October 7, 2013
The ideal mate
o Older (about 3 1/2 years older)
o Symmetrical face (indicative of health)
o High parental investment
o Youth & health (reproductive potential)
o Symmetrical face
Cooperation and altruism
Cooperation - situations in which one individual helps another and in so doing also gains some
Adaptive advantage clear - groups could accomplish more together than they could alone.
When one individual helps another, but in doing so he or she accrues some sort of cost.
Darwin recognized that ‘altruism’ poses a problem – how can evolutionary theory explain
Explanations for altruism
o Behaviors that help genetic relatives may be favored by natural selection
Having offspring isn’t the only way to ensure your genes are passed to future generations
o Help relatives – who share some of your genes - produce offspring
o A helpful action is repaid at a later date by observers of the helpful individual
o Ex: giving blood. Could your motivation to donate blood have an adaptive basis?
Small cost to the donor, no obvious gain to the donor, big gains to the recipient
Doesn’t make sense from evolutionary perspective
Why help some unrelated person and impose even minor risk to yourself?
o Is there a benefit to the donor?
Maybe the donor is repaid by his everyday companions
o Richard Alexander
Our psychological mechanisms have evolved in ways that make us feel good
when we do conspicuous good deeds Reciprocity hypothesis
1. Unpaid donors should almost always let their friends know they gave
2. People will be reluctant to broadcast their refusal to give blood
3. When people have a choice of other people to help, they’ll prefer to
help those that are known to be generous
Hereditary & Heritability
• Heredity - means the passage of characteristics from parents to offspring by way of genes.
• Heritability - how much of the variation in a characteristic within a population can be attributed
to genetic differences.
• In terms of personality: how much difference in personality exists, can be attributed to
• Take population and look at intelligence across the population, how much variance can
be attributed to genetics
• Are there genetically determined ‘boundaries’ on the expression of a trait?
• Reaction range
• Range of possibilities - upper and lower limits - that the genetic code allows
• Individual inherits a range for potential expression of a trait