Race or Human Genetic Diversity
How do we study human
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
Ancestor of all humans
Yellow arrows show gene flow between geographic regions
I
II
A
B
1
a
2
b
c
C
3
d
e
4
f
g
D
5
h
i
6
j
k
7
l
n
8
m
Depending on the issue, any one of the levels
could be a racial group or grouping
o
p
Racial Phylogenetic Tree Based on Blood Proteins etc.
Another racial
map of genetic
variation using a
different set of
genetic markers
Conventional
Phylogenetic “Tree”
of human “races”
Out of Africa:
Again and
Again
Source: A. Templeton Nature416, 45 51 (07 Mar 2002)
Partitioning of Racial Variation
An example of the clinal approach to
human variation: map of skin color
Some Issues in Racial Typologies
¾ Races are not discrete groups
True, but they are fuzzy sets that comprise collections of
characteristics that go together.
¾ Classification is based on arbitrary characteristics
Many 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
¾ 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? Ethnic
groups?
¾ Physical variation over space does not occur abruptly but rather
gradually
Both true and false
¾ There is no association between race and culture
True
¾ Compared to other species with world-wide distributions there is very
little genetic variation among human populations
True
Some issues in racial
classification
z
z
z
z
z
If you group people into standard racial classifications
there is more genetic similarity within than between
groups
Forensic 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 interrelate
Classification helps us understand population history
Racial classification is important medically
Anatomically modern humans
filling up the world
Culture can affect genetic structure:
Lactose 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
Australian
Aborigines
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