title: Corrections and clarifications.
abstract: Reference 4 in the article "Demic expansions and human evolution" by L. L. Cavalli-Sforza et al. (29 Jan., p. 639) was incorrect. It should have read as follows: "F. Weidenreich, Evolution 1, 221 (1947); C. Coon, The Living Races of Man (Knopf, New York, 1965); M. H. Wolpoff, in (2), pp. 62-108."