Human variability
There are many sources of human variability, including biological inheritance, natural selection, chance mutation, culture, and environment. Variability which limits activities in some way is generally regarded as a disability but this label is often contentious; for example, many who are deaf do not see themselves as being disabled.There are several misconceptions which have historically misled people about human variability. In Europe, where extensive intermixing over centuries, even millennia, has produced a more or less homogeneous population, minor differences in language and culture have misled certain people (e.g. the Nazis) to believe that significant differences exist between different national populations. With respect to the peoples of Africa, where modern man (Homo sapiens) originated about 80,000 years ago, the surface characteristic of skin color has masked the extensive variabilty which has built up over the tens of millennia with respect to numerous other characteristics.
Many genetic variations which are considered undesirable are governed by recessive genes, and therefore arise from matings of people who do not display the characteristic. In modern times many of these variations have been identified and in some cases can be detected before conception of a child or while the child is still in vitro, raising the possibility of abortion.
Common Human Variations
See also