Evolutionary Psychology
Paper: Evolutionary Theory and the Ultimate–Proximate Distinction in the Human Behavioural
Sciences
- Ultimate explanations (evolutionary function, “why?”) vs proximate explanations (way in
which functionality is achieved, “how?”)
-
- Darwin: those heritable traits that are associated with greater reproductive success will,
over time, tend to accumulate in a population, and that those associated with reduced
reproductive success will disappear
o Natural selection: process favouring traits that increase reproductive success and its
consequences (organisms appear to be designed to maximise fitness)
- Fisher: fundamental theorem of natural selection → natural selection produces organisms
that appear to be designed to maximise their fitness
o Fitness = number of offspring an individual produces that survive to reproductive
age
o For social behaviours: inclusion of gene being able to influence transmission to next
generation indirectly by influencing reproductive success of other individuals
carrying that gene
o Hamilton: gene’s increase in frequency is due not only to the direct fitness effects
that it has on the focal individual, but also to the indirect fitness effects that it has
on the fitness of the focal individual’s relatives
▪ Hamilton’s rule: behaviour or trait will be favoured by selection when rb > c,
where c is the fitness cost to the actor, b is the fitness benefit to the
recipient, and r is their genetic relatedness
- Inclusive fitness = sum of direct and indirect fitness; maximand of natural selection
- Kin selection = selection of the indirect component of inclusive fitness
- The evolution of cooperation: proximate phenomena used to address ultimate questions
o Reason for commonality of misunderstandings
▪ Proximate explanations often desideratum for research
▪ Some terms have different meanings, one at ultimate level (net effects on
direct and indirect fitness) and one at proximal level (mental states)
, •
• Associated problem: use of proxy measures for fitness in
experimental research
▪ The use of intentional language in evolutionary explanation
• Intentional language used in evolutionary psychology =
anthropomorphic shorthand for ultimate explanations
- Culture and the ultimate-proximate distinction: cultural transmission as a proximate
mechanism
o Transmitted culture = those behaviours or traditions that individuals acquire through
teaching, imitation, and other forms of social transmission
o Cultural transmission as proximate mechanism --> describes one of causal triggers of
the expression of some behaviour
▪ Argument that cultural transmission changed selection pressures irrelevant -
-> proximate mechanisms often change selection pressures
▪ Example of linguistic structure: observed structure of language as
consequence of process of cultural transmission
• Establishes the presence of cultural transmission as a possible causal
trigger of the emergence of linguistic structure
• Language structure being based on transmitted culture =/=
challenge to natural selection as ultimate explanation of why
linguistic structure exists at all --> rather challenge to accounts
based on highly structure Universal Grammar as proximate
explanation of how functionality is achieved
- Epigenetic inheritance as a proximate mechanism
o Epigenetics = processes that are “above” or otherwise separate to genetic change
▪ Best understood as proximate mechanism
o Example: low-frequency grooming rats producing low-frequency grooming offspring
--> consequence of behavioural inheritance
, ▪ Increase in frequency of low grooming under stressful conditions, high
grooming in benign conditions --> proximate mechanisms calibrate
phenotype according to environment
o Epigenetic mutations = switches evolved by natural selection to enable genes to
exhibit conditional behaviour
o Recognition of mechanistic character of epigenetics = key to clarifying future
research --> only possible if seen as proximate mechanism
Questions – Assignment Lecture 1
1) What is meant by the “Environment of Evolutionary Adaptedness”?
- Group of selection pressures occurring during an adaptation’s period of evolution
responsible for producing the adaptation (Toby and Cosmides 1992)
- ancestral environment to which a species is adapted
- → any factor that impacts reproductive success
- Each adaptation has its own EEA, or set of adaptive problems, that shaped it over
evolutionary time
- African savanna → where most of ancestor’s adaptations took place
2) What is the “Westermarck Effect” and how does it support the existence of an adaptive
mechanism for incest avoidance?
- Reverse sexual imprinting
- i.e., psychological hypothesis that people tend not to be attracted to peers with whom they
lived like siblings before age six
- existence of Westermarck effect supports existence of incest avoidance because it is
adaptive → more gene variability
- → heuristic
3) Proximate and Ultimate Explanations offered for why women talk more than men?
- Proximate:
o Hormones (dopamine and oxytocin released by female brain when talking)
o Brain differences (empathy/communication vs understanding systems)
- Ultimate:
o Historical explanations (gathering/watching children vs hunting requires different
skills) → better fit with tasks/environment explaining why it is differentially adaptive
for men and women
- Problem with line of reasoning
o Too simplistic, only captures one specific situation
o We do not actually know what men and women were doing → claim not falsifiable
▪ Just-so stories
4) In this graph, you find the results from a study testing an ultimate explanation for the 'Post-
coital Time Interval' (PCTI), which is the time it takes to fall asleep after sex. The hypothesis
under investigation was that the PCTI functions to facilitate bonding or – if shortened – to
avoid bonding; Reducing the time before sleep onset following sexual intercourse
supposedly would curtail commitment conversations and interfere with opportunities for
, promoting emotional connectedness. The prediction was that as men are evolutionary less
inclined towards bonding than women, their PCTI's would be shorter. Do these result
support the hypothesis? Please explain.
- It does not support the hypothesis
o No differences after sex
o Only difference when not having sex → irrelevant to hypothesis
Lecture 1
- Why do people help others?
o Help in return (ultimate)
o To feel better about ourselves (proximate) → intrapsychic phenomenon
o Prestige / status (ultimate) → external effect
o Feels nice (proximate)
o Group benefits (ultimate)
o To follow norms (proximate) → learned process, through cultural inheritance
o Empathy (proximate)
o Responsibility (role) (proximate)
- Gene-centric view of life: we are carriers of genes
- Brain has to have adaptive function → is very costly, would have been selected against
otherwise
o Has special mechanisms
- Adaptive problem = set of recognisable cues that identify either an opportunity to increase
fitness or avoid fitness loss
- Cultural evolution much faster than genetic evolution →stone age minds in modern skulls
o Gene co-evolutionary mismatch
- Three products of evolutionary processes
o Adaptations
o By-products
o Random effect / noise
Paper: Childhood Experience, Interpersonal Development, and Reproductive Strategy – An
Evolutionary Theory of Socialisation
Paper: Evolutionary Theory and the Ultimate–Proximate Distinction in the Human Behavioural
Sciences
- Ultimate explanations (evolutionary function, “why?”) vs proximate explanations (way in
which functionality is achieved, “how?”)
-
- Darwin: those heritable traits that are associated with greater reproductive success will,
over time, tend to accumulate in a population, and that those associated with reduced
reproductive success will disappear
o Natural selection: process favouring traits that increase reproductive success and its
consequences (organisms appear to be designed to maximise fitness)
- Fisher: fundamental theorem of natural selection → natural selection produces organisms
that appear to be designed to maximise their fitness
o Fitness = number of offspring an individual produces that survive to reproductive
age
o For social behaviours: inclusion of gene being able to influence transmission to next
generation indirectly by influencing reproductive success of other individuals
carrying that gene
o Hamilton: gene’s increase in frequency is due not only to the direct fitness effects
that it has on the focal individual, but also to the indirect fitness effects that it has
on the fitness of the focal individual’s relatives
▪ Hamilton’s rule: behaviour or trait will be favoured by selection when rb > c,
where c is the fitness cost to the actor, b is the fitness benefit to the
recipient, and r is their genetic relatedness
- Inclusive fitness = sum of direct and indirect fitness; maximand of natural selection
- Kin selection = selection of the indirect component of inclusive fitness
- The evolution of cooperation: proximate phenomena used to address ultimate questions
o Reason for commonality of misunderstandings
▪ Proximate explanations often desideratum for research
▪ Some terms have different meanings, one at ultimate level (net effects on
direct and indirect fitness) and one at proximal level (mental states)
, •
• Associated problem: use of proxy measures for fitness in
experimental research
▪ The use of intentional language in evolutionary explanation
• Intentional language used in evolutionary psychology =
anthropomorphic shorthand for ultimate explanations
- Culture and the ultimate-proximate distinction: cultural transmission as a proximate
mechanism
o Transmitted culture = those behaviours or traditions that individuals acquire through
teaching, imitation, and other forms of social transmission
o Cultural transmission as proximate mechanism --> describes one of causal triggers of
the expression of some behaviour
▪ Argument that cultural transmission changed selection pressures irrelevant -
-> proximate mechanisms often change selection pressures
▪ Example of linguistic structure: observed structure of language as
consequence of process of cultural transmission
• Establishes the presence of cultural transmission as a possible causal
trigger of the emergence of linguistic structure
• Language structure being based on transmitted culture =/=
challenge to natural selection as ultimate explanation of why
linguistic structure exists at all --> rather challenge to accounts
based on highly structure Universal Grammar as proximate
explanation of how functionality is achieved
- Epigenetic inheritance as a proximate mechanism
o Epigenetics = processes that are “above” or otherwise separate to genetic change
▪ Best understood as proximate mechanism
o Example: low-frequency grooming rats producing low-frequency grooming offspring
--> consequence of behavioural inheritance
, ▪ Increase in frequency of low grooming under stressful conditions, high
grooming in benign conditions --> proximate mechanisms calibrate
phenotype according to environment
o Epigenetic mutations = switches evolved by natural selection to enable genes to
exhibit conditional behaviour
o Recognition of mechanistic character of epigenetics = key to clarifying future
research --> only possible if seen as proximate mechanism
Questions – Assignment Lecture 1
1) What is meant by the “Environment of Evolutionary Adaptedness”?
- Group of selection pressures occurring during an adaptation’s period of evolution
responsible for producing the adaptation (Toby and Cosmides 1992)
- ancestral environment to which a species is adapted
- → any factor that impacts reproductive success
- Each adaptation has its own EEA, or set of adaptive problems, that shaped it over
evolutionary time
- African savanna → where most of ancestor’s adaptations took place
2) What is the “Westermarck Effect” and how does it support the existence of an adaptive
mechanism for incest avoidance?
- Reverse sexual imprinting
- i.e., psychological hypothesis that people tend not to be attracted to peers with whom they
lived like siblings before age six
- existence of Westermarck effect supports existence of incest avoidance because it is
adaptive → more gene variability
- → heuristic
3) Proximate and Ultimate Explanations offered for why women talk more than men?
- Proximate:
o Hormones (dopamine and oxytocin released by female brain when talking)
o Brain differences (empathy/communication vs understanding systems)
- Ultimate:
o Historical explanations (gathering/watching children vs hunting requires different
skills) → better fit with tasks/environment explaining why it is differentially adaptive
for men and women
- Problem with line of reasoning
o Too simplistic, only captures one specific situation
o We do not actually know what men and women were doing → claim not falsifiable
▪ Just-so stories
4) In this graph, you find the results from a study testing an ultimate explanation for the 'Post-
coital Time Interval' (PCTI), which is the time it takes to fall asleep after sex. The hypothesis
under investigation was that the PCTI functions to facilitate bonding or – if shortened – to
avoid bonding; Reducing the time before sleep onset following sexual intercourse
supposedly would curtail commitment conversations and interfere with opportunities for
, promoting emotional connectedness. The prediction was that as men are evolutionary less
inclined towards bonding than women, their PCTI's would be shorter. Do these result
support the hypothesis? Please explain.
- It does not support the hypothesis
o No differences after sex
o Only difference when not having sex → irrelevant to hypothesis
Lecture 1
- Why do people help others?
o Help in return (ultimate)
o To feel better about ourselves (proximate) → intrapsychic phenomenon
o Prestige / status (ultimate) → external effect
o Feels nice (proximate)
o Group benefits (ultimate)
o To follow norms (proximate) → learned process, through cultural inheritance
o Empathy (proximate)
o Responsibility (role) (proximate)
- Gene-centric view of life: we are carriers of genes
- Brain has to have adaptive function → is very costly, would have been selected against
otherwise
o Has special mechanisms
- Adaptive problem = set of recognisable cues that identify either an opportunity to increase
fitness or avoid fitness loss
- Cultural evolution much faster than genetic evolution →stone age minds in modern skulls
o Gene co-evolutionary mismatch
- Three products of evolutionary processes
o Adaptations
o By-products
o Random effect / noise
Paper: Childhood Experience, Interpersonal Development, and Reproductive Strategy – An
Evolutionary Theory of Socialisation
