Evolutionary Psychology

Evolved Mechanisms

• ALL psychological theories imply evolved psychological mechanisms– Where did these mechanisms come from?– Why do they exist?

• They evolved to solve recurrent adaptive problems in our ancestors!

• Evolution by natural selection is the only viable answer

• Ultimate explanations

Evolved Mechanisms

• What are the characteristics of evolved psychological mechanisms?– Blind design (not made from scratch)– Gene selection: selfish genes– Domain specificity

• Swiss army knife

– May emerge at any point in development; need not be present at birth

Environmental Input

• Is evolutionary psychology genetic determinism? – NO

• All evolved psychological mechanisms are dependent upon environmental input– Internal or external

• Even biological/genetic physiological adaptations such as muscles require input (nutrition and exercise) to develop and maintain– Psychological mechanisms are no different

(language)

Evolved Mechanisms

What about culture?

• Culture is often used as an explanation for human behavior and differences between individuals and groups

• But culture is not an explanation for anything – it requires an explanation!

• The existence of culture requires evolved psychological mechanisms

• Cultural differences are the result of varied environmental input– Availability and type of resources– Population density– Male to female ratio– Presence of geographic barriers/isolation

Sex Differences

• Males and females have faced some separate adaptive problems throughout our species’ history due to both biological conditions (reproduction) and social conditions (gender roles)

Sex Differences

• Males: hunting → greater upper body strength and greater spatial rotation ability for throwing spears

• Females: gathering → better spatial location memory for finding and remembering good food sources

Sex Differences

• Males: tribal warfare, group hunting → strong coalitional tendencies

• Females: patrilocal societies → weak coalitional tendencies

Sex Differences in Mating

• Males: paternity uncertainty → sexual jealousy

• Females: need for resource investment for children → emotional jealousy

Sex Differences in Mating

• Males: cryptic ovulation → long term relationship with frequent sex

• Females: dual male strategy of long term and short term mating → discerning whether a male views her as a long term or short term mate

Important Findings of EP

• Altruism and kin selection• Why are we nice (self-sacrificing) to

each other if genes are “selfish?”– We are most likely to exhibit kindness

to people who share our genes– Reciprocal altruism with friends has

benefits (i.e., can be selfish)– Altruism can raise social status and

attract mates

The Wason Selection Task

Each card has a number on one side and a letter on the other. Indicate which cards you need to turn over to see if any violate the following rule: If a card has a D on one side, it has a 3 on the other.

The Wason Selection Task

Imagine you are a bouncer at a bar. If a person is drinking beer, he must be at least 21 years of age. One side of each card shows a person’s age, and the other side tells what he or she is drinking. Indicate the cards you need to turn over to find out whether anyone is breaking the law and needs to be thrown out of the bar.

Important Findings of EP

• Social exchange/cheater detection• Humans are very good at interpreting

conditional rules of social contracts• Social exchange problems on the

Wason selection task are always solved much more easily than corresponding logic problems

• This is true even if the social contract is unfamiliar

Which figure is most attractive?

Important Findings of EP

• Universal preference and importance of waist-to-hip ratio in females– Fertile women .67-.80– Lower is better– Average preference in all cultures surveyed = .70 (range

= .68 to .72)– Average actual WHR among females in the United States

= .80

• Honest signal of health and fertility– Greater fertility– Reduced risk of cardiovascular disease– Reduced risk of diabetes– Reduced risk of at least 7 different types of cancers– Reduced risk of cognitive impairment

What does it all mean?

• Humans are adaptation executors, NOT fitness maximizers!

• “Mean genes”

Recommended Reading

• Evolutionary Biology– The Selfish Gene by Richard Dawkins– The Blind Watchmaker by Richard Dawkins– The Ancestor’s Tale by Richard Dawkins

• Gene/Environment Interactions– Nature via Nurture by Matt Ridley

• Recent Human Evolution– Before the Dawn by Nicholas Wade

• Evolutionary Psychology– The Evolution of Desire by David Buss– Survival of the Prettiest by Nancy Etcoff– Sperm Wars by Robin Baker– The Dangerous Passion by David Buss– The Murderer Next Door by David Buss– Mean Genes by Terry Burnham & Jay Phelan