Race or Human Genetic DiversityRace or Human Genetic Diversity

How do we study human How do we study human variation?variation?

Classification by • Races or the whole bodied

approach: a taxonomy of human types spread over geographic space

• Clines or the disembodied approach: mapping of individual human traits spread over geographic space

Basis of the Racial Approach: Genealogical Tree of Humanity

a b c d e i j k l ng m o phf

1 2 3 4 5 6 7 8

A B C D

I IIYellow arrows show gene flow between geographic regions

Depending on the issue, any one of the levels could be a racial group or grouping

Ancestor of all humans

Racial Phylogenetic Tree Based on Blood Proteins etc.Racial Phylogenetic Tree Based on Blood Proteins etc.

Another racial Another racial map of genetic map of genetic

variation using a variation using a different set of different set of

genetic markersgenetic markers

Conventional Conventional Phylogenetic Phylogenetic ““TreeTree””

of human of human ““racesraces””

Out of Africa: Out of Africa: Again and Again and

AgainAgain

Source: A. Templeton Nature416, 45 -51 (07 Mar 2002)

Partitioning of Racial VariationPartitioning of Racial Variation

An example of the An example of the clinalclinal approach to approach to human variation: map of skin colorhuman variation: map of skin color

Some Issues in Racial TypologiesSome Issues in Racial TypologiesRaces are not discrete groups

True, but they are fuzzy sets that comprise collections of characteristics that go together.

Classification is based on arbitrary characteristicsMany important diagnostic traits are included and members are more closely related to on another than they are to those in other groups and they have different geographic origins

From a standard biological definition, genetic distances between races are not great enough to call them races

True, but what do we call them? Geographic populations? Ethnicgroups?

Physical variation over space does not occur abruptly but rathergradually

Both true and falseThere is no association between race and culture

TrueCompared to other species with world-wide distributions there is very little genetic variation among human populations

True

Some issues in racial Some issues in racial classificationclassification

If you group people into standard racial classifications there is more genetic similarity within than between groupsForensic anthropologists can identify race through skeletal remains (as well as sex and age)Human bodies are integrated wholes and it is important to understand how traits complexes develop and interrelateClassification helps us understand population historyRacial classification is important medically

Anatomically modern humans Anatomically modern humans filling up the worldfilling up the world

Culture can affect genetic structure: Culture can affect genetic structure: Lactose IntoleranceLactose Intolerance

Group Percent Lactose Intolerant

US whites 2-19

Finnish 8

Swiss 12

Swedes 4

US Blacks 70-77

Ibos 99

Bantu 90

Fulani 22

Thais 99

US Asians 95-100

AustralianAborigines 85

Whether or not members of an ethnic are able to digest milk sugar (lactose) in adulthood is dependent on their history of herding dairy animals