• Modern humans (Homo sapiens)

How is human diversity perceived?Traditionally as distinctly different races

• Many attempts to classify human diversity• Carleton Coon. 1965. The Living Races of Man• Five races proposed:

– Caucasians– Asians– Indiginous Australians– Black Africans– San or Bushmen from Africa

• How do biologists perceive races in non-human species?

• A biological race = a subspecies.

• Phenotypically diagnosable populations occupying allopatric subdivisions of the range of a species.

• These populations have accumulated different mutations.

• Therefore, they express different fixed characteristics.

Example of subspecies

Colaptes auratus cafer

Colaptes auratus auratus

Example of subspecies: ratsnake (Elaphe obsoleta

Discordant characterSystems: also found inhumans

Genetic differencesdon’t coincide withcolor pattern differences

• Human race concept.• There is no satisfactory biological definition of a

human race!• Misconception: there are character states

unique to particular groups of humans• The characters traditionally used are quantitative

characters with continuous variation.

“Racial” characters arequantitative characterscontinuous characterse.g. skin color

Phenotypic expressionin and among populationsgenerally fits a normal distribution

A common “racial” characteristic is skin color.

Melanosomes

• All individuals have approximately the same number of melanocytes.

• Therefore, what is the basis of skin color differences?

• Can “races” be recognized based on skin color?

These groups easy to identify because of non-overlapping variation.

Gaps

685 nm

Skin color in 22 human populationsSamples of malesMean +/- one standard deviation