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Chapter 11

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Sisi Tran

Chapter 11: Physical Health - about 3.6 million years ago Near Laetoli, Tanzania: early hominids, most likely Australopithecus afarensis left foot prints in wet volcanic ash = later became important discoveries in paleoanthropology  viewed as earliest direct evidence of bipedality in hominid line o freed hands to carry food and make tools, cooled body (Reducing amount of direct sunlight that struck body and exposing upper body to wind), and improved long-distance travelling  unlike chimpanzees  big toes didn’t protrude directly off to side, were no parallel prints made by knuckles to support quadrupedal gait, and the footprints revealed that early humans who made them struck w/ heel first and pushed off from toes in same way modern humans do  key transition (ape on all fours to walking on hind legs) in hominid evolution  however still not had been quite as bipedal as modern humans –key differences: wider front part of foot, big toes more separated from second and more pronounced arch; still preserved some key nonhuman characteristics - however, have to consider whose feet one is examining –have to consider that those who left Laetoli footprints had diff cultural traditions compared to modern humans = didn’t wear shoes  figure 11.1: foraging tribe, Machiguenga (don’t wear shoes), are similar shape as Laetoli Austrolopithecines - shape of feet can be seen as cultural product  changes shape of your feet  changes way you run o most of human evolutionary history = wore sandals, minimal thin-soled footwear like moccasins or nothing on feet (running shoe wasn’t invented until 1970s) o however, humans have always been running (without shoes) --?often long distances and rarely reported much damage to feet o run diff on bare feet: land on fore-feet or mid-feet (shoes = land on rear-feet) o figure 11.2: some cultural groups participate in long-distance running w/ bare feet or wearing minimal sandals - thus, cultural exp. shape ways we thin and affect our bodies and our health BIOLOGICAL VARIABILITY OF HUMANS - largely two distinct categories of explanation for this variation 1. there are innate biological diff across cultures 2. there are acquired biological diff Genetic Variation Across Populations - despite our uniqueness we do share genetic variants in common w/ others esp. w/ ppl who share same ancestral origins as us  due to forces from genetic drift and particular selection pressures from geographical and cultural factors (over many generations) affected frequency of particular genetic variants in diff regions of the world - genetic variability among humans < ther species  modern humans (homo sapiens) emerged approx. 100,000-200,000 years ago, and all lived in Africa until approx. 50,000-60,000 years ago  evidence: small population (homo sapiens) quickly expanded before humans left Africa = far less genetic variability across diff races of humans  more genetic variability between Africans than Africans and other cultural backgrounds - skin colour = most salient example… why variation?  most compelling explanation: body’s ability to synthesize vitamin D –necessary for intestines to absorb calcium and phosphorus from food (bone growth and repair) o need shortwave ultraviolet radiation (UVR) to penetrate skin layer and catalyze vitamin D’s production o but, too much can cause breakdown of folic acid (cause anemia or birth defects, or skin cancer) o evolution  Africa = high UVR levels = have enough melanin in skin to allow sufficient UVR to penetrate but not enough to break down folic acid  Moved to other places where UVR levels lower = less melanin = absorb more UVR  Amount of UVR in diff parts of globe correlate w/ skin colour –but there are other explanations that also support link between UVR and vitamin D synthesis o Inuit of Greenland: darker skin but low UVR but eat diet high in vitamin D so don’t require much catalysis from sun o Some ppl from Philippines, Vietnam, and Cambodia have lighter skin than predicted, but just recently migrated from higher latitudes in recent millennia = apparently not yet evolved appropriately darker skin  Example of adaptive response to climate differences among populations geographical factors shaped the genotype o Climate exert strong selective force = individuals better adapted = more surviving offspring o Another selective force: certain kinds of local pathogens = more genetically resistant to pathogens = more likely survive and reproduce (e.g., Spaniards win over Incans, regions of world where HIV infection high = likely develop resistance in as little as 50 years)  Cultural factors shaping the genotype e.g., most adults in world who drink milk develop symptoms of lactose intolerance (not have lactase enzyme in their intestines) o known as lactase nonpersistence: lactase doesn’t persist from childhood through adulthood  Present in ancestral populations of humans before left Africa –sometime after (particularly northern Europe) developed mutation for lactase persistence  Developed in areas where cows domesticated for longest periods (sometime in last 10,000 years, Dairy farming predate this selection), since began to domesticate cattle  Parallel of this genetic mutation: African cultural groups raised cattle distinct from Europe  Brought various nutritional advantages = selection of lactase persistence  Example of cultural horse pulling the genetic cart - growing evidence of strong selective role culture plays on human genome  cultural diff in dietary practices –cultures vary in what they eat = accompanied by genetic evolution that max’s effectiveness of nutrition derive from diets o agricultural societies consume more starch than foraging societies = genetic mutation increases amount of amylase protein in saliva (helps digest starch) o Asians less likely than Europeans to have enzyme that sufficiently detoxifies alcohol = “Asian flush” (p.430) makes drinking less enjoyable = protection against alcoholism  One explanation: moving to large city = challenge of more contaminated water supply Europeans solved this (middle ages) by drinking beer and wine; Asians boiled water and drank tea - indirect influences of culture affecting genome  West Africa Kwa-speaking farmers grow yam crops = increased amount of standing water when rained = habitat for malaria-carrying mosquitoes = evolution of genetic variant for hemoglobin associated w/ sickle-cell anemia = more resistant to developing malaria - studies that discussed immigrants and children showing diff pattern of responses compared w/ ppl who live in heritage culture = important because immigrants genetically identical to ppl from heritage culture, but participate in cultural practices of host culture –none of those studies included role of genes in experimental designs, mostly correlational in nature - # of large-scale international research projects mapping frequencies of diff gene variants –identified several associated w/ psychological variables differing in frequencies around the world  e.g., predict enhanced social sensitivity (5-HTTLPR, A118G, and MAOA), more common in Asian samples than European… may underlie collectivism  may provide sold genetic evidence for cultural diff described in this text –but note relations between genes and psychological outcomes are highly complex (e.g., three genes expressed diff depending on ppl’s exp.) and most conducted in the West - because findings based on Western data = commonly find opposite effects of genes across cultures (examples on p.432)  but even if gene frequencies vary across cultures, doesn’t mean associated psychological traits also vary in same way Acquired Physical Variation Across Cultures - example of Moken developing underwater visual acuity (children more than twice acuity than European children) – developed through regularly participating in cultural practices of diving for food (p.433) O BESITY AND D IE. - compare culture by using standard definition of have obesity of body mass index (BMI) score of at least 30 = tremendous variability in obesity rates around world –figure 11.4: range from approx. 1.5% Chinese women to 55% Samoan women - although there’s evidence for genetic factors predicting body weight and possible certain weight-relevant genes more in one culture than other, culture clearly plays important role  figure 11.5: past few decades = obesity rates risen dramatically across world during past few decades (particularly U.S. and United Kingdom), not genes because no influx into these countries of ppl carrying overweight genes o key reasons = greater reliance on high-calorie foods, larger portion sizes, less active lifestyle as engaging more sedentary activities (internet and playing computer games), and more suburban lifestyle = more driving - large discrepancies between nations in obesity rates, even w/in west  “French paradox”: food rich in delicious yet fat- and sugar-heavy products (cream, butter, pastries, and chocolate) o higher blood cholesterol lvls than Americans o but have longer life span, thinner, and lower heart disease rates than Americans  possibilities for this paradox o French drink more win than Americans = inhibits platelet reactivity = reduces risk of coronary heart disease o Paul Rozin and colleagues alternative: French live in diff cultural environments that affect sizes of portions and attitudes toward food = eat significantly fewer calories per days than Americans  Amount of food ppl eat determined by what’s put in front of them or size of individual portions of food sold in stores  yogurt containers 80% bigger in U.S. than France, foods sold in individual servings (i.e., chocolate bars, soft drinks) larger in U.S.  food in international chain restaurants varies: medium french fries in U.S. have 70% more fries in U.S. than France  chicken McNuggets same = suggest internationally shipped  grilled chicken sandwich bigger in U.S. than France = suggest grilled use diff part of chicken and thus chickens bigger in U.S.  Large portions product of fairy recent cultural evolution  example of starbucks: since it opened in 1971, started increasing their sizes because realized Americans prefer large servings (started w/ short, 8-ounce) 12-ounce (tall), 16-ounce (grande), 20- ounce (venti), 2011=31-ounce (trenti)  portion sizes 2-5 times larger than when first introduced o Rozin and colleagues highlight difference in attitudes toward food  French: view eating as more leisurely and enjoyable activity than Americans; spend more time eating (approx. 50% longer than Americans)  Expected to savor food in France  Response to question (p.437): approx. 80% French choose good food, compared w/ 40% Americans - Americans seem to have conflicted attitudes toward food, esp. women  Americans = effort to eat products altered to make them healthier (less salt, fat, or sugar) compared to French o 80% American females eat products w/ fat removed few times a week, only 20% of French males do this o however, only 35% of Americans claim to be healthy eaters, and 75% of French o first word come to mind when think of “food” American females = “fattening”, didn’t appear on French lists o American college students survey: 14% females embarrassed to buy a chocolate bar o Figure 11.6: Chernoff figures  Average responses of participants in each culture and sex (French, Americans, Japanese, and Belgians)  Each element of face tied to response of particular question about food –more negative = small and unhappy face  Women have more negative attitudes about food than men, American women esp. negative  Males in all cultures fairly positive, esp. French and Belgians CULTURE AND H EIGHT. - shared dietary habits have impact on average height of ppl in a culture –Dutch (Netherlands) are tallest ppl on average on the planet - tend to think genetic factors responsible (basketball team have taller parents) –key role in explaining height diff w/in particular culture, but less useful for between cultures and across historical periods  American men were approx. 3 inches taller than average Dutch men in 1865 (data from military records) o Late 19 century = Americans among tallest due to advantage in income (GNP per capita third highest in the world) th o at same time = Dutch economy going through economic slump, didn’t recover until second half of 19 century = height increased as income increased (continue to this day) - reasons for link between wealth and height  wealth brings healthier diet, esp. in ages w/ growth spurts (infancy and adolescence) = get more vitamins and nutrients  aspects of diets in cultures Japanese height increased 5 inches after WWII w/ increase in milk and meat consumption  average heights coincide w/ broad societal changes that impacted diet (fluctuated over time, not steadily grown) height of Europeans shrink during Industrial revolution (move into cities, populations swelled, average caloric intake dropped in many places) - average height of Americans largely stopped growing taller, but areas in much of rest of the world continue growing as incomes improve; other industrialized countries (not including U.S.) = ppl tend to be taller than parents some explanations  eating habits of American teens
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