Chapter 15 Human Variation and Adaptation Historical Views of Human Variation Contemporary Interpretations of Human Population Diversity Racism Intelligence The Adaptive Significance of Human Variation Infectious Disease

Historical Views of Human Variation Monogenism - all humans descended from one pair. Polygenism - all humans descended from a number of pairs. Biological determinism - aspects of behavior are governed by genetics. Eugenics - concept of “race improvement”

The Concept of Race All modern humans belong to the same polytypic species, Homo sapiens. A polytypic species consists of local populations that differ from one another in the expression of one or more traits.

Racism Based on the false belief that intellect and cultural factors are inherited along with physical characteristics. Such beliefs rest on the assumption that one's own group is superior to other groups. Racism is a cultural, not a biological phenomenon, and is found worldwide.

Intelligence Genetic and environmental factors contribute to intelligence. Many psychologists say that IQ scores measure life experience. There is no convincing evidence that populations vary with regard to cognitive abilities.

The Adaptive Significance of Human Variation Human variation is the result of adaptations to environmental conditions. Levels of response to environmental change: Long-term (i.e. genetic) evolutionary changes characterize all individuals within a population or species. Short-term physiological response to environmental change is temporary.

Pigmentation and Geographical Divisions Before 1500, skin color in populations followed a geographical distribution. Populations with the greatest amount of pigmentation are found in the tropics. Populations with lighter skin color are associated with more northern latitudes.

Human Response to Heat Long-term adaptations to heat evolved in our ancestors: Sweat Glands Vasodilation

Relationship between body size, proportions and climate Bergmann's rule - body size tends to be greater in populations that live in cold environments. Allen’s rule: Shorter appendages, with increased mass to surface ratio are adaptive because they are more effective at preventing heat loss.

Infectious Disease Caused by invading organisms such as bacteria, viruses, or fungi. Have exerted enormous selective pressures on human populations. Influences the frequency of certain alleles that affect the immune response.

Small Pox The only disease eliminated as a result of modern medical technology Higher incidence in those with type A or AB blood than those with type O blood. Virus has an antigen similar to the A antigen. The immune systems of individuals with type A antigen may not recognize the small pox antigen as a threat.

Impact of Infectious Disease Since the 1940s - antibiotics have reduced the mortality rate. Late 1960s - surgeon general declared the war against infectious disease won Between 1980 and 1992 - deaths increased by 58% (possibly due to overuse of antibiotics).

Environmental Factors. Global warming may expand the range of tropical diseases. The rapid spread of disease is associated with encountering people everyday (includes crossing borders) Overcrowding leads to unsanitary conditions and the spread of communicable disease.