Human variabilityHumans vary naturally due to genetic inheritance over a wide range. Additional variability is introduced as people survive various injuries. Variability which limits activities in some way is generally regarded as disability but that label may be rejected by those such as the deaf which it may be applied to.
There are several misconceptions which have historically mislead people about human variability: In Europe where extensive intermixing over centuries, even millenia, has produced a more or less homogeneous population, minor differences in language and culture have misled certain people (e.g. the Nazis) into the notion that significant differences exist as between different national populations. With respect to the peoples of Africa where modern man 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 millenia with respect to numerous other characteristics.
Many genetic variations which are considered undesirable are governed by recessive genes thus arising from matings of people who do not display the characteristic. In modern times many of these variations have been indentified and in some cases can be detected before conception or a child or while the child is still in vitro raising the possibility of abortion.