Transcript Chapter 13 Modern Human Diversity

Chapter 13
Modern Human Diversity
Chapter Outline
What are the causes of physical
variability in animals?
 Is the biological concept of race useful
for studying physical variation in the
human species?
 Is there validity to studying differences
in intelligence from one population to
another?

Variation and Evolution
In humans, most behavioral patterns
are culturally learned or acquired.
 Other characteristics are determined by
an interaction between genes and
environment.

Genetic Variability
Gene pools of populations contain
various alternative alleles.
 When the environment changes, their
gene pool confers the possibility for
physical alteration to meet the change.
 When a species is separated into
different regions, populations differ in
the frequency with which genetic
variability is expressed.

Frequency of Alleles for the
A, B, and O Blood Groups
The Meaning of Race
Early anthropologists classified Homo
sapiens into races based on geographic
location, skin color, body size, head
shape, and hair texture.
 The presence of individuals who did not
fit the “type” challenged these racial
classifications.
 No examples of pure racial types could
be found.

East-west Gradient in
Frequency of Type B Blood in
Europe
Race and Human
Variation: Limitations
Race is an arbitrary category, making
agreement on any classification
impossible.
 Humans are complex genetically and
often the genetic basis of traits on
which racial studies are based is poorly
understood.
 Race exists as a cultural as well as a
biological category.

Distribution of Human Skin
Pigmentation Before 1492
Factors in Variation of
Skin Color
Transparency or thickness of the skin.
 Distribution of blood vessels.
 Amount of carotene and melanin in a
given area of skin.

Factors in Variation of
Skin Color
Exposure to sunlight increases the
amount of melanin, darkening the skin.
 Selective mating, as well as geographic
location, plays a part in skin color
distribution.

Racism
Racism is a social problem.
 Racist individuals react on the basis of
social stereotypes instead of scientific
facts.
 Behavioral characteristics attributed to
race can be explained with culture
rather than biology.

Decline in Human Male
Sperm Counts