A kind of biological trait distribution in which there is a continuous, progressive gradation moving from one geographic region to another. The gradual decrease in frequency of the B blood allele going west in Europe is an example of this trend.

A kind of biological trait distribution in which there are relatively isolated pockets with relatively high frequencies of people who have a particular trait or variation of a trait.

A model or system for classifying people based on the false assumption that humans can be unambiguously placed into "races" on the basis of selected traits such as skin color, hair form, and body shape. Advocates of this approach incorrectly believe that there are more or less distinct populations of people from different geographic regions. This model is the basis for our “folk categories” of race widely used around the world.

A model or system for classifying people based on the assumption that the only biologically distinct groups are long isolated breeding populations whose evolutionary paths have separated from other populations.

A model or system for classifying people based on the fact that genetically inherited traits often gradually change in frequency from one geographic region to another--that is, they change in clines or progressively changing zones of degree difference with movement from one region to another.

The most commonly known human blood typing system in which there are 4 distinct types: A, B, AB, and O. An individual inherits one of these types from his or her parents and does not change it throughout life.

Any of the distinct varieties of humanity assumed by some people to exist, based on the discredited typological model of human variation. Such groups are commonly distinguished on the basis of visibly observable traits such as skin color, hair form, and body shape. These archaic concepts of physical types have little biological reality. They do, however, generally reflect socially recognized culturally defined ethnic groupings of people.

The presumed human "race" consisting of Europeans and other closely related people. The classification is based on the discredited typological model. The term was derived from the Caucasus Mountains southeast of Europe between the Black and Caspian Seas. This region was once thought to be the homeland of these people.

The presumed human "race" consisting of Asians and other closely related people. This classification is based on the discredited typological model. The term was derived from the Mongolians of north central Asia.

The presumed human "race" consisting mostly of Sub-Saharan Africans. This classification is based on the discredited typological model. The term was derived from the Latin word for the color black.

The most common ABO blood type around the world. It is particularly high in frequency among the indigenous populations of Central and South America, where it approaches 100%.

The rarest ABO blood type in the world. It is at its highest in central Asia where only 20-30% of the people have it. This blood type is lowest among the indigenous populations of the Americas and Australia.

The second most rare ABO blood type around the world—10-35% of the people in most populations have it. It is at its highest frequencies in small, unrelated populations, especially the Blackfoot Indians of Montana, the Australian Aborigines, and the Lapps, or Saami people, of Northern Scandinavia. It apparently was absent among Central and South American Indians.

The Diego blood type that is only found among Native Americans and East Asians. This nonrandom distribution pattern fits well with the hypothesis of an East Asian origin for Native Americans.