Evolutionary Psychology
We’re going to discuss two main concepts in this chapter:
1. Altruism and Natural Selection: an evolutionary perspective on human nature
➢ Natural selection and behavior
➢ Altruistic behavior
➢ Inclusive fitness and kinship
➢ Reciprocal altruism
2. Sexual Selection and Sex differences in Behavior: an evolutionary perspective on sex
differences
➢ Sexual selection and parental investment
➢ Mating preferences
➢ Young men: risk, violence and honour
➢ Cuckoldry and jealousy
Natural selection and behavior
Evolutionary psychology investigates the evolutionary origin of behavior and consequences for
current psychological mechanisms
Darwin (1859): “The Origin of Species
• Theory of natural selection: Selection in nature occurs because some organisms survive
better and reproduce better in a certain environment
→ Survival of the fittest: better adaptation to environment
→ Better fitness (= transferring next-generation genes)
• Primary interest evolution of physical features
Evolution of modern Wales:
Darwin was the first one that developed a theory
➔ Theory of Natural Selection
Some organisms survive and reproduce better
➔ Survival of the fittest
The ones who are better adapted to their environment = the fittest
Fitness= genes end up in the next generations (beneFIT )
Gemaakt door Hafsa Ait Lahcen
,An example of Natural Selection and behavior: Giraffes
Offspring= descendants
Body changes until they fit in the
environment
The primary interest of modern Darwinians, is the evolution of behavior (Altruistic behavior)
Evolutionary Psychologists usually go back in time, they search for explanations
The evolutionary perspective on human nature:
• Universal characteristics: These successful characteristics provide such an ev olutionary
advantage, that they spread throughout the population and become typical for all mankind
• An example of physical evolution
o Bipedalism: a form of terrestrial locomotion where animals move using two rear limbs
o Searching for Universal psychological features/ characteristics
Altruistic behavior
Natural Selection is selfish, so how is it possible that humans help each other?
Altruistic behavior= helping others although it may be detrimental to your own fitness
Natural Selection= seemingly selfish process
How to explain this?
The universal need to belong. Being excluded from the group was the worst thing that could happen to
you. This is extremely adaptive.
Gemaakt door Hafsa Ait Lahcen
,Baumeister & Tyce:
“Social anxiety is adaptive and functional because it prevents exclusion from a group”
And yet, we see that we don’t always help people, we help to a certain extent
Inclusive fitness and kinship (Hamilton, 1964)
Inclusive fitness= your personal reproductive success + the effects you have on the reproduction of
your genetic relatives, weighted by the degree of genetic relatedness
• Identical twin: genetic relatedness = 100%
• Parents and child: 50%
• Brother/sister: 50%
• Aunt/uncle – niece/nephew: 25%
• Cousins: 12,5%
= better fitness (of next generation) by helping (genetic) relatives
This implies:
• One takes risks for genetic relatives
• The higher the genetic relatedness the higher the risk one takes
These two aspects cover the main hypothesis of the inclusive theory
Gemaakt door Hafsa Ait Lahcen
, First example:
Daly and Wilson (1988) used inclusive fitness theory to explain differences in parental care. They
argued that biological parents invest more in their children because they share genes with them, which
increases their evolutionary success. Step-parents, who are not genetically related, have less
evolutionary incentive to invest. Their data showed that children living with stepfathers were much
more likely to experience abuse than those living with biological fathers. This pattern, known as the
“Cinderella effect,” supports the idea that genetic relatedness influences parental investment and risk
of maltreatment.
Second example:
Burnstein et al. (1994) tested predictions from inclusive fitness theory by examining whether
people are more willing to help close genetic relatives in life-or-death situations. Participants were
given hypothetical emergency scenarios (e.g., rescuing someone from a fire) and asked how likely
they would be to help various individuals (siblings, cousins, friends, acquaintances). The results
showed that people were significantly more willing to help close genetic relatives, especially in
situations involving serious danger or high cost. The degree of willingness to help closely f ollowed
genetic relatedness (e.g., more help for siblings than cousins). In less serious, everyday situations,
genetic relatedness mattered less. These findings support the idea that altruistic behavior is influenced
by evolutionary pressures to protect those who share our genes.
The bigger the relatedness, the greater the tendency to help, and even more at life or death scenarios
Kinship= less related family (ex. Cousins)
Gemaakt door Hafsa Ait Lahcen
We’re going to discuss two main concepts in this chapter:
1. Altruism and Natural Selection: an evolutionary perspective on human nature
➢ Natural selection and behavior
➢ Altruistic behavior
➢ Inclusive fitness and kinship
➢ Reciprocal altruism
2. Sexual Selection and Sex differences in Behavior: an evolutionary perspective on sex
differences
➢ Sexual selection and parental investment
➢ Mating preferences
➢ Young men: risk, violence and honour
➢ Cuckoldry and jealousy
Natural selection and behavior
Evolutionary psychology investigates the evolutionary origin of behavior and consequences for
current psychological mechanisms
Darwin (1859): “The Origin of Species
• Theory of natural selection: Selection in nature occurs because some organisms survive
better and reproduce better in a certain environment
→ Survival of the fittest: better adaptation to environment
→ Better fitness (= transferring next-generation genes)
• Primary interest evolution of physical features
Evolution of modern Wales:
Darwin was the first one that developed a theory
➔ Theory of Natural Selection
Some organisms survive and reproduce better
➔ Survival of the fittest
The ones who are better adapted to their environment = the fittest
Fitness= genes end up in the next generations (beneFIT )
Gemaakt door Hafsa Ait Lahcen
,An example of Natural Selection and behavior: Giraffes
Offspring= descendants
Body changes until they fit in the
environment
The primary interest of modern Darwinians, is the evolution of behavior (Altruistic behavior)
Evolutionary Psychologists usually go back in time, they search for explanations
The evolutionary perspective on human nature:
• Universal characteristics: These successful characteristics provide such an ev olutionary
advantage, that they spread throughout the population and become typical for all mankind
• An example of physical evolution
o Bipedalism: a form of terrestrial locomotion where animals move using two rear limbs
o Searching for Universal psychological features/ characteristics
Altruistic behavior
Natural Selection is selfish, so how is it possible that humans help each other?
Altruistic behavior= helping others although it may be detrimental to your own fitness
Natural Selection= seemingly selfish process
How to explain this?
The universal need to belong. Being excluded from the group was the worst thing that could happen to
you. This is extremely adaptive.
Gemaakt door Hafsa Ait Lahcen
,Baumeister & Tyce:
“Social anxiety is adaptive and functional because it prevents exclusion from a group”
And yet, we see that we don’t always help people, we help to a certain extent
Inclusive fitness and kinship (Hamilton, 1964)
Inclusive fitness= your personal reproductive success + the effects you have on the reproduction of
your genetic relatives, weighted by the degree of genetic relatedness
• Identical twin: genetic relatedness = 100%
• Parents and child: 50%
• Brother/sister: 50%
• Aunt/uncle – niece/nephew: 25%
• Cousins: 12,5%
= better fitness (of next generation) by helping (genetic) relatives
This implies:
• One takes risks for genetic relatives
• The higher the genetic relatedness the higher the risk one takes
These two aspects cover the main hypothesis of the inclusive theory
Gemaakt door Hafsa Ait Lahcen
, First example:
Daly and Wilson (1988) used inclusive fitness theory to explain differences in parental care. They
argued that biological parents invest more in their children because they share genes with them, which
increases their evolutionary success. Step-parents, who are not genetically related, have less
evolutionary incentive to invest. Their data showed that children living with stepfathers were much
more likely to experience abuse than those living with biological fathers. This pattern, known as the
“Cinderella effect,” supports the idea that genetic relatedness influences parental investment and risk
of maltreatment.
Second example:
Burnstein et al. (1994) tested predictions from inclusive fitness theory by examining whether
people are more willing to help close genetic relatives in life-or-death situations. Participants were
given hypothetical emergency scenarios (e.g., rescuing someone from a fire) and asked how likely
they would be to help various individuals (siblings, cousins, friends, acquaintances). The results
showed that people were significantly more willing to help close genetic relatives, especially in
situations involving serious danger or high cost. The degree of willingness to help closely f ollowed
genetic relatedness (e.g., more help for siblings than cousins). In less serious, everyday situations,
genetic relatedness mattered less. These findings support the idea that altruistic behavior is influenced
by evolutionary pressures to protect those who share our genes.
The bigger the relatedness, the greater the tendency to help, and even more at life or death scenarios
Kinship= less related family (ex. Cousins)
Gemaakt door Hafsa Ait Lahcen
