1. Anthropology: The Exploration of Human Diversity5
Human Variation and Adaptation
Anthropology: The Exploration of Human Diversity
11th Edition
Conrad Phillip Kottak

2. Human Variation and Adaptation
Race: A Discredited Concept in Biology
Human Biological Adaptation

3. Race: A Discredited Concept in Biology
Race refers to geographically isolated subdivision of a species
Members of race or subspecies share distinctive physical characteristics based on common ancestry and inheritance of same genes
Human populations have not been isolated enough from one another to develop into discrete races

4. Race: A Discredited Concept in Biology
Human populations vary biologically, but because of extensive gene flow and interbreeding, there are no sharp breaks between populations
Human biological variation distributed gradually between populations along clines

5. Race: A Discredited Concept in Biology
Scientists have trouble grouping people into distinct racial units
Race is supposed to reflect shared genetic material
Early scholars used phenotypical traits (skin color) for racial classification

6. Race: A Discredited Concept in Biology
Races Are Not Biologically Distinct
Obvious problem with “color-based” racial labels is that terms don’t accurately describe skin color
Another problem with tripartite scheme is that many populations don’t neatly fit into one of the three “great races”

7. Race: A Discredited Concept in Biology
Racial classifications based on phenotype lack credibility because similarities and differences don’t necessarily have genetic basis

8. Race: A Discredited Concept in Biology
Explaining Skin Color
Natural selection—process by which nature selects the forms most fit to survive and reproduce in a given environment

9. Race: A Discredited Concept in Biology
Explaining Skin Color
Skin color influenced by several genes
Melanin—primary determinant of human skin color; chemical substance manufactured in the epidermis
Prior to 16th century, darker skinned populations closest to the equator

10. Race: A Discredited Concept in Biology
Explaining Skin Color
Skin color influenced by several genes
Unprotected humans in tropics face threat of severe sunburn
Increases susceptibility to disease
Impairs the body’s ability to withstand heat by reducing the skin’s ability to sweat
Light skin is more susceptible to skin cancer.
Loomis suggested that in tropics, dark skin color protects body against overproduction of vitamin D

11. Human Biological Adaptation
Abundant evidence for human genetic adaptation and evolution through selection working in specific environments

12. Human Biological Adaptation
Genes and Disease
According to World Health Report, tropical diseases affect more than 10 percent of world’s population
Malaria—300 million to 500 million people
Schistosomiasis—more than 200 million
Filarisasis—120 million

13. Human Biological Adaptation
Genes and Disease
Microbes major selective agent for humans, particularly before arrival of modern medicine
After food production emerged, infectious diseases pose mounting risk and became foremost cause of human mortality
ABO blood groups vary in resistance to disease

14. Human Biological Adaptation
Genes and Disease
In diseases for which there are no effective drugs, genetic resistance maintains significance
There is probably genetic variation in susceptibility to HIV
AIDS could cause large shifts in human gene frequencies

15. Human Biological Adaptation
Facial Features
Natural selection also affects facial features
Long noses seem to be adaptive in arid areas and cold environments
Thomson’s Nose Rule—association between nose form and temperature

16. Human Biological Adaptation
Size and Body Build
Bergmann’s rule—smaller of two bodies similar in shape has more surface area per unit of weight
Average body size tends to increase and cold areas and decrease in hot ones
Allen’s rule—relative size of protruding body parts—ears, tails, bills, fingers, toes, and limbs—increase with temperature

17. Human Biological Adaptation
Size and Body Build
Human populations use different, but equally effective, biological means of adapting to environmental stresses associated with high altitudes

18. Human Biological Adaptation
Lactose Tolerance
Phenotypical adaptation—adaptive changes that occur during individual’s lifetime
Genes and phenotypical adaptation work together to produce a biochemical difference between human groups in ability to digest large amounts of milk
Adaptive advantage when other foods are scarce and milk available