ANTH 101, Chapter 5 Notes
Brief History of the Race Concept
Race is the classification of human variation.
Early written records do not use the idea.
Some argue the race concept started during the Renaissance.
Other early race concepts began in the eighteenth century.
Blumenbach’s study of skulls in 1775 established a racial taxonomy.
Blumenbach (German physician, died 1840)
Classified humans into races according to skin color
Classifications arbitrary, he recognized overlapping
Cephalic index describes shape of head
Head width ÷ head length x 100 = C.I.
Long, narrow head = Dolichocephalic (<75%), northern Europeans
Mesocephalic between 75 and 80%
Broad head = Brachycephalic (>80%), southern Europeans
Using skin color combined with the cephalic index, Blumenthal ranked the “races” from higher
to lower in terms of intelligence.
Debunking the Race Concept: Franz Boas Shows that Human Biology Is Not Static
Franz Boas was among the first to challenge the taxonomy of human variation.
Boas examined the cephalic index and found no relationship to racial types.
So-Called Racial Traits Do Not Fall into Distinct Groups
Robert Lewontin studied global genetic variation.
Racial groups accounted for only 5–10 % of variation.
Most variation cuts across groups regardless of “race.”
Human Variation: Geographic Cline, Not Racial Categories
Specific biological traits follow a geographical gradient (cline).
Skin pigmentation is an example.
So, what is the significance of modern human variation?
And, what is the source of this variation?
Human variation is the result of both short-term and long-term adaptation.
Much Variation is the Result of the Growth Cycle: Conception through Adulthood
Divided into three stages:
Prenatal (conception to birth)
Postnatal (birth to twelve years)
Adult (12 thru senescence)
Prenatal Stage: Sensitive to Environmental Stress, Predictive of Adult Health
Pregnancy lasts nine months.
Involves rapid growth and development, especially of the brain.
Pre-birth stressors can influence diseases a person may develop later in life
(mothers diet, chemical dependencies, health conditions).
Postnatal Stage: The Maturing Brain, Preparing for Adulthood
Divided into five periods characterized by different growth velocities.
Devel. of brain, dentition, motor & cognitive skills, sexual dimorphism, skeletal
structure.
Environmental effects during childhood influence growth and development.
trends in height; changes in stature caused by environment.
Adult Stage: Aging and Senescence
Aging refers to social, cultural, biological events that occur over a lifetime.
Senescence is a reduction of the body’s ability to respond to stress (homeostasis).
Cessation of reproduction in women is called menopause.
Evolution of Human Life History: Food, Sex, and Strategies for Survival and Reproduction
Survival and adaptive success are due to food acquisition and reproduction.
Humans are influenced by culture.
Life history develops with human culture.
Prolonged Childhood: Fat-Bodied Moms and Their Big-Brained Babies
Humans have a prolonged childhood with high maternal investment
Grandmothering: Part of Human Adaptive Success
Postreproductive survival is high with humans.
Women play a large role in caring for children’s children.
Adaptation to the environment occurs at four levels.
Genetic , Developmental , Physiological (acclimatization), Behavioral (culture)
Heat Stress and Thermoregulation
Body maintains core temperature under hot conditions through vasodilation & sweating.
Humans have a strong ability to adjust to heat.
Body Shape and Adaptation to Heat Stress
Bergmann’s rule: Heat-adapted mammals will have higher surface-area-to-body ratio.
Allen’s rule: Heat-adapted mammals will have long limbs.
Rules explain variation in human body shapes going back 1.5 million years.
Solar Radiation and Vitamin D Synthesis
The body needs UV radiation to synthesize vitamin D.
Vitamin D is crucial in calcium absorption, bone mineralization.
Solar Radiation and Skin Color
Best predictor of skin color is UV radiation exposure.
More pigmentation is associated with high UV.
High Altitude and Access to Oxygen
Humans suffer from hypoxia (lack of available oxygen) at high altitudes.
The body responds through production of extra red blood cells and hemoglobin, increases
diameter of blood vessels.
Those born at high altitudes have greater lung volume and larger chest cavities as well as
the above characteristics.
Nutritional Adaptation: Energy, Nutrients and Function
Each human body requires certain energy and nutrients to function.
Basal metabolic requirement (basic body functioning)
Total daily energy expenditure (energy needed for BMR plus work, exercise, etc.)
Human Nutrition Today
Most populations are undernourished and consume too few calories.
Efforts to combat this problem have resulted in new nutritional issues.
Overnutrition and the Consequences of Dietary Excess
Dietary excess is as serious a problem as dietary lack.
Obesity is an increasing problem in the U.S., especially among children, as well as in the
Pacific, Europe, Middle East, Latin America, and South Africa.
Obesity can lead to high cholesterol, heart disease, diabetes.
May have resulted from genetic traits that allowed for conservation of nutrition
during times of famine (thrifty genotype)
Workload Adaptation: Skeletal Homeostasis and Function
Bone growth affected by disease, physiological processes, nutrition, & mechanical forces.
Wolff’s law states that bone is produced where it is needed and removed where it is not.
Activity or the lack of it can change the shape of skeletal elements.
Excess Activity and Reproductive Ecology
Benefits of exercise are well documented.
Excessive workload or exercise can interrupt female reproduction, lowering fertility
levels.
Excessive workload potentially can lower birthrates in certain groups or populations.
Work or exercise becomes a selective factor in evolution.