Problems of survival (1): Outline
I
Hunter-gatherer life
I
I
I
I
Darwinian medicine
I
I
I
mortality
causes of death
nutrition
senescence
why we get sick
The behavioral immune system
I
I
disgust
group bias (ethnocentrism and xenophobia)
Staying alive: Life as a hunter-gatherer
We evolved as hunter-gatherers. How was life different?
I
higher mortality, different causes of death
I
diet of wild foods
I
little anonymity; small mobile groups
Mortality as a hunter-gatherer
What does an “expectation of life at birth of 32 years” mean ?
Ache mortality
Canada mortality
Mortality as a hunter-gatherer: Causes of death
Differences in causes of death?
I
Infection
I
I
!Kung: infection and parasites 70-80% of deaths; Howell
Trauma
I
Efe:
63% health complaints concerned trauma; Bailey
I
Violence?
I
Ache: cause of death, 15-59 years due to: ((Hill and Hurtado)
I
I
I
I
violence: 46%
illness: 28%
accidents: 23%
degenerative: 3%
The real paleo diet: Good or bad?
(except the hunter-gatherer is walking, not riding)
Hunter-gatherer nutrition
The good:
I
no nutritional deficiencies (mobile, foraging !Kung)
I
↓ sugar, ↓ saturated fat, ↑ fiber
The not-so-good: calorically marginal (!Kung, Ache)
I
costs in illness, work
I
costs in fertility
Hunter-gatherer birth seasonality
more !Kung children conceived in the “fat time” (Ache similar)
Implications for evolutionary psychology
Strong selection for
I
avoiding infection and accidents
I
coping with violence
I
finding calorie-rich foods
Problems of survival (1): Outline
I
Hunter-gatherer life
I
I
I
I
Darwinian medicine
I
I
I
mortality
causes of death
nutrition
senescence
why we get sick
The behavioral immune system
I
I
disgust
group bias (ethnocentrism and xenophobia)
Why do we get sick?
I
trade-offs
I
constraints
I
conflicts
I
defenses
I
smoke-detector theory
I
novel environments
Why do we senesce?
Senescence is the deterioration of the body with age.
late-life effects on reproduction and survival have smaller effects on
Darwinian fitness than at earlier ages.
Evolutionary theories about aging
deleterious alleles that are expressed at older ages can accumulate
through mutation and not be selected out (e.g., Huntington’s)
Antagonistic pleiotropy: (pleiotropy = gene that affects more than
one trait)
I
a gene positive in youth, deleterious when old
I
will selection favor?
I
testosterone in males?
I
tumor suppressor gene p53 ( too much → aging, too little →
cancer)?
Why do we get sick?
I
trade-offs (sickle-cell, senescence. . . )
I
constraints
I
conflicts
I
defenses
I
smoke-detector theory
I
novel environments
Why do we get sick?
I
trade-offs (sickle-cell, senescence. . . )
I
constraints
I
conflicts
I
defenses
I
smoke-detector theory
I
novel environments
Why do we get sick?: Conflicts
Toxoplasmosis
makes rats fearless, especially around
cats!
may affect human behavior also
(by-product)
other examples?
Why do we get sick?
I
trade-offs (senescence, sickle-cell)
I
constraints
I
conflicts (rabies, toxoplasmosis in rats)
I
defenses
I
smoke-detector theory
I
novel environments
Why do we get sick?
I
trade-offs (senescence, sickle-cell)
I
constraints
I
conflicts (rabies, toxoplasmosis in rats)
I
defenses (coughing, fever, iron-poor blood, anxiety,
depression?)
I
smoke-detector theory
I
novel environments
Why do we get sick?
I
trade-offs (senescence, sickle-cell)
I
constraints
I
conflicts (rabies, toxoplasmosis in rats)
I
defenses (coughing, fever, iron-poor blood, anxiety,
depression?)
I
smoke-detector theory
I
novel environments
Why do we get sick?
I
trade-offs (senescence, sickle-cell)
I
constraints
I
conflicts (rabies, toxoplasmosis in rats)
I
defenses (coughing, fever, iron-poor blood, anxiety,
depression?)
I
smoke-detector theory
I
novel environments (diabetes, allergies? SIDS? depression?)
Problems of survival (1): Outline
I
Hunter-gatherer life
I
I
I
I
Darwinian medicine
I
I
I
mortality
causes of death
nutrition
senescence
why we get sick
The behavioral immune system
I
I
disgust
group bias (ethnocentrism and xenophobia)
The behavioral immune system: Disgust
We have an evolved psychology to detect and avoid disease
I
disgust: expression in infants associated with bitter taste
I
generalized later: what do you find disgusting?
I
e.g: feces, rotten food, bodily secretions, signs of illness
I
reduced by exposure, culturally modifiable
disgust face: clenched nostrils,
squinty eyes, pursed lips:
decreases sensory exposure?
The behavioral immune system: disgust and immunity
Exposure to pictures of guns or disease
increased immune marker in white
blood cells (not to threatening stimuli
in general). From Schaller et al. 2010
The behavioral immune system: social bias
Does avoiding outsiders reduces exposure to novel pathogens?
Looked at:
6.50
Nigerian Immigrants
6.25
Scottish Immigrants
6.00
5.75
5.50
5.25
5.00
Accidents
Diseases
Percent Allocation of Funds
Endorsement
1. people who naturally felt more vulnerable to disease (q’aire)
2. people primed to feel vulnerable to disease
65
60
Foreign Immigrants
Familiar Immigrants
55
50
45
40
35
30
Accidents
Salient Threat
Diseases
Salient Threat
Figure2. Interaction between disease salience and geographical origin of immigrants on endorsement of
potential immigration (Study 5).
Figure3. Interaction between disease salience and foreign-ness of geographical areas on allocation of
immigration advertising budget (Study 6).
from Faulkner et al.
The behavioral immune system: social bias
does sensitivity to disease lead to in-group bias? (Maybe)
I
people who feel vulnerable to disease: more in-group bias
I
pregnant women in 1st trimester: more sensitive to disgust
I
pregnant women, 1st trimester: more in-group bias
Fig. 1. Intergroup bias and nausea over the course of pregnancy. The solid
line depicts the relative attraction for the American over the foreign target
across week of pregnancy. The dashed line depicts self-reported nausea.
from Navarrete et al 2007
from Fessler et al 2005
Problems of survival Summary
Hunter-gatherers: threats to survival
I
high infant and child mortality (but normal lifespan)
I
deaths from infection, accidents, aggression (not degenerative
disease)
Darwinian medicine
I
senescence due to lower selection at older ages
I
illness from an evolutionary perspective: defenses, trade-offs,
novel-environments, smoke-detector principle
The behavioral immune system
I
disgust: elicited by things that might make you sick
I
sensitivity to disease may enhance group bias