Modern humans Homo sapiens

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• Modern humans (Homo sapiens)

How is human diversity perceived? Traditionally
as distinctly different races
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• Many attempts to classify human diversity
• Carleton Coon. 1965. The Living Races of Man
• Five races proposed
• Caucasoid
• Mongoloid
• Australoid
• Congoid
• Capoid

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• How are races perceived in non-human species?
• A biological race a subspecies.
• Phenotypically diagnosable populations occupying
  a subdivision of the range of a species.
• These populations have be exposed to different
  selection pressures.
• Therefore, they express a restricted set of
  adaptations

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Example of biological races (subspecies)
Colaptes auratus
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Example of subspecies ratsnake (Elaphe obsoleta
Discordant character systems
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• 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.

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Racial characters are quantitative
characters continuous characters e.g. skin
color Phenotypic expression in and among
populations generally fits a normal distribution
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A common racial characteristic is skin color.
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Melanosomes
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• 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?

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These groups easy to identify because of
non-overlapping variation.
Gaps
685 nm
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Skin color in 22 human populations Samples of
males Mean /- one standard deviation
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Global Patterns of Human Variation

• Can be examined genetically
• Can be examined phenotypically
• Are phenotypic differences concordant with
  genetic differences?

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Eight classes of genetic Similarity enzyme
blood group loci Arrayed by increasing difference
Distribution of eight classes of skin
pigmentation intensity
Concordance or discordance?
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• There IS geographic structuring of allele
  frequencies.
• Genetic distance map
• 42 native human populations
• 120 allele frequencies
• Closer proximity in graph greater genetic
  similarity
• Related to geographic distances among the groups.
• PPPPPopu

Populational differences
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Average genetic differences Distance curtails
gene flow among groups
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• Populational differences among human groups
• Today, human races are distinguished by ethnic
  differences NOT biological differences.
• Differences in culture
• nationality
• language
• religion
• Biologically, there is no Jewish race, no African
  race, no African-American race, etc.
• But, biological differences may still be
  emphasized, even in sociology.