Samoa - Anthropology

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
1
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
2
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
3
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
4
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
5
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
6
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
7
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
8
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
9
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)
10
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
11
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
12