• We stated that there have probably been fewer than 25,000 generations since the human lineage split from that of chimpanzees (19 April, p 30). As several readers have spotted, there was a missing zero: it should have said 250,000.
• In the graph accompanying our evolution special (19 April, p 33), the red line in the top graph should not have been there. We should also have stated that the simulation models diploid individuals. This is why, in the population of 10, the fraction of the population with a particular mutation varies in steps of 0.05 rather than 0.1.
