 A stronger anthropological rejection of the biological conception of race was leveled by Ashley Montagu (1905–1999). Drawing on insights from modern, experimental genetics, Montagu forcefully argued that the anthropological conception of race relied on grouping together various perceptible physical characteristics, whereas the real building blocks of evolution were genes, which dictated biological changes among populations at a much finer level. The morphological traits associated with race, thus, were gross aggregates of a variety of genetic changes, some of which resulted in physically perceptible characteristics, many others of which resulted in imperceptible changes. Moreover, since genetic evolution can occur through both the mixture of different genes and the mutation of the same gene over generations, the traits associated with races cannot be attributed to discrete lines of genetic descent, since the dark skin and curly hair of one individual may result from genetic mixture while the same traits in another individual may result from genetic mutation (Bernasconi and Lott 2000, 100–107). Montagu’s efforts eventually resulted in the publication of an official statement denying the biological foundations of race by the United Nations Educational, Scientific, and Cultural Organization (UNESCO) in 1950, although it would take until 1996 for the American Association of Physical Anthropologists (AAPA) to publish a similar document (Brace 2005, 239).