Modern Human Biology:

1
Chapter 16

• Modern Human Biology
• Patterns of Adaptation

2
Adaptive Significance of Human Variation

• Human variation is the result of adaptations to
  the environment
• Physiological response to the environment
  operates at two levels
• Long-term evolutionary changes
• Short-term, temporary changes
• Terms
• Homeostasis
• Acclimatization

3
Geographical Distribution of Skin Color in
Indigenous Populations
4
Ultraviolet Light and Skin Cells
5
Three Points Skin Color and Evolution

1. Early hominids lived in the tropics, where solar
   radiation is more intense than in temperate areas
   to the north and south.
2. Unlike modern city dwellers, early hominids spent
   their days outdoors.
3. Early hominids didnt wear clothing that would
   have protected them from the sun.

6
Thermal Environment

• Humans are found in a wide variety of thermal
  environments, ranging from 120 F to -60 F.

7
Human Response to Heat

• Long-term adaptations to heat evolved in our
  ancestors
• Sweat Glands
• Vasodilation
• Bergmann's rule - body size tends to be greater
  in populations that live in cold environments.

8
Bergmanns Rule
9
Allens Rule
10
Examples of Bergmanns andAllens Rules

• (a) This African woman has the linear proportions
  characteristic of many inhabitants of sub-Saharan
  Africa.
• (b) By comparison, the Inuit woman is short and
  stocky.

11
Human Response to Cold

• Short-term responses to cold
• Metabolic rate and shivering
• Narrowing of blood vessels to reduce blood flow
  from the skin, vasoconstriction.
• Increases in metabolic rate to release energy in
  the form of heat.

12
High Altitude

• Multiple factors produce stress on the human body
  at higher altitudes
• Hypoxia (reduced available oxygen)
• Intense solar radiation
• Cold
• Low humidity
• Wind (which amplifies cold stress)

13
Infectious Disease
14
Environment