenous' British gene pool. Their descendants, living across the UK today, were unaware of their African ancestry. The study found that one-third of men with a certain rare Yorkshire surname carry a rare Y-chromosome type previously found only among people of West African origin. The research is further evidence of the complexity of genetic inheritance of the UK population, and reminds us of the care needed when drawing conclusions about people's origins from genetic data.

Mark Walport

Director of the Wellcome Trust