The traditional terms „race“ and „racial group (type)“, referring to a division of humankind possessing a combination of physical traits that characterize it as a distinet human type, are no longer usable. Even in the past, the concept of race was far from unambiguous: Darwin gave examples of' classifications of' humans that ranged from two to sixty-three different varieties. The modern view of the concept of race recognizes that mass migrations as well as mixed marriages have occurred so frequently during the last several centuries that the so-called races are for the most part no longer definably distinet. Two approaches are now used to discuss human physical variety. One is clinal: a cline is a gradient of morphological or physiological change in a group of related organisms, usually along a line of geographical or environmental transition. For example, if one maps the distribution (presence or absence) of epicanthus or of the degree of skin pigmentation in the world's populations, one realizes that physical traits are not covariant. The second approach is to recognize that a breeding population has a noticeable frequency of' certain genes in comparison or contrast with other populations.