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What is evolution?
it refers to the gradual change in the heritable characteristics of a species over generations.
This change occurs due to genetic mutations, which can be beneficial, neutral, or harmful.
Evolutionary psychology applies the principles of evolution to explain human behaviour, suggesting that many behaviours today served adaptive purposes for our ancestors.
What are the key principles of evolutionary theory?
Natural Selection:
traits that increase survival and reproduction are more likely to be passed on.
E.g., animals with better camouflage survive longer and reproduce more.
Genetic Variation:
Each generation has genetic differences due to mutations.
If a mutation is beneficial, it spreads in the population over time.
Adaptation:
Over time, species develop traits that help them better fit their environment.
E.g., humans evolved opposable thumbs to manipulate objects more efficiently.
Sexual Selection:
Certain traits increase the reproductive success, even if they don’t aid survival.
E.g., peacocks have large, colourful tails to attract mates, despite making them more visible to predators.
How did Darwin contribute to evolutionary psychology?
He proposed that species evolve through natural selection.
His book introduced the idea that organisms best adapted to their environment, survive and reproduce more successfully.
His other book was applied evolutionary theory to humans, suggesting that behaviours like mate selection, self-preservation, and motherly love evolved for survival.
How does evolutionary psychology explain human behaviour?
Evolution of human traits.
human behaviours have evolved through adaptation to increase survival and reproduction.
E.g.,
Self-preservation → fight or flight response.
Mate selection → choosing partners based on health and fertility.
Parental love → ensures offspring survive and thrive.
Facial expressions → universal expressions evolved as social survival mechanisms.
Evolution and mating behaviour
sexual selection is a form of natural selection where traits that increase reproductive success are favoured.
Evolutionary argument for human mating behaviour:
Men prepare youthful, fertile women.
Women prefer men with resources and protection.
What is the role of genetics in evolutionary psychology?
genes provide instructions for creating proteins that influence physical and behavioural traits.
Genes can be “turned on” or “off” due to environmental factors (epigenetics).
Epigenetics → external influences (diet, stress, experiences) can alter gene expression without changing the DNA structure.
What are the two types of gene regulation?
Internal.
External.
What is the effect on genes from internal factors?
Hormones or chemicals.
Hormones like testosterone can influence behaviour → aggression, mating.
What is the effect of external factors on genes?
Environment, stress.
Environmental stressors can activate or suppress genes.
What are the strengths of the evolutionary theory?
Explains universal behaviours → many behaviours are observed across cultures.
Supported by empirical research → studies like Buss show cross-cultural consistency in mate preferences.
Applies to various fields → helps explain phobias, aggression, parental investment, and even mental disorders.
What are the limitations of the evolutionary theory?
Difficult to test empirically → many evolutionary hypothesis rely on historical assumptions rather than direct observation.
Confirmation bias → researchers may see what they expect to see rather than unbiased results.
Cultural and environmental factors → evolutionary explanations often underestimate the role of learning, culture, and social norms.
Animal research limitations → many evolutionary studies rely on animal models, which may not generalise to humans.
Reductionist → assumes behaviour is primarily driven by genes, ignoring social and cognitive influences.
What studies support the evolutionary theory?
Wedekind.
Buss.
When was Wedekind conducted?
1995
What is the aim of this study?
Whether one’s MHC (Major Histocompatability Complex) is related to sexual attraction or would impact it.
What are the participants of this study?
Students of a university:
49 female
The women had to use a nose spray for 14 before the experiment → support the regeneration of the nasal mucous membrane.
44 male
They were given perfume-free detergent to wash clothes and bedclothes and perfume-free soap for showering.
They were asked to not use any deodorants or perfumes, to refrain from smoking tobacco or drinking alcohol, to avoid all spicy foods, and to not engage into any sexual activity.
What was the procedure of this study?
Each participant was “typed” based on their MHC.
The men were asked to wear a T-shirt for two nights and to keep the T-shirt in an open plastic bag during the day.
Two days later the women were asked to rank the smell of 7 T-shirts, each in a cardboard box with a smelling hole. The women were tested whenever possible in the second week after the beginning of menstruation, as women tend to be most odor-sensitive at this time.
3 of the 7 boxes contained t-shirts from men with MHC similar to the woman’s.
3 of the 7 boxes contained t-shirts from men with MHC dissimilar to the woman’s.
1 of the 7 boxes contained an unworn t-shirt to act as a control.
Alone in a room the women scored the odors of the t-shirts for:
1 Intensity (0-10)
2 Pleasantness and sexiness (0-10, 5=neutral)
What were the results of this study?
Women scored higher the men with odors dissimilar to their MHC.
What was the conclusion of this study?
This suggests that the MHC may influence human mate choice.
Tell me about the study of Wedekind.
Date: 1995
Aim: Whether one’s MHC (Major Histocompatability Complex) is related to sexual attraction or would impact it.
Participants:
Students of a university:
49 female
The women had to use a nose spray for 14 before the experiment → support the regeneration of the nasal mucous membrane.
44 male
They were given perfume-free detergent to wash clothes and bedclothes and perfume-free soap for showering.
They were asked to not use any deodorants or perfumes, to refrain from smoking tobacco or drinking alcohol, to avoid all spicy foods, and to not engage into any sexual activity.
Procedure:
Each participant was “typed” based on their MHC.
The men were asked to wear a T-shirt for two nights and to keep the T-shirt in an open plastic bag during the day.
Two days later the women were asked to rank the smell of 7 T-shirts, each in a cardboard box with a smelling hole. The women were tested whenever possible in the second week after the beginning of menstruation, as women tend to be most odor-sensitive at this time.
3 of the 7 boxes contained t-shirts from men with MHC similar to the woman’s.
3 of the 7 boxes contained t-shirts from men with MHC dissimilar to the woman’s.
1 of the 7 boxes contained an unworn t-shirt to act as a control.
Alone in a room the women scored the odors of the t-shirts for:
1 Intensity (0-10)
2 Pleasantness and sexiness (0-10, 5=neutral)
Results:
Women scored higher the men with odors dissimilar to their MHC.
Conclusion: this suggests that the MHC may influence human mate choice.
How do you link this study to the theory?
It provides insights into evolutionary processes by showing that individuals are attracted ti the scent of potential partners with different immune system genes, suggesting that this preference enhances genetic diversity and offspring survival, thereby playing a role in human evolution.
Evaluate the study.
This study has been successfully replicated by Jacob et al.
The theory is too reductionist → oversimplifies the behaviour of human mate selection by bringing it down to the MHC, ignoring cognitive and sociocultural factors.
Double-blind study → neither the researchers nor the participants knew which t-shirt they were being exposed to at any point of the study → minimise demand characteristics.
The results can’t be generalised → sample was limited to a specific age and culture.
When was Buss conducted?
1989.
What is the aim of this study?
To test three evolution-based assumptions about human mate selection in a large cross-cultural sample:
As men are searching for women with high reproductive value, they will favor youth and physical appearance;
As women are searching for men who will invest in their offspring, they will favour a man with the resources he can provide;
As men do not want to invest in another man’s offspring, chastity will be highly valued.
What was the sample of this study?
They used 37 samples taken from 33 countries with 10,000 participants.
Most countries had a sample of at least 100 participants.
The samples used from each country were collected using different techniques.
What was the procedure of this study?
Each sample was asked to complete 2 surveys.
1st survey:
Collected biographical data,
They were asked:
What age they preferred to marry,
The preferred age difference between self and spouse, and
How many children they want.
To rate 18 characteristics on how important they are using a four-point scale (0=irrelevant, 3=indispensable)
2nd survey:
it provided 13 characteristics that participants were asked to rank in terms of desirability in mate.
What were the results of this study?
They supported two of the three assumptions:
36/37 samples → women valued “good financial prospects” in potential mate, more than males did.
In all samples → men preferred younger mates.
Females preferred mates that are older than they are.
34/37 samples → males valued physical attractiveness in potential mates more than females do → not statistically significant.
23/37 samples → valued chastity.
What was the conclusion of this study?
Two of the three assumptions are true.
The only one that was not supported was that chastity is valued by men to guarantee the paternity of the offspring, but it could be more of a cultural construct than a biological one.
Tell me about the study of Buss.
Dat: 1989
Aim:
To test three evolution-based assumptions about human mate selection in a large cross-cultural sample:
As men are searching for women with high reproductive value, they will favor youth and physical appearance;
As women are searching for men who will invest in their offspring, they will favour a man with the resources he can provide;
As men do not want to invest in another man’s offspring, chastity will be highly valued.
Participants:
They used 37 samples taken from 33 countries with 10,000 participants.
Most countries had a sample of at least 100 participants.
The samples used from each country were collected using different techniques.
Procedure:
Each sample was asked to complete 2 surveys.
1st survey:
Collected biographical data,
They were asked:
What age they preferred to marry,
The preferred age difference between self and spouse, and
How many children they want.
To rate 18 characteristics on how important they are using a four-point scale (0=irrelevant, 3=indispensable)
2nd survey:
it provided 13 characteristics that participants were asked to rank in terms of desirability in mate.
Results:
They supported two of the three assumptions:
36/37 samples → women valued “good financial prospects” in potential mate, more than males did.
In all samples → men preferred younger mates.
Females preferred mates that are older than they are.
34/37 samples → males valued physical attractiveness in potential mates more than females do → not statistically significant.
23/37 samples → valued chastity.
Conclusion:
Two of the three assumptions are true.
The only one that was not supported was that chastity is valued by men to guarantee the paternity of the offspring, but it could be more of a cultural construct than a biological one.
How do you link this study to the theory?
It explores evolutionary psychology by examining mate preferences across cultures, revealing consistent patterns such as preference for traits indicating health and fertility, which supports the theory that these preferences evolved to enhance reproductive success.
Evaluate the study.
The sample → cannot represent the whole country, as it covers only a part of the population, and excludes rural, less-educated, and lower levels of socioeconomic status.
Although, the highly diverse sample allows the findings to be generalised as a whole and to support the theory more, as the findings were consistent in most cases.
The used surveys → quantitative data + a 4-point scale which helped the participants to not choose the mean, but we don’t know how each one interpreted that scale of ranking.
Parallel forms reliability → same responses were given o two different forms of a survey or test.
The results do not tell us why these preferences exist → we don’t know if the preferences are a result of genetic differences or socialisation.
