ABSTRACT
Phenotypic traits of humans, be they skin color, height, or diseases such as diabetes, are controlled by a combination of inherited and environmental factors, and stochastic developmental and molecular processes. Population geneticists, forensic geneticists, anthropologists, and archaeologists need labels to refer to social groups of human beings. The archaeological record consists of physical objects that have been shaped by human contact. Humans are not the only animals to make tools, but tools produced by earlier human ancestors or nonhuman species are difficult to distinguish from naturally occurring objects. To think of a single origin for an entire population is to misconceive how genetic diversity accumulates in a sexually reproducing, outbreeding species such as humans. Human populations are fluid entities, giving and receiving genes from neighboring populations all the time. Alleles enter the population at different times and from different places.
