HUMAN VARIATION ANTH 105
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Date Created: 10/22/15
Human Responses to the Environment Levels of Response to Environmental Change A Genetic Responses 1 Occur at the population level through natural selection 2 Genetic responses take a long time to institute generations and are difficult to reverse 3 Examples the evolution of bipedalism and larger brains in our early ancestors through natural selection B Developmental Responses Developmental Plasticity 1 Developmental responses occur in individuals during the 2 childhood period of rapid growth 3 Developmental responses usually require a number of years to institute and are difficult or impossible to reverse 4 Example Reduced body size adults who had inadequate childhood nutrition C Acclimatization l Shortterm reversible physiological responses to changes in environmental conditions 2 Example tanning in response to exposure to sunlight D Cultural Responses 1 Responses to the environment based on learning new patterns of behavior or technology 2 Cultural responses can be instituted rapidly and are also comparatively easy to reverse 3 Example The development of clothing by our ancestors Responses to Cold Environments A Immediate responses 1 Vasoconstriction to reduce heat loss 2 Increased heat production through shivering and activity B Developmental Responses increased non shivering thermogenesis C Population Differences 1 Responses to Moderate Cold Australian aborigines Reduced blood ow to extremities and reduced metabolic heat production to conserve energy 2 Responses to Extreme Cold Eskimos Increased metabolic rate and blood ow to the extremities to prevent frostbite Responses to Heat Stress A Responses to High Temperatures B Mechanisms of heat transfer 1 Radiation conduction convection and evaporation 2 Sweating 560 calories lost per gram of sweat C Immediate responses to increase heat loss 1 Low vasodilation 2 Inefficient sweating D Long term responses 1 Increased vasodilation 2 Better distribution of sweat 3 Decreased concentration of salt in sweat E Developmental Responses Children who develop in conditions of heat stress tend to have smaller trunk size and longer limbs of smaller girth than controls F Population Differences 1 Most difference can be explained in terms of developmental plasticity 2 The long limbs of some people who live under heat stress may be explained as genetic adaptations for more ef cient heat loss ie Allen s rule G Evolution of Human Heat Regulation 1 Why are humans such hairless sweaty thirsty animals 2 We thermoregulate through sweating 3 Sweating is efficient only in environments with a low relative humidity so that evaporation occurs 4 Humans have comparatively little capacity to store up water 5 These facts suggest that we evolved our hairlessness in a warm environment with a low relative humidity and plenty of water 6 This is consistent with paleoenvironmental evidence concerning the African environments our early ancestors evolved in 7 Responses to High Altitudes A Immediate Responses 1 Increased rate and depth of pulmonary ventilation 2 Mountain sickness in response to hypoxia B Acclimatization Responses 1 Increase in hemoglobin content of blood 2 Increase in capillarization of the lungs C Developmental Responses found in Native Highlanders 1 Increased lung volume barrel chests 2 Increased pulmonary diffusion capacity D Reproductive Consequence of Life at High Altitudes 1 Reduced sperm production 2 Increased placenta weight Human Responses to Variation in Nutrition A Responses to malnutrition l Stunted growth 2 Reduced metabolic rate Minimum daily requirements and developmental plasticity in nutritional requirements Milk dependence and the geographical distribution of lactase de ciency Variation in Body Form Why Study Body Form A Knowledge of variation in body form is essential for the design of automobiles clothing etc B People have long been interested in the possibility of predicting disease susceptibility behavior etc based on the analysis of body form Early Attempts to Correlate Body From With Behavior A Phrenology 1 A Pseudoscience popular in the 19th century 2 Based on the idea that skull shape re ected brain function 3 Dolichocephalic long headed people were believed by some to be superior to brachhycephalic round headed people B Cesare Lombroso 1836 1909 1 Believed that criminals exhibited degenerate physical features as asymmetrical skulls which allowed them to be identi ed 2 Considered noncriminals who exhibited these features to be quotcryptocriminalsquot C Frans Boas 1 Showed that the shape of the skulls of parents born in Europe were different from those of their children who were born in the United states 2 He attributed this to cultural practices such as swaddling Somatology Classification of the human physique A Sheldon39s system for the classi cation of body shape 1 Endomorphs fat broad from front to back 2 Mesomorphs muscle and bone predominate thin from front to back 3 Ectomorphs thin people B Problems with Sheldon39s work Subjectivity and the quothaloquot effect C Correlations between physique behavior and disease 1 Pulmonary tuberculosis higher in ectomorphy 2 Coronary thrombosis higher in endomorphs 3 Schizophrenia higher in ectomorphy 4 Paranoids higher in mesomorphy Natural Selection Explanations for Variation in Body Form A Bergmann s rule The members of widely distributed species tend to have a larger body size in the colder areas of their range 1 Heat conductance depends on the surface area of the body 2 With increase in body size volume increases at a faster rate X3 than surface area X2 VI VH B Allen s rule The appendages of widely distributed species tend to be shorter in individuals that inhabit the colder areas of their range 1 longer appendages increase the surface area available for heat radiation 2 Developmental plasticity may explain some variation in limb proportions C Explanations of the Pygmy39s small stature l A response to an inadequate food supply 2 An adaptation to hunting in a dense forest 3 Obesity Is the modern human tendency toward obesity a result of the adaptation of our ancestors to a quotfeast and faminequot cycle in food availability D Facial Morphology 1 Is Mongoloid north Asian facial morphology an adaptation for reducing heat loss 2 Narrow European noses an air warming mechanism 3 Were Neanderthals cold adapted Developmental Plasticity as an Explanations for Variation in Body Form A quotBarrel chestsquot in native Highlanders increase lung capacity B Reduced body size in response to malnutrition Is it adaptive C Secular trends in body size Why are we getting bigger 1 Better nutrition 2 Medical care 3 Effects of social stimulation on hormone levels Cultural Modi cation of Body Form A Modi cation of the body for social purposes Cranial Deformation foot binding genital modi cation piercing plastic surgery and body building B Explanations for Body Modi cation 1 Explanations commonly given by individuals beauty self expression and personal symbolism social pressure 2 Sociological explanations status differentiation maintaining social boundaries Why don39t we like our bodies A Cultural stereotypes and biological reality B The marketing of unrealistic body images through advertising increases sales Variation in Human Skin Color and Hair Form Anatomy of the Skin A Epidermis stratum corneum stratum lucidum stratum granulosum carries melanin stratum germanitivum produces melanin B Dermis Contains sweat glands apocrine and eccrine sebaceous glands hair follicles capillaries Sources of skin color A Stratum corneum buildup of dead keratin interspersed in some cases with brokendown hemoglobin and melanin B Blood in capillaries of the dermis C Melanin in the stratum granulosum D Genetic studies suggest that a small number of genes determine skin color Developmental Plasticity and Acclimatization A Girls have lighter skin than boys B Skin color darkens with age C Effects of diet certain foods can in uence skin color D Tanning as an adaptive response to ultraviolet light Geographical variation in skin color A Skin color is usually measured through color matching and re ectivity B Although there are many exceptions throughout the world darker skinned people tend to inhabit areas nearer the equator Possible explanations of geographical variation in skin color A Skin Color and heat exchange 1 Dark skin absorbs more radiant energy than light skin 2 Heat absorbed by dark skin may be an adaptation for replacing body heat lost during the night 3 This has the disadvantage of increasing heat load B Skin Color and Frostbite Susceptibility 1 Dark skin may be more susceptible to cold injury than light skin 2 In areas where frostbite is a problem light skin would have a selective advantage C Radiation protection 1 Ultraviolet light is known to be harmful if it penetrates the skin It causes sunburn and may induce cancer 2 Darker skinned people have an advantage when exposed to high levels of ultraviolet light 3 The late onset of skin cancer may reduce its significance as a selective pressure D Skin Color and Vitamin D Synthesis 1 Vitamin D is synthesized in the epidermis through the action of ultraviolet light on a steroid precursor 2 Low levels of Vitamin D produce rickets and skeletal malformations that can result in death during childbirth 3 Too much Vitamin D results in kidney stones and calcification of soft tissues 4 As people moved from the tropics to temperate areas reduced sunlight and the necessity of wearing clothes would select for depigmentation to regulate vitamin D synthesis VI Cultural Modi cation of Skin Color A Tattooing Scari cation Branding Body Painting B Functions tribal identi cation beauti cation stigmatization VH Hair A Does natural selection explain population differences Head hair as protection B Sexual Selection Darwin believed that sexual selection explained the relative hairlessness of humans as well as population differences Is hair a signal of health status C Social Function of Hair 1 Pubic hair axillary hair apocrine glands and body odor Why are we so concerned about our smell 2 Hair styles as tribal marks VI VH Human Sexual Dimorphism The difference between gender and sex A A person s sex is their biological identity B A person s gender is their sociocultural identity The genetic and hormonal basis of human sexual dimorphism A The genetic basis of sex differences xx and xy are typical genotypes but there are many variations xyy xxy xxx xo etc B Androgens r quot 39 for diff quot quot of sex phenotype during fetal development Later causes for muscular development laryngeal development balding acne C Estrogens estrogen progesterone relaxin estrogen stimulates development of female secondary sexual characteristics at puberty progesterone is important in regulating ovulation and the menstruation relaxin is important at the time of birth D Overlapping distributions of sex hormones in men and women Sex differences in human morphology and physiology Men are about 10 lager than women and have longer legs relative to the trunk Men have a higher proportions of bone and muscle and women more fat Men have higher concentrations of hemoglobin than women Women have a lower basal metabolic rate than men Women have a more quotactivequot immune response than men Some sex differences hip width shoulder width are a result of androgen and estrogen stimulation of specific cartilage cells The evolution of sex TUP39JUOW A Advantages of Asexual Reproduction Allows rapid reproduction no energy expended in finding a mate offspring receive all of parents genes B Sexual reproduction Considerable time and energy expended in finding a mate offspring receive 12 of parents genetic compliment C Advantages of Sexual Reproduction Allows increased genetic variability through crossing over John Tooby39s theory the variability that results provides a moving target for pathogens Natural selection as a cause of human sexual dimorphism A Hip Width and reproductive success Why do men have such narrow hips B Subcutaneous fat and Energy Storage Did the capacity for energy storage increase the reproductive success of early human females Sexual selection as a cause of sexual dimorphism A Are the breasts and buttocks of women an advertisement of reproductive potential B The spearman and the archer Wide shoulders and weapons technology Is there a feedback between technology natural selection and sexual selection C Balding Beards and Bluff D Are population differences in face form simply a re ection of differences in sexual preferences Sexual dimorphism and mating systems A Polygamy tends to be associated with a great deal of sexual dimorphism Examples elephant seals and baboons VHI XI XII XIH B Monogamy and a lack sexual dimorphism eg Gibbons C Femalemale weight ratios of apes Gibbons 10393 Orangutan 49 Gorilla 48 Chimpanzee 88 Human 89 D Analogies with early human mating systems Developmental explanations of sex differences A The magnitude of adult sexual dimorphism is in uenced by the conditions a person is exposed to during development B Genetic males can become phenotypically female and Vise versa if exposed to certain chemicals at critical times during their development C Sensitive Males the development of males is more sensitive to environmental variation than is that of females This can result in a reduction in sexual dimorphism during unfavorable periods Acclimatization hormone levels and reproduction A Malnutrition stress and lowered testosterone levels B Malnutrition low body fat and infertility in women Culture as an explanation of sex differences A sex refers to a person39s biological identity gender refers to a person s cultural identity B Cultural in uences can increase or decrease sex differences C Cultural practices that accentuate sex differences in morphology Fashions foot binding lip stretching weight lifting and plastic surgery D Reinforcement of gender roles during socialization Sex Differences in Behavior A Nonhuman examples progesterone stimulates nest building behavior in rodents and parental behavior of both male and female birds B Primate experiments sex differences in quotrough and tumble playquot and grooming in surrogate raised androgenized monkeys C The prenatal hormonal environment in uences later behavior Sex differences in cognition A There is much overlap in male and female performance on tests of cognitive ability B Women tend to perform better than men on tests of verbal ability perceptual speed tasks that require fine motor coordination mathematical calculation tests C Men tend to perform better than women on tests of certain spatial abilities target directed motor skills and tests of mathematical reasoning D Before puberty few consistent sex difference are apparent E Testosterone levels are know to affect performance on certain tests F There is disagreement over the extent to which these differences are a result of differences in biology or di erences in socialization lifestyle etc Gender Differences A Similarities have been found in the anterior hypothalamus of some homosexual men and women B Some tests show homosexual men to be similar to women in their performance on certain tests C There is disagreement over the extent to which these differences are a result of differences in biology or differences in socialization lifestyle etc Intelligence and Intelligence Testing I What is intelligence A One intelligence Several types of intelligence Intelligence is what intelligence tests measure B Intelligence as a species speci c way of adapting each organisms nervous system has been designed by natural selection to solve specific problems relevant to its survival C An adaptive de nition human intelligence intellectual capacities valuable to our early ancestors include memory as well as the capacity to symbolize and generalize II Cultural differences in sensory processing and patterning A Perception as a focusing of sensory input so that there is selective awareness of the surroundings B Children learn to perceive the patterns and con gurations in their surroundings according positive and negative reinforcements provided other members of their culture HI Population differences in susceptibility to Visual illusions and skill at solving embedded gure problems A The effects of living in a quotcalpenteredquot world B quotLinearquot and quotnonlinearquot thinking C Differences in quot eld dependencequot D Effects of the environment on development of the nervous system and cognitive abilities IV Sensory enrichment and sensory deprivation A The malnourished mind B Industrial pollutants the effects of lead as an example V Intelligence Tests A Cultural biases in IQ tests B Heritability of IQ studies of heritability are based on the idea that variation in phenotype Vp variation in genotype Vg variation in environment Ve C Studies designed to measure the heritability of IQ involve either attempting to control for the environmental or genetic variable D Measures of heritability describe the degree of variance in a population which is due to genes under a speci c set of environmental conditions E What do SAT39s predict F Intelligence tests an autonomous force of cultural selection G Intelligence tests as tools Human Variation In the Future 1 II diseases Genetic Engineering We know that we will be a lot better at identifying genes associated with A Example Women with the BRCA1 gene have 85 increased risk of developing breast cancer and a 45 risk of ovarian cancer Preventative surgery What will we do with genetic information A It will be used to make money Hundred of millions are at stake B Should genetic sequences be private property C Information on genetic disorders that cannot be treated poses psychological problems Should children at risk be tested I D Should people be tested if their is no treatment What effect will this knowledge have on the human gene pool A It seems clear that in the near future these techniques will only be available to the wealthy B 122 million children lt5 died in the developing world in 1993 95 of these deaths were from preventable diseases Gene therapies are certaintly not the best way to deal with the health problems of most of humanity C The Rurla Advancement Foundation opposes patents on living things A patent was granted to NIH on a sequ3nce from a Papua New Guinea man Genetic discrimination A 455 of 917 with genetic diseases repo41ted having been discriminated against by insurance companies B 22 of the members of a family some of whose members have a genetic disease report being discriminated against by insurance companies Final Study Questions Marks Chapter 9 1 What is the signi cance of geographical gradients and cultural boundaries in de ning human races Can we use them to represent fundamental biological divisions among different peoples 2 What are the two major forms of genetic polymorphic variants found in the human species 3 Discuss some of the problems of trying to genetically test in order to classify them into groups on the basis of a phenotype like skin color 4 Explain what the quotOut of Africaquot hypothesis is and how mtDNA studies have been used to support this theory 5 What is the Human Genome Project and what are its objectives Be able to discuss the strengths and weaknesses ofthe project Marks Chapter 10 How do differences or gradients arise in human populations Why is adaptation a troublesome concept in evolution What are the four different processes that can be defined as adaptation In what two ways can structures arise that are not necessarily adaptive What is the quotpathology paradigmquot What was T Dobzhansky 39 s quotbalancequot model Explain Allen39s rule Bergmann s rule and Gloger s rule What is the quotthrifty genotypequot hypothesis Explain how cultural adaptation can result in behavior that does not maximize reproduction M rks Chapter 11 1 What are the two major demographic transitions that Marks identifies Explain their consequences for social structure population etc 2 In America are differences in fertility due to issues of race or economics Explain 3 What consequences does an agrarian life have on disease nutrition and labor 4 What are some of the problems of cultural solutions to health problems Marks Chapter 12 1 Why is it dangerous to correlate some of our behaviors such as warfare and rape to animals who also exhibit them To what extent can we say these behaviors are homologous across species 2 What does AJ Bateman have to say about male and female reproductive variance 3 What is the difference between proximate and ultimate causes in biology 4 Discuss the four fallacies in F Goodwin39s argument on promoting violence from an evolutionary scientifrc perspective 5 Explain quotheritagequot plesiomorphies and quothabitusquot apomorphies Include WK Gregory39s discussion these terms Marks Chapter 13 1 What are the three types of population comparisons that Marks discusses 2 How do social and historical factors in uence an individual s performance ie sports behavior 3 Discuss the role of genetics and environment on intelligence aggression and sexuality OWSQM eP Nf