Samoa - UA Anthropology

Samoa - UA Anthropology

Lessons from the South Pacific: The Samoan Studies Project by Jim Bindon, PhD Department of Anthropology University of Alabama Why Samoa? vISLAND SET...

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Lessons from the South Pacific: The Samoan Studies Project by Jim Bindon, PhD Department of Anthropology University of Alabama

Why Samoa? vISLAND SETTING ENSURES POPULATION BOUNDARIES vWELL KNOWN POPULATION ETHNOGRAPHICALLY, ECOLOGICALLY vHISTORICAL CHANGES IN POPULATION IN PAST 50 YEARS PROVIDE A “ NATURAL EXPERIMENT”

The Samoan Studies Project vFormulated in 1974 to investigate the biological consequences of modernization among Samoans vFirst fieldwork conducted among Samoan migrants to Hawaii, 1975 vSubsequent fieldwork done in Western Samoa, American Samoa, Hawaii, and California

Perception

Stress

Fight or Flight Cerebral Cortex ACTH

ADRENAL CORTEX Glucocorticoids: Cortisol Increase: Blood sugar Triglycerides Fatty Acid Mobilization Decrease: Glucose clearance Inhibit: Insulin Action

Hypothalamus

Sympathetic Stimulation

ADRENAL MEDULLA Catecholamines: Epinephrine Norepinephrine Increase: Heart Rate Stroke Volume Arterial Vasoconstriction Clotting Factors Blood Pressure

Basic Principles v Adaptation to the environment by natural selection • Population gene pool is molded by past events which shape natural selection • "Thrifty Genotype Model"

v Social influences on human biology • Behavior and its cultural context affects health • Modernization changes patterns of health and disease, especially through chronic stress

Aver age Systolic Blood Pr essur e of Adults (Modified fr om Waldr on et al. 1982)

139

Industrialized

127

Agricultur alists

116

Hunter/Gatherer

110

120

130

140

Systolic Blood Pressure, mmHg

Evolutionarily our bodies are not adapted to an age related blood pressure increase

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Diabetes Rates among Adults of Various Populations

Thrifty Genotype (TG) Model

Nauru, Micronesia Pim a Indians Mississippi Choctaw Funafuti, Micronesia Urban Asian Indians U.S. Black U.S. White Taiwan 0

10

20

30

40

50

v Neel (1962) noted that Type II diabetes was unequally distributed across human populations v He reasoned that the populations with the highest diabetes prevalence were likely to have undergone cyclic episodes of severe resource deprivation v He postulated a model of natural selection favoring energetic efficiency for these populations

Percent with Type II Diabetes

Feast and Famine Intake

Thrifty Genotype in Feast

Expenditure

v High caloric intake, relatively low activity expenditure v TG individuals more efficient at handling excess calories due to hyperinsulinemia

Aver age Kcal/per son/day

4000 3000 2000 1000 0 Winter Spring Summer

Fall

Winter

Spring Summer

Thrifty Genotype in Famine vLow caloric intake, relatively higher activity expenditure vTG individuals have higher energy stores in adipose tissue to draw on to meet needs vNegative effects of TG such as reduced insulin sensitivity in peripheral cells and excess adiposity are counteracted by reduced caloric availability

Fall

• Circulating insulin activates lipoprotein lipase on the capillary surfaces which hydrolyzes triglycerides in the plasma to facilitate transfer into adipose cells • Insulin also inhibits hormone sensitive lipase which is instrumental in hydrolyzing triglycerides stored in adipose tissue and releasing fatty acids into plasma • Leaves them better adapted to undergo subsequent deprivation and cold stress

Thrifty Genotype in Energy Balance vModerate to high caloric intake and expenditure vNo excess energy to process • TG individuals not at a selective advantage or disadvantage

vHigh levels of activity normal for prepremodern societies counteract insulin resistance in peripheral tissues

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Thrifty Genotype in Small Chronic Excess v Low to moderate caloric intake and expenditure • Intake exceeding expenditure by as little as 10 Kcal/day or one bite of apple

v TG individuals efficiently process excess calories due to chronic hyperinsulinemia • Predisposed to obesity (lipogenesis) • Type II diabetes (insulin resistance) • Cardiovascular diseases (hypertension)

Pacific Islands

m i g E ar l y l an r a t e d P o l y n din g 3 w es t e s i a n s ,00 f 0+ r o m y ea A s i a rs ag o

Shifts in the Adaptive Landscape v3,000 - 5,000 years ago: Voyaging to settle the islands of Polynesia • Selection for thrifty genotype

v30 - 50 years ago: Modernization changes lifestyle, behavior • Thrifty genotype becomes detrimental as it predisposes to obesity, diabetes, cardiovascular diseases

The South Pacific Sailing Barrier between Near Oceania and Remote Oceania

About 2500 miles from Honolulu to Pago Pago

Samoa

About 1500 miles from Auckland to Pago Pago

Near vs. Remote Oceania Near Oceania vNear Oceania is settled before 10,000 years ago • It is a Pleistocene outpost • People were sailing the < 100 miles from Sunda (Island Southeast Asia) to Sahul (Australia, Tasmania, New Guinea) over 40,000 years ago • Distance from New Guinea to the Solomons is less than that, even today with higher sea level

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Summer Currents Lapita Peoples vAround 5,000 years ago a new marine adapted population sailed along the coastline, reaching the eastern end of Near Oceania by 3,500 years ago vThese Lapita people brought with them tree and root crop agriculture and intensive marine exploitation vNo voyage is more than a one day trip under favorable wind conditions

Summer Winds 500 Miles of Ocean vWhen the Lapita people reached the end of the Solomons, Solomons, they faced a 500 mile open ocean voyage where the prevailing winds and currents were against them

Sailing and Paddling Exploration v They began experimenting sailing into the wind • They improved the design of their canoes

v If they sailed out for several days and failed to find landfall, they would turn and speed with the wind at their back to return home • If the return wind failed them they would paddle

v They also perfected a preservation technique that allowed them to carry food with them in case the adventure was prolonged

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What they were looking for

Stresses of Exploration v Dietary stress: • Energy in general and carbohydrates in particular may be in low supply

v Work stress: • Paddling the canoes becomes important only when survival is threatened and the boat had to move to reach safety

v Cold Stress: • Low, open platforms with wet bodies and wind chill would induce substantial cold stress, particularly at night time

Survival of the Fattest

Stress

Cold

T h r i f t y

Diet

G e n e s

Work v Broad body for paddling and heat retention v Insulation from cold especially in voyaging canoes v Storage of energy for period of limited food availability v Glucose sparing for high fat and protein, low carbohydrate diet v Selection maintained by periodic storms and famine

Response I G F 2

I N S

Result

↑ Muscle Growth

Strong limbs for paddling

↑ Skeletal Growth

Low surface area to mass

↑ Insulin

↑ Fat deposition: Insulate body, store calories

Insulin Resistance

Spare glucose, prevent ketosis

Swidden agriculture Villages built along coastline

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Taro gardens

Coconuts

Reef Resources Deep sea resources

Subsistence Regimen

Pigs

v Breadfruit v Banana v Coconut v Taro v Other cultigens carried on boats

v Birds and Bats v Chickens v Pigs v Dogs v Shellfish and Fish

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Culture Contact and Change in the 19th Century

Missionaries

Partitioning of the Islands

vMissionaries open up Samoan Islands in the 1830s vWhalers and traders use Samoa as a port of call from 1850 on vColonial competition between Germany, Great Britain, and the U.S. starting in the 1880s

Samoan Archipelago

vTreaty signed by the three powers in December 1900 vGermany takes over large islands west of 171 west longitude vThe U.S. controls the small islands east of that line vGreat Britain receives concessions in Tonga and the Solomon Islands

Western Samoa in the 20th Century

Western Samoa

vGermans try to establish plantations vMelanesians imported as workers vNew Zealand Protectorate in 1918 vIndependence in 1962 vMinimal economic development • < 50% of men earn wages • < 15% of women earn wages

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American Samoa in the 20th Century

Pago Pago Bay Area

vNaval base in the Pago Pago Harbor, more G.I.s than Samoans during WW II vNavy withdraws in 1951 causing economic depression, outmigration v"Great Society" accelerates economic development in 1960s • >70% of men earn wages • >30% of women earn wages

Elements of Modernization v Cash economy • Increasing engagement in world economy

Migrants to Hawaii

v Formal education system • Training needs for cultural competence exceeds what the family can give

v Secular governance • Movement away from kin and religion based governance

v Urban units • Significant aggregations of population in size, number, and density

Figure 1. A speculative model model of modernization and thegenotype "thrifty" genotype. A speculative of the thrifty

Modified by Modernization v Diet • Increases dietary stability, calories, calories from fat, salt, • Decreases fiber

v Physical activity

Traditional Society Properties

Dietary Uncertainty

Modernized Society Properties

Moderate to High Physical Activity

Dietary Stability

Reduced Physical Activity

Small Chronic Caloric Excess

Insulin Resistance of Muscle Cells

Thrifty Genotype

Feast, Famine, and Caloric Balance

Insulin Sensitivity of Muscle Cells

• Decreases energy expenditure in work and leisure activity

Hyperinsulinemia

v Psychosocial stress • Increases stress in a variety of ways

Maximum Metabolic Efficiency

Reproductive Advantage

Obesity and Beta Cell Exhaustion

Diabetes and Sequelae

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Weigh and Measure

Percent Obese

Prevalence of Obesity among Samoan Adults 100 80 60 40 20 0

76.0 52.6

67.7

74.1

28.6

Western Sam oa

Men

Am erican Sam oa

Hawaii

Women

Prevalence of Diabetes among Samoan Adults Percent Diabetic

Check for Diabetes

58.0

30

27.2 20.6

20 10 4.0

0

18.0 9.0

5.5

Western Sam oa

Men

Am erican Sam oa

San Francisco

Women

Prevalence of Hypertension in Samoan Adults 40 32.7 Percent Hypertensive

Measure Blood Pressure

30

27.7 22.7

20 10 0

13.4 7.9

6.4

Western Sam oa

Men

Am erican Sam oa

Hawaii

Women

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Modernization and Health

Genes

vNonlinear association between modern lifestyle and health vThreshold model, lifestyle in American Samoa sufficient to trigger obesity, diabetes, hypertension vMore modern settings like Hawaii and California permit better adaptation to modernization

vApolipoprotein E*4 relative to Apo E*3 is associated with: • Lower weight, Body Mass Index, and arm circumference • Lower percent glycated hemoglobin • Lower systolic blood pressure • Sources: Crews et al. (1991); Crews (1994)

Diet vDiet shows no association with

Assess Diet

Evaluate Activity

• obesity • blood sugar levels • blood pressure

vTotal calories, calories from fat, total fat, total fiber, salt intakes and types of foods consumed found not to be associated with any of the health outcomes (Bindon 1982; 1984; 1988)

Activity vActivity is associated with obesity but not blood sugar or blood pressure • More active Samoans are less likely to be obese (Bindon 1982; 1994) • Activity is not associated with blood sugar or blood pressure (Knight 1993)

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Association of Obesity and Activity 100 76

Percent

80 60

Measure Stress

60 40

40

24

20 0

Not Obese

Obese

Fatness Level Low Activity

High Activity

b) Diastolic Blood Pressure

Psychosocial Stress

• Younger (< 54 years) Samoan men with incongruous lifestyles have higher blood sugar and higher blood pressure than older men (Bindon et al. 1991; Bindon et al. 1994)

a) Systolic Blood Pressure 180 170 mm Hg

160

100 mm Hg

vPsychosocial stress is associated with blood sugar and blood pressure but not obesity-but there are intracultural obesity--but dimensions of variability

110

90 80 70

Low LSI Young Males

Young Females

Old Males

Old Females

Logistic regression coefficients on Blood Sugar Variable

150 140

High LSI

Minutes since food

Coefficient -0.003

130

Lifestyle Incongruity

120 110

Low LSI

High LSI

0.506*

*p < 0.05; N = 30 adult male Samoans

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tSamoan women do not show the same lifestylelifestyle-outcome associations as do Samoan men (Bindon et al. 1994; Knight 1993) tIn fact, the phenomena that are associated with higher blood pressure among the men are associated with lower blood pressure among the women

Systolic Blood Pressure, mm Hg

154

Psychosocial Str ess

152

Males

150 148 146 Females

144 142 140 138

Low

High

Life Style Incongruity

A Multidimensional Model of Disease Risk for Samoans

Systolic Blood Pressure, mm Hg

160

155 Males

Thrifty Thrifty Genotype Genotype

150

Females

140

One or Neither Employed

Cardiovascular Cardiovascular Disease Disease

Psychosocial Psychosocial Stress Stress

??

??

145

135

Diet Diet and and Activity Activity

Obesity Obesity

Type Type IIII Diabetes Diabetes

Both Spouses Employed

Household Employment Status

Conclusions JThe relationship between modernization and health is much more complicated than anticipated JImportant to know the history of the population to understand genetic predispositions JLifestyle influences can be expected to operate differently on segments of the population

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