Brief History of the Race Concept
The idea of race is a recent invention. Early written records do not employ the concept. The American physical anthropologist C. Loring Brace has argued that the race concept got its start in the 14th century, during the Renaissance. Before that time, peo
Brief History of the Race Concept: Blumenbach
The early scientific articulation of the race concept first emerged in the 18th century. Building on Linnaeus's taxonomy of organisms, the eminent German anatomist Johann Friedrich Blumenbach (1752-1840) developed a biological taxonomy of human races. Blu
Debunking the Race Concept: Franz Boas Shows that Human Biology Is Not Static
Franz Boas was among the first scientists to challenge the taxonomic approach to human biological variation. Specifically, he wanted to test the widely held notion that head shape and other so-called racial markers were static entities, essentially unchan
Lewontin: So-Called Racial Traits Are Not Concordant
In the early 1970s, the American geneticist R.C. Lewontin (b. 1929) tested the race concept by studying global genetic variation. If human races existed, most genetic diversity would be accounted for by them.
Focusing on blood groups, serum proteins, and
Human Variation: Geographic Clines, Not Racial Categories
One important finding from physical anthropologist's study of human variation is that specific biological traits generally follow a geographic continuum, also called a cline. Among the best examples of clinal variation are the skin pigmentations of living
Life History
The biology of growth and development.
The Growth Cycle: Conception through Adulthood
The human growth cycle, from embryo to fetus to child to adult, consists of three stages:
1) The prenatal stage, which includes the three periods, or trimesters, of pregnancy and ends with birth (9 months after conception).
2) The postnatal stage, which i
Prenatal Stage: Subcategories
The prenatal stage includes three periods, or trimesters, of pregnancy, and ends with birth, about 9 months after conception.
Postnatal Stage: Subcategories
1) Neonatal Period: 1st month
2) Infancy: 2nd month to end of lactation, usually by the end of the 3rd year
3) Childhood: Ages 3-7
4) Juvenile period: 7-10 for girls and 7-12 for boys
5) Puberty: Days or weeks
6) Adolescence: 5-10 years after puberty
Adult Stage: Subcategories
1) Reproductive period: Age 20 to the end of the childbearing years, usually by age 50 for women and later for men
2) Senescence: Period of time after the childbearing years.
Prenatal Stage: Sensitive to Environmental Stress, Predictive of Adult Health
In humans, the prenatal stage, or pregnancy, lasts nine months. Distinctive cell groupings first represent different kinds of tissues, then give rise to the various physiological systems. By the end of the second month, the embryo is about one inch long b
Postnatal Stage: Infancy
Each of the five postnatal periods has a different growth velocity, or rate of growth per year. During infancy, the period of most rapid growth, the deciduous (or primary) dentition erupts through the gums. By the time an infant has completed weaning, all
Postnatal Stage: Childhood
During childhood, general growth levels off, but the still rapidly growing brain requires the child to have a diet rich in fats, protein, and energy. The child learns behaviors important to later survival, but still depends on adults for food and other re
Postnatal Stage: Juvenile Period
By about age six, permanent teeth begin to replace primary teeth, and brain growth is completed. The eruption of the first permanent molar signals the ability to eat adult food, very high nutritional requirements ceasing once the brain reaches its final w
Postnatal Stage: Puberty and Adolescence
Adolescence presents a number of profound biological developments. Sexual maturation commences with puberty, and its visible characteristics are the beginning of breast development and menstruation (menarche) in girls, the deepening of the voice and emerg
Postnatal Stage: Puberty and Adolescence: Bone Growth
Prior to the completion of growth, the ends of the long bones�the humerus, radius, and ulna in the arm, and the femur, tibia, and fibula in the leg�are separate growth centers called epiphyses. The epiphyses are separated from the main shaft, or diaphysis
Postnatal Stage: Adulthood
Biologically, adulthood is signaled by the completion of sexual maturity, the reaching of full height, and the fusion of the epiphyses. The social and behavioral maturity associated with adulthood, however, are difficult to define.
Secular Trend: Height
This twentieth-century trend of increasing tallness, sometimes called a secular trend, has been noted in many other countries as well. Multiple factors have contributed to particular causes from place to place, but the collective increase in stature has r
Growth: Miscellaneous
The growth and development of males, prenatally and postnatally, are more sensitive to environmental insult than are the growth and development of females. When a period of growth disruption occurs before adulthood, the resulting height deficit can be mad
Adult Stage
Throughout life, the body continuously grows and develops. By adulthood, its basic structure has been formed, so during this period most growth and development involve the replacement of cells and of tissues.
Adult Stage: Aging and Senescence
Aging basically means "becoming older," but it refers collectively to various social, cultural, biological, and behavioral events that occur over a lifetime but do not by themselves increase the probability of death. Senescence, which accompanies aging, i
Adult Stage: Factors Accompanying Senescence
Whereas the previous life stages are generally predictable in their timing (mostly due to genetic programming), the chronology of senescence is highly variable. Menopause, the loss of ovarian function, is a key element of female senescence. Male and femal
Evolution of Human Life History: Food, Sex, and Strategies for Survival and Reproduction
Two behaviors make possible the survival and adaptive success of humans and other primates: acquisition of food and reproduction. Unlike other primates, humans acquire food and reproduce within the contexts of culture and society.
Prolonged Childhood: Fat-Bodied Moms and Their Big-Brained Babies
Humans have a relatively prolonged childhood. However, within this life period the spans of infancy and lactation are quite short. The mother's brief intensive child care allows her, theoretically, to have more births and to invest her resources among all
Grandmothering: Part of Human Adaptive Success
Humans are also the only primates that experience, at the other end of the life history, prolonged postmenopausal survival. Ethnographic evidence from cultures around the world shows that postmenopausal women, most often grandmothers, play important roles
Adaptation: Meeting the Challenges of Living
1) Genetic adaptation
2) Developmental adaptation
3) Acclimitization
4) Cultural adaptation
Genetic Adaptation
Genetic adaptation occurs at the population level via natural selection. Here, the biological change is inherited and is not reversible in a person.
Developmental (Ontogenetic) Adaptation
Developmental (or ontogenetic) adaptation occurs at the level of the individual during a critical period of growth and development, childhood especially. The capacity to make the change is inherited, but the change is not inherited and is not reversible.
Acclimitization (Physiological Adaptation)
Acclimitization (or physiological adaptation) occurs at the individual level, but unlike developmental adaptation it can occur anytime during a person's life. In this kind of adaptation, the change is not inherited and can be reversed.
Cultural (Behavioral) Adaptation
Lastly, cultural (or behavioral) adaptation involves the use of material culture to make living possible in certain settings.
Functional Adaptations
The American physical anthropologist Roberto Frisancho applies the term functional adaptations to the biological adjustments that occur within the individual's lifetime (that is, development adaptations and acclimitizations). Most functional adaptations a
Maintenance of Internal Homeostasis
All adaptations have one purpose: maintenance of internal homeostasis, or maintenance of the normal functioning of all organs and physiological systems. To determine how humans maintain internal homeostasis, anthropologists employ indirect approaches and
Homeothermic
Like all other mammals, humans are homeothermic, meaning they maintain a constant body temperature. Humans can tolerate a body temperature higher than their normal 98.6 F, but a body temperature above 104-107 F for an extended period leads to organ failur
Biological Responses to Heat
A body experiencing heat stress attempts to rid itself of internally and externally derived heat sources. Internal heat is produced by the body's metabolism, especially during activities involving movement. External heat is derived form the air temperatur
Bergmann's Rule and Allen's Rule
The relationship between body shape and temperature adaptation was first described in the 1800s by a combination of two biogeographic rules, one developed by the German biologist Carl Bergmann (1814-1865) and the other developed by the American zoologist
Biological Responses to Cold
Severe cold stress is experienced mostly in places close to Earth's magnetic poles, at altitudes higher than 10,000 feet, and during cold spells in temperate settings. Hypothermia, or low body temperature, occurs in excessively cold air or immersion in co
BMR
To measure heat production, anthropologists take a specific kind of measurement called the basal metabolic rate (BMR). Indigenous people living in cold settings have significantly higher BMR than do other human populations.
Skin Reflectance
One of the most profound environmental factors that humans deal with daily is solar radiation, or the sun's energy output, which plays a central role in the evolution and development of skin color. The American anthropologists Nina Jablonski and George Ch
Melanocytes and SPF
When first exposed to UV radiation, light skin reddens�the process commonly called sunburn. With ongoing exposure, the melanocytes increase the number and size of melanin granules. In addition, the outer layer of epidermis thickens. Because melanin is a n
Skin and Vitamin D
The body needs UV radiation for the synthesis of vitamin D, a steroid hormone that regulates calcium absorption and mineralization of the skeleton. UV radiation in the form of UV photons penetrates the skin and is absorbed by a cholesterol-like substance,
Biological Responses to Altitude
At high altitudes, a fall in barometric pressure reduces oxygen molecules. The primary environmental stress in such places is hypoxia, the condition in which body tissues receive insufficient amounts of oxygen. The severity of hypoxia increases as a perso
Energy and Nutrient Requirements
Nutritionists have developed two sets of dietary recommendations: those based on energy requirements and those based on nutrient requirements. Measures in calories, the minimum energy needed to keep a person alive is called the basal metabolic requirement
Consequences of Poor Nutrition
Among the consequences of poor nutrition is the suppression of the immune system. Thus, undernutrition and infection work hand-in-hand. Universally, undernourished populations experience stunted growth, resulting in shortness for age. It is highly unlikel
Obesity
Increasingly around the world, the problem is becoming just the opposite: too much food and too many of the wrong kinds of food. Obesity was mostly unknown in the 1950s, but since the early 1990s it has become a "growing" problem, not only in the US but i
Consequences of the Obesity
As the obesity rates have climbed, so has hypercholesterolemia, or high cholesterol, a predisposing factor for coronary heart disease. Clearly, these changes in consumption are culturally influenced. That is, people learn to eat what they eat. This is an
Type 2 Diabetes in Native American Populations
Is there an adaptive component to the disease? In the early 1960s, the American geneticist James V. Neel noted the high percentages of type 2 diabetes among Native Americans. Neel hypothesized a "thrifty genotype," one that during times of plenty stored e
Bone Homeostasis and Function
Bones' growth and development are subject to a range of factors. Strongly controlled by genes, they are also affected by various physiological processes, disease, and nutrition.
Bone Properties
Various mechanical forces also affect bones' growth and development. The bones of the arms and legs, for example, are subject to bending and torsion, or twisting, whenever they are used. Bones' rigidity, or strength, is a functional adaptation to these fo
Wolff's Law
A principle called Wolff's Law lays out the homeostatic balance of osteoblastic and osteoclastic activity, in which bone mass is produced where it is needed and taken away where it is not needed. Wolff's Law also accounts for the remodeling of bone that o
Bone Density and Workload
At the other end of the spectrum, people who are physically inactive have less dense bones because osteoblasts are not stimulated to produce bone mass. The resulting decline in bone density may weaken the skeleton. Children with less bone mass due to habi
Excessive Activity and Reproductive Ecology
The biological benefits of physical activity are clear. Exercise improves physical fitness by contributing to bone strength, helping lower blood pressure and cholesterol, increasing heart function and lung function, and so on. Exercise that becomes an exc