lecture 9 - evolution of a social brain

Question 1

what are the chief threats to humans?

Answer 1

1 - disease
2 - other humans

Question 2

Why do babies have such big brains?

Answer 2

Helpless at the start .. But capable of learning so much?
… and organised in a particular way?

Question 3

Why do we do crazy things?

Answer 3

(and other things that do not seem related to survival or having more offspring) - the clues in the context
Simple answer:
‘we live in groups with complex social networks’ (obviously the complete answer is more complex)

Question 4

Families, tribes, teams, society…

Answer 4

Natural selection = “survival of the fittest”
What kind of fitness? Fit to the environment (i.e. traits that are advantageous in a given environment will prosper, on average)
What is the most influential feature of most human environments?
OTHER HUMANS!

Question 5

ancestor species - what were they like?

Answer 5

australopithecus afarensis

several species, all in Africa, some lived at same place at same time

some more ‘robust’
some more ‘gracile’
we evolved from a more gracile group

larger brains than Au. afarensis. flaked stone tools
these were successful ape species - surviving for perhaps 1 million years or more

lineages not yet agreed, but out lineage evolve from gracile type

Question 6

fossil records

Answer 6

are patchy as more are discovered all the time.

Question 7

out of Africa, series 1 … Homo Erectus

Answer 7

1st example of ape species of human lineage that came out of Africa into Asia

used fire, tools, clothes (and maybe boats) Built shelters, even houses. may have had language. lasted over 1 million years.

may have invented boats

a very successful species

the way we run makes us different from other apes

Question 8

out of Africa, series 2

Answer 8

archaic Homo sapiens in africa

called neanderthals in Europe - they share same language gene as us so likely has some language ability

Denisovans in asia and russia

don’t think any of these species got to n and s America or autsralia

Question 9

out of Africa, series 3

Answer 9

sapiens got into australia and north and South America

never simple interbreeding - Intriguing evidence from DNA (Neanderthal, Denisovan and modern human)

Y chromosome

Skin and immune effects

we have neanderthal DNA in our DNA so there was interbreeding

Question 10

why did sapiens outcompete the others?

Answer 10

Accumulated knowledge and technologies?
Language?
Lived longer and less disease?
group size?

neanderthals lived in family groups rather than large tribes so would maybe move - into Western Europe

Neanderthals could have suffered disease or didn’t live as long as sapiens

Question 11

families, tribes, teams, society

Answer 11

Altruism and ‘kin selection’
Natural selection actually works at the level of genes, not individual animals

“Altruistic behaviors will be favored by selection if costs are less than the benefits discounted by coefficient of relatedness between actor and recipient” (Hamilton, 1964)

Hamiltons rule: r B > C
r = coefficient of relatedness (proportion of genes shared)

r- Descendant Kin- Non-desc. Kin
0.5 - Offspring - Siblings
0.25 - Grandchildren
- Half-sibling, Nephews, Nieces
0.125- G-Grandchildren- Cousins

‘Inclusive fitness’ = the number of offspring equivalents that an individual rears, rescues or otherwise supports through its behaviour (regardless of who begets them)

Question 12

families, tribes, teams, society - altruism and ‘kin selection’

Answer 12

Altruism and ‘kin selection’
Natural selection actually works at the level of genes, not individual animals

A kin altruism gene does not program individuals to take intelligent action on its behalf; it specifies a simple behavioral rule of thumb such as “feed squawking gapes in the nest in which you live.” It is this unconscious rule that will become universal when the gene becomes universal. (Dawkins 1979)

If families [genetic relatives] happen to go around in groups, this fact provides a useful rule of thumb for kin selection: ‘care for any individual you often see’.” (Dawkins 1979)

For this reason, kin selection does not require that animals can recognise their kin.

Question 13

families, tribes, teams, society - reciprocal altruism

Answer 13

Remember, the environment is made up of other humans…

Reciprocal Altruism
Conditions:
Opportunity for frequent interactions
Ability to keep track of support given and received (memory and gossip)
Preferentially provide support to individuals who support
these effects can be shown in computational models of evolution
… in turn this trait then becomes something advantageous to look for in a partner as it would help your children to inherit (and/or learn) the trait.

This has almost certainly been true for at least 10 million years; all African apes live in groups with complex social interactions, where relationships with other members of the group are key to success.

Question 14

Families, tribes, teams, society…
- cooperation and group selection

Answer 14

helping your group also has some benefit to you

Many behaviours that help group cohesion, survival and expansion can be indirectly beneficial to your own family’s success, and the survival of genetics you share with members of your tribe.

Therefore if genes exist that favour those behaviours, they can become more common in the next generations

And vice versa – if mutations occurred that tended to cause behaviours that harmed group cohesion, made groups smaller, or threatened your inclusion in a group, these could be strongly selected against

In the extreme - if most of your tribe is wiped out, or if you get separated from it, survival chances were likely low for you and your kin.

your group is your protection if its smaller at more risk. creatures who keep the group and it benefits them as it maintains a large group which is critical to your survival

Question 15

This means two things:

Answer 15

Natural selection can sometimes operate at the level of groups / colonies / tribes (‘group selection’ or ‘multilevel selection’).
Genes that support an instinct to help your tribe can proliferate (both because tribe members are often related to you, and also the tribe is your protection and support).
note that this is not the same as simply saying animals will act for the benefit of their species or groups; such behaviour would be selected against if it means individuals without the allele supporting this behaviour benefit more than the individuals showing the behaviour

Question 16

KEY CONCEPT:
Is the question of biology/instinct vs culture really ‘either/or’?

Answer 16

Remember, the environment is made up of other humans…
Gene-Culture coevolution - not either or
Cultural features (i.e. social learning, responses to disease) that benefitted survival and expansion of tribes became more widespread.
In turn, they influenced genetic selection; because the environment has changed. E.g. cooking led to gut reduction; Projectile weapons led to changes in human hands and shoulders (humans are much better at throwing objects than chimpanzees); Language led to larynx and brain changes; - freed up time - feeding Brains is important to maintain them
Chimpanzee groups also have cultural differences (e.g. in the types of tools they use and teach their offspring to use).
At the same time, selection pressures on human brains have worked not just on specific abilities, but on the general ability and instinct to be social and learn from others – to ‘belong’ to your tribe.
Summary:
Natural selection simply means that those individuals most successful at having successful offspring have a stronger genetic influence on the next generations than those who have fewer or less successful offspring….

Question 17

How we behave in groups/tribes (see social lectures) is one of the major things that determines:

Answer 17

• who has sex with whom (social expectations and opportunities, marriage customs etc)
• what helps offspring survive and thrive (cooperation, status, response to disease, etc etc).
  Being social animals and having cultures is arguably the most critical factor of our evolutionary heritage… during human evolution the environment has been made up of other humans
  To a first approximation:
• most behaviour is learnt;
  natural selection gave us the machinery to learn it efficiently, the drive to do things that help learning, and the drive to learn the types of things that are helpful to survival in groups, including a drive to do what others do (the route to culture?)

Question 18

Natural selection - more concepts
Don’t fall into ‘the Naturalistic Fallacy’

Answer 18

It is a fallacy to assume that what is natural
is also good or inevitable
It is therefore illogical to justify (rather than seek to understand) certain behaviours or inequalities based on evolutionary theories
We have to face up to the fact that aggression, war, murder, theft, deceit, unfaithfulness, racism, sexism, other discrimination and a host of other unpleasant behaviours have likely been part of the ‘natural’ behaviour and evolutionary environment of our tribal ancestry.
That does not justify them or make them inevitable – moreover, understanding the heritage might help us minimise them
e.g. Chief threats:
1. Disease
2. Other humans
This has probably always been the case..
But that doesn’t mean we have to accept it always will be.

Question 19

Don’t devalue or dismiss behaviours just because they have a (known or plausible) evolutionary explanation

Answer 19

Our ‘natural behaviours’ also include friendship, altruism, creativity, teamwork, music, gossip, fun, adventure, love, sex and sharing tasty food…
Which brings us to… levels of explanation…
Proximal and ultimate explanations
e.g. Why do we like music?
e.g. Why do nearly all cultures have dancing?
Why do we like music and dancing?
Love of music/dance has been naturally selected?
(vs?)
“We dance because its fun!
Are these explanations mutually exclusive?
Why is dancing fun?
(why are eating and sex enjoyable?)

I danced because it’s fun. I ate because I was hungry ——> “Proximal” explanations - social explanation

dancing influences mate choice. eating influences survival —–> “ultimate” explanations - evolutionary explanation

Question 20

Natural selection: more concepts
Proximal and ultimate explanations

Answer 20

Why do we like music and dancing?

Love of music/dance has been naturally selected?
vs
“We dance because its fun!”
vs
“We dance because its culturally/socially learnt”
Are these explanations mutually exclusive

I danced because I was copying my peers (social learning)
—–> “Proximal” explanation - social explanation

Social learning increases inclusive fitness
—-> “Ultimate” explanation - evolution explanation

Question 21

Natural selection - counterintuitive cases

Answer 21

PUZZLE: Many human behaviours or traits may not have an immediately obvious benefit, appear detrimental, or even demonstrably reduce survival and/or offspring (either directly or by diverting time and resources)
e.g. altruism, adventure/risk-seeking, colour blindness, music, mental illness (e.g. schizophrenia, depression, anxiety),
And many of these traits have known genetic heritability (especially mental health)…

Question 22

“Why has heritable risk for mental health challenges not been eliminated by natural selection?”
What types of explanation are possible?

Answer 22

Possibility 1: too recent. i.e. the genetic risk didn’t lead to detrimental effects in previous environments. or deficit is learnt. - seems unlikely for most mental health challenges
Possibility 2: the risk may be an unavoidable side effect of something positive (the genes normally benefit something, but carry the risk of coming together with other genes to raise the probability of something detrimental (we met this with the black death and auto-immune diseases). - genetic predisposition for mental health challenges were previously an adv - side effects of creativity - each human is different
Possibility 3: Being a Carrier may have no (or positive) effect on offspring numbers or survival (e.g. colour blindness). - for majority of people genetic predisposition does no harm
Possibility 4: having a spectrum may be beneficial to most individuals and/or to group success

Question 23

Brain functions from an evolutionary perspective:
Case study: anxiety

Answer 23

Anxiety: an evolutionary approach.
Melissa Bateson, Ben Brilot, Daniel Nettle,Canadian Journal of Psychiatry, 2011
…We argue that the function of the human anxiety response, and homologues in other species, is to prepare the individual to detect and deal with threats….
Try to understand the gist, not every detail…
The paper revises some general concepts we have met
Variance in populations (see natural selection slides in previous lecture)

Comparative and optimisation approaches (see also colour vision case study)

The naturalistic fallacy

Ultimate (evolutionary) explanations vs proximate (mechanistic) explanations

Question 24

Sociobiology and evolutionary psychology

Answer 24

• Sociobiology has been defined as ‘the systematic study of the biological basis of all social behaviour’ (Wilson, 1975).
• It represents the synthesis of research findings regarding social behaviour from many other fields of science, including those from evolutionary psychology, anthropology and behaviour genetics.
• Evolutionary psychology and behaviour genetics are more specific fields than sociobiology in the sense that both are concerned with phenomena such as intelligence and cognition, in addition to social behaviour.
• Sociobiologists are especially interested in understanding the evolutionary roots of our modern-day social actions. Often, sociobiologists study the evolutionary bases of social behaviour in non-human animals and then extrapolate from those species to humans (Barash, 1982).
  Sociobiology represents an interface between the biological sciences and psychology. However, not all psychologists are convinced of the sociobiologists’ claims, arguing that sociobiology is too simplistic and that its emphasis on genetics inadequately explains the complexities of human behaviour.

Question 25

Reproductive strategies and biological basis of parenting

Answer 25

• Perhaps the most important social behaviours related to survival are those related to mating and parenting.
• According to Puts (2010), around 75 per cent of the papers published in the journals Evolution, Hormones and Behaviour and Human Nature between 1997 and 2007 were on mate choice.
• A focal point of sociobiological research and theory has been understanding more about the different kinds of social organisation that result from reproductive strategies – systems of mating and rearing offspring.
• We assume that most Western sexual relationships are monogamous: the mating of one female and one male. If mating is successful, the individuals share in the raising of the child or children. But monogamy is just one of several reproductive strategies sexual creatures employ in mating and the rearing of offspring (Barash, 1982).
• Three other major classes of reproductive strategy are also possible:

*Polygyny: one male mates with more than one female.
*Polyandry: one female mates with more than one male.
*Polygynandry: several females mate with several males.

• According to Trivers (1972), these four reproductive strategies evolved because of important sex differences in the resources that parents invest in conceiving and rearing their offspring.
  Parental investment is the time, physical effort and risks to life involved in procreation and in the feeding, nurturing and protecting of offspring. According to sociobiologists, parental investment is a critical factor in mate selection. An individual who is willing and able to make a greater investment is generally more sought after as a mate and is often more selective or discriminating when selecting a mate (Trivers, 1972).

Question 26

selecting a mate

Answer 26

• Given that a human female will gestate for nine months, she should be highly selective about choosing a mate. On the basis of Trivers’s theory, it is possible to predict that women will express an evolved preference for men who have high status and will divorce those who do not contribute the expected resources or who divert them to other women and children (Buss, 1995).
• In some species, which reproduce through sex, competition for mates leads to sexual selection – selection for traits specific to sex, such as body size or ornamentation or particular patterns of behaviour.
• For example, in some animals, such as buffalo, females select mates based on the male’s ability to survive the skirmishes of the rutting (mating) season.
• In general, the larger and more aggressive males win these battles and gain access to more females and enjoy greater reproductive success.This competition is assisted by the physical differences between men and women. For example, if fat is factored out, men are 40 per cent heavier and have 60 per cent more muscle than women, have 80 per cent greater arm muscle, 50 per cent lower body mass muscle (Lassek and Gaulin, 2008, 2009), and 90 per cent more upper body strength. Their sprint times are 22 per cent faster, and they can leap 45 per cent higher; the average man is stronger than 99 per cent of women (Lassek and Gaulin, 2009).
• Men are also more likely to be aggressive, as are boys; they attack more, hit more and restrain more. These factors, together with masculine features such as beards and deep voices, are important factors in mate choice and contribute to contest competition – a way in which men can eliminate (metaphorically) other men who compete for female attention.
• It is women who normally express choice for mates and so men vie for female attention using whatever means they believe will be successful and this means removing opposition. Therefore, men compete for sexual attention and women select based on so-called gene quality (which is what fitness, strength, masculinity are thought to convey).
  Men prefer women with faces that are gracile – not lined, hirsute or masculine, and who have minimal body hair and high voices (Rilling et al, 2009). These features all signify youthfulness and, therefore, reproductivity. They also prefer a particular waist-to-hip ratio, as you will see later. It is interesting to note that no other primate has the fat distribution of women – on the breasts and hips (Pond and Mattacks, 1987).

Question 27

men social dominance

Answer 27

• Evolution, however, has led to the development of a male brain that can go beyond mere punch-ups and Tom Jones impersonations: men also use humour, music, poetry and other creative vehicles to attract a mate and these factors are considered important to women in a long-term relationship (Gangestad et al, 2007; Prokosch et al, 2009).
• Laughter is used as a signal of social dominance; if low and high-status individuals are left to talk among themselves and their laughter is measured, dominant and submissive laughter is found, depending on the status of the individual (Oveis et al, 2016). High-status people were dominant and disinhibited laughers whereas low-status laughers were inhibited. Low-status individuals were more likely to shift their type of laughter across contexts.
• Men also tend to prefer to hear jokes by other men when other men’s voice pitch is lower (Cowan et al, 2015) and prefer low-pitched men as friends if they report high levels of self-reported dominance.
• Polygyny is by far the most common reproductive strategy among humans. Eighty-four per cent of human societies practise polygyny or allow men who are either wealthy or powerful to practise it (Badcock, 1991).
• Monogamy is the next most popular reproductive strategy, with about 15 per cent of all human cultures practising it.
  Polyandry and polygynandry are both rare: combined, these two reproductive strategies dominate in fewer than 1 per cent of all human cultures.

Question 28

Polygyny - high female and low male parental investment

Answer 28

• In many species, the female makes the greater parental investment. According to evolutionary biological theory, whether one is an ova producer or a sperm producer defines the nature of one’s parental investment.
• Among most mammals (including humans), the costs associated with reproduction are higher for females than for males. First, females have fewer opportunities than males to reproduce.
• Generally, females produce only one ovum or a few ova periodically, whereas males produce vast quantities of sperm over substantially shorter time intervals.
• Secondly, females carry the fertilised ovum in their bodies during a long gestation period, continuously diverting a major portion of their own metabolic resources to nourish the rapidly growing foetus.
• Females also assume all the risks that accompany pregnancy and childbirth, including physical discomfort and possible death.
• The male’s contributions to reproduction are, at a minimum, the sperm and the time needed for intercourse.
• Thirdly, after the offspring is born, females may continue to devote some of their metabolic resources to the infant by nursing it.
• Just as important, they usually devote more time and physical energy than males to caring for the newborn.
  In addition, a female can only bear a certain number of offspring in a lifetime, regardless of the number of males with whom she mates.

Question 29

In contrast, a male is limited in his reproductive success only by the number of females he can impregnate

Answer 29

For example, consider the differences between females and males in our species. If a woman became pregnant once a year for ten years, she might possibly conceive ten children – only a fraction of the number of children that a man is capable of fathering over the same interval. If a man impregnated a different woman every month for ten years, he could have fathered 120 children.
* This example is hardly an exaggeration. According to the Guinness Book of World Records, the largest number of live births to one woman is 69 (she had several multiple births). In contrast, King Ismail of Morocco is reported to have fathered 1,056 children.
* In many polygynous species, intense competition for the opportunity to mate occurs among males.
* The competition almost always involves some sort of physical confrontation or display: that is, males fight among themselves for the opportunity to display or mate. Usually, the larger, stronger and more aggressive male wins, which means that only he will mate with the available females in the vicinity. If one of the smaller, weaker males attempts to mate with a female, he is generally chased away by the victorious male.
Because females in polygynous species invest so heavily in their offspring, they are – according to sociobiologists – usually highly selective of their mates, choosing to mate only with those males who possess specific attributes, such as physical size, strength and aggressiveness. Such selectivity makes adaptive sense for both the female and her progeny.

Question 30

Polyandry - high male and low female parental investment

Answer 30

• Polyandry is a rare reproductive strategy among humans and non-existent in other mammals. It is more prevalent among species that lay eggs. Once the eggs are laid, then either the male or the female may take care of them, although in many instances the male makes the greater investment of time and effort.
• An example of polyandry in humans is found among some of the people who live in remote Himalayan villages. These people are extremely poor and live in a harsh environment, which makes their primary livelihood, farming, difficult. In order to prevent the dissolution of family farms through marriage, families that have more than one son limit the number of marriages to only one per generation; several brothers may share the same wife.
  A female tends to marry more than one man (most often brothers) to guarantee that she will be adequately supported. In other words, the male’s primary investment – the farm, which is the source of food and some income for the family – is guarded jealously through polyandry.

Question 31

Polygynandry - group parental investment

Answer 31

• Many primates, such as chimpanzees, live in colonies in which few or no barriers are placed on which female mates with which male. In other words, the colonies are promiscuous; during periods of mating, intercourse is frequent and indiscriminate.
• What is the advantage of such a reproductive strategy?
• The primary advantage seems to be the cooperation of males and females in the colony with respect to rearing offspring. Because the males in the colony are not sure which offspring belong to them, it is in their best interest to help rear and protect all the offspring and defend their mothers.
• The unity in the colony and the lack of aggression among the males contribute directly to the general welfare of all colony members. Females and males have access to many mates, and the offspring are well cared for.
• However, a form of monogamy called a consortship is sometimes observed in polygynandrous species. For instance, one male chimpanzee may ward off other male suitors from a particular female, resulting in an exclusive sexual union. If successful, he is guaranteed the certainty of which offspring are his, albeit at some cost. There is a chance that he could be seriously injured in protecting his mate from other males, and therefore he becomes less useful as a parental investor in his offspring or those of the colony.

Question 32

Physical attractiveness 1

Answer 32

• There is evidence that some aspects of our physical appearance are preferred more than others. Some studies find that body mass index (BMI) is important, especially when full-frontal images are judged; others suggest that shape is more important if a figure is seen in profile.
• Tovee and Cornelissen (2001) found that BMI, not waist-to-hip ratio (WHR), was the best predictor of attractiveness for figures seen from the front or in profile. Both men and women gave similar ratings, thus supporting the second hypothesis, and both sexes preferred the figures with the lowest WHR (a curvaceous figure). This suggests that BMI and WHR may reflect different aspects of female health and fitness. BMI may reflect general fitness and fertility whereas WHR is a ‘more specific cue to fertility and pubertal status’ although the authors acknowledge that this cue has its limitations.
• The WHR of anorexic and healthy women is similar, for example, although the anorexic group (which is amenorrheic, i.e. not menstruating) is not fertile whereas the healthy group is.
• There is an analogous preference for low waist-to-chest ratio (WCR) in men (Maisey et al, 1999). Unlike men, who prefer a certain body size, women prefer a certain shape. This is the ‘inverted triangle’ (narrow waist, broad shoulders). The researchers suggest that if the desirable WHR in women signifies health and reproductive potential, then a desirable WCR in men signifies physical strength.
• Men’s weight, however, can influence people’s judgement of their personality. Wade et al (2007) found that thinner men were rated as more socially desirable than overweight men. Thin men and men of normal weight also received higher ratings for friendliness, trustworthiness, intelligence and mate potential.
  Bodies are often covered, and we may not be able to perceive their exact shape. Faces, however, are almost always exposed and offer an immediate source of information about physical attractiveness.

Question 33

physical attractiveness 2

Answer 33

• People with attractive faces are rated as healthier, sexier, more attractive and more fertile regardless of WHR (Furnham et al, 2001). The evidence is contrary to what we would expect from the ‘first pass filter’ theory of mate selection. This refers to the notion that WHR is the first feature we focus on to determine our attraction to a partner; if it is acceptable, we then focus on other features and behaviours to further refine our choice.
• People also find facial symmetry (where the left and right sides are almost totally symmetrical) attractive and healthy. Men with more symmetrical bodies have been reported to display more direct, sexual, competitive tactics when trying to win their date (Simpson et al, 1999) and symmetrical movers are judged to be significantly better dancers than are asymmetrical ones (Brown et al, 2005).
  Of course, physical beauty is stereotypically (and self-evidently) skin-deep. A study by Swami et al (2007) asked participants to rate line drawings of women which varied in body weight, WHR and personality (extravert, introvert). Extraverted ‘women’ were judged to be more attractive and sociable than introverted ones, indicating that non-physical features are also an important determinant of attractiveness. Women rated several characteristics as being more important in a partner than did men (Furnham, 2009). These included intelligence, stability, conscientiousness, height, education, social skills and compatibility in terms of politics and religion. For men, physical appearance was more important than it was for women. Men and women were more likely to like a mate who shared similar personality characteristics such as extraversion and conscientiousness.

Question 34

Perils of being beautiful

Answer 34

• Is there a disadvantage to being very attractive? Research suggests that there is. If female students are asked to judge the suitability of an attractive, average and unattractive man as a long-term partner in a lonely heart advertisement implying high, medium or low socioeconomic status (SES), who do you think the women chose?
• If you said high-status, attractive men, you would be wrong. If you had said attractive men of medium status, you would be right. Why? According to the authors (Chu et al, 2007) the women regarded attractive, high-status men as pursuing a mating strategy (simply put, they were after sex), rather than a parenting strategy (wanting to settle down). High-status, attractive men would be far more likely to be the recipient of other women’s attention (and, therefore, be at greatest risk of yielding to this attention). Women – well, UK undergraduates – it seems, do not want Mr Perfect, just Mr Almost Perfect.
• Physically attractive men have also been found to increase financial risk-taking in other men (Chan, 2015). The reasoning behind this is that a man who is in competition with a more physically attractive man will attempt to increase his desirability by gambling more money with a view to gaining more money.
  Women might also settle for Mr Average. In one study, women engaged in speed-dating were asked how important they thought a man’s physical attractiveness and earning prospects were (Eastwick and Finkel, 2008). When asked to consider an ideal partner, these features were considered important. However, this preference did not predict their mate choice at the dating evening, neither did it predict their choice of real-life partners when the researchers contacted them after the study.

Question 35

One theory of attractiveness suggests that we choose a mate who is similar in attractiveness to ourselves

Answer 35

This is called the matching phenomenon (Walster et al, 1966), but no model can explain this satisfactorily.
* Is it because we are more anxious or insecure, or fear rejection or have low self-esteem? Some social psychologists argue that we view others through our own egotistical lens. ‘The self provides the frame of reference from which all else is observed’, state Combs and Snygg (1959). ‘People are not really fat unless they are fatter than we’. This would suggest that our ratings of others’ physical attractiveness are affected by our assessment of our own physical attractiveness (whether this view is shared by others or not).
* Montoya (2008) found that participants’ ratings of another person’s attractiveness decreased with the increasing, objective, physical attractiveness of the rater. People rating themselves moderate in attractiveness paired themselves with people they thought were attractive.
* There is support for his finding. One study found that people rated their partners as being significantly more attractive than themselves; there was no difference between men or women (Swami et al, 2009). People are also more likely to administer surveys to their peers if they have been paired with an attractive rather than unattractive individual and are more likely to administer surveys to older people if they are paired with unattractive people (Winegard et al, 2013).
* In terms of long-term satisfaction with their partners, the research regarding frequency of sex and relationship satisfaction is inconsistent, but a recent three-year study of newlyweds found that there was a significant positive relationship between sex frequency and partner evaluations but not relationship satisfaction (Hicks et al, 2016).
* Jonason et al (2015) have noted that few studies have investigated directly what you might call dealbreakers (what to avoid in a potential partner) rather than dealmakers (what we find desirable). In a set of six studies involving 6,500 participants, the researchers found that such dealbreakers included undesirable personality traits, unhealthy sexual and romantic relationships, and dubious friendships. These were considered to be far more important when considering long-term relationships in men and women and more important to women in short-term relationships. People who were highly desirable (personally, physically, financially) were more likely to have more dealbreakers when considering a relationship. People who were less restrictive about their sexual behaviour, had fewer.
Men and women respond to strangers in different ways, especially if the strangers are responsive. Birnbaum et al (2014) found that men regarded women who were responsive to an approach to be more feminine than those who did not respond. Men also found those women to be more sexually arousing (and more attractive and more likely to be seen as a potential partner). It does make you think twice about speaking to someone on the bus.

Question 36

Monogamy - shared, but not always equal, parental investment

Answer 36

• Around 3 per cent of the relationships in mammals are monogamous.
• Monogamy has evolved in those species whose environments have favoured the contributions of both parents to the survival and reproductive success of their offspring.
• In other words, under some conditions, two individuals sharing parental duties enjoy more reproductive success than does one individual who must do it all alone.
• Although both parents in monogamous species share offspring-rearing duties, each parent may not make an equal contribution towards that end.
• Like females in polygynous species, females in monogamous species generally have greater parental investment in the offspring, for many of the same reasons: the limited opportunity for mating relative to that for males, pregnancy and its accompanying risks, providing milk to the newborns, and the time and energy spent in caring for them. As a result, very few monogamous species, including our own, are exclusively monogamous.
  In fact, there is a strong tendency in most monogamous species towards patterns of reproductive behaviour and parental investment that resemble those of polygynous species. For example, in monogamous species, females tend to be more careful than males in selecting a mate, and males tend to be more sexually promiscuous than females (Badcock, 1991).

Question 37

Monogamy and hormones

Answer 37

• Some scientists have hypothesised that monogamy may be attributable to chemicals called hormones (Young et al, 1998). These are generated by a region in the brain which sends signals to organs of the body to react in a certain way. The proposed relationship between hormones and monogamy has been based on studies of a type of rodent, the vole.
  Researchers have found that two types of vole show very different patterns of mating: the prairie vole is largely monogamous, forming lasting partnerships; the montane vole, however, is promiscuous and not a particularly social species. The male montane vole is not parental and does not form a bond with its partner; the female montane vole abandons its offspring around two to three weeks after birth (Young et al, 1998).

Question 38

Are specific body types universally attractive?

Answer 38

• In the developed world, physically attractive women are considered to be those with a low WHR and men are regarded as more attractive if they have the inverted A-frame (broad shoulders and relatively slimmer waist). The apparent universal preference for women with low WHR would seem to support sociobiology’s argument that mates are selected for their health and fitness. But does it?
• Yu and Shepard (1998) compared the body shape preferences of American men and men from the Matsigenka people in south-east Peru. The Matsigenka’s culture is basically agrarian: they engage in slash and burn agriculture and supplement this food production with game and fruit gathered using traditional tools. None had been exposed to Western civilisation (no television, film, newspapers, and so on). Whereas the Western sample predictably preferred those females with low WHR, the Matsigenka men preferred overweight females and those with high WHR, rating these as the more attractive, healthy and desirable as a spouse.
• In a similar study, Frank Marlowe and Adam Wetsman, two American anthropologists, found that whereas American men in their study preferred a low WHR and especially liked the intermediate image showing a WHR of 0.7, Hadza men, a group of hunter-gatherers who inhabit mixed savannah woodland in Tanzania, preferred a higher WHR (Marlowe and Wetsman, 2001).British and Malaysian participants, however, are less enamoured of WHR (Swami and Tovee, 2005a). The researchers asked 682 participants to rate the photographs of real women.
  The study found that those who lived in urban areas preferred lower BMIs than did those living in the country, perhaps reflecting the greater exposure of urbanites to slimmer women. People who lived in urban areas also preferred men with low WCR (BMI or WHR were not good predictors) (Swami and Tovee, 2005b). In rural areas BMI was the primary predictor of attractiveness. Urban raters preferred men with an ‘inverted triangle’ shaped torso, whereas rural raters preferred heavier men with a less triangular shape.

Question 39

Swami and colleagues reported an interaction between WHR and breast size.

Answer 39

South African men preferred high-WHR black figures with large breasts and high-WHR white figures with small breasts, whereas white British men and British Africans preferred high-WHR black figures with small breasts and high-WHR white figures with large breasts (Swami et al, 2009).
* A cross-cultural study of WHR preference in participants from Africa, Indonesia, Samoa and New Zealand has confirmed the universal trend: participants rated women low in WHR as being more attractive (even when BMI was controlled for) (Singh et al, 2010).
* One study has even extended this preference to the blind. Researchers from the USA and the Netherlands asked 19 men who had been blind since birth to rate their preference for the body shape of mannequins whose WHR could be manipulated (Karremans et al, 2010). The men did this by touch. They preferred figures with a low WHR. When sighted men performed the same task, the same effect was found but the preference was stronger.
* Finally, one of the largest studies of its kind examined female body preferences of 7,434 respondents from 26 countries, grouped into 10 regions drawn from North America, South America, Western Europe, Eastern Europe, Scandinavia, Oceania (Australia, New Zealand), Southeast Asia, East Asia, South and West Asia and Africa (Swami et al, 2010). Respondents from Eastern Europe, Scandinavia and Western Europe preferred heavier figures. There were significant differences between rural and urban sites in Malaysia and South Africa. The ideal body weight was heavier in societies that were less socially and economically developed.
Apart from East Asian men, other men chose a heavier figure as their preferred shape than did women, thereby highlighting a disparity about what women perceive as the ideal body shape preferred by men and men’s own actual preference. ‘Such misinterpretation of men’s standards of bodily attractiveness on the part of women’, Swami et al conclude, ‘may be near universal in contexts of high SES’ (p. 320).

Question 40

One reason for the disparity may be that the media to which men are exposed feature curvier women whereas women’s media idealise the thin.

Answer 40

• American women expressed greater body dissatisfaction than women from any other region. At another level, individuals of low SES in Malaysia and South Africa also expressed low levels of body satisfaction. A correlation was found between exposure to Western media and preference for a thinner body type.
  While a low WHR is considered the more appealing body shape in a large part of the world, even when controlling for weight, there are specific cultures and nations – although not many – which express a different preference.

Question 41

Two key hormones have been identified that could underpin these behaviours: oxytocin (OT) and vasopressin (AVP).

Answer 41

• In prairie voles, vaginal–cervical copulation leads to an increase in the release of OT. This release may promote intense mating in females but has little effect on males. AVP, however, does affect male prairie voles. Administering this hormone in these male voles leads to a preference for an exclusive partner, aggression towards strangers and an increase in paternal care (Young et al, 1998). In the montane male vole, the effect of the hormones is not aggression but self-grooming. The receptor distribution for these hormones in the brain of the prairie vole is similar to that in other monogamous types of vole; conversely, the distribution of receptors in montane voles is similar to other promiscuous vole types.
• Some research has found that when people are exposed to oxytocin, their caring behaviour, parental bonding and trust increase. For example, intranasal administration of the chemical has been found to increase maintained eye contact during relationship conflict resolution (Ditzen et al, 2009), sensitivity to others’ feelings (Hurleman et al, 2010), generosity (Barraza and Zak, 2009) and results in judgements of faces presented on a computer monitor to be more trustworthy and friendly, compared with those who did not receive the hormone (Theodoridou et al, 2009).
• A meta-analysis of brain imaging studies of the effect of oxytocin on social and emotional processing found greater activation in the left insula during these types of processing which might suggest that the effect of oxytocin is modulated via this brain region (Wigton et al, 2014).
• Kisspeptin is a recently discovered reproductive hormone which has been found in the limbic system of rodents and humans.
• Comninos et al (2017) examined the effect of intravenous kisspeptin on sexual arousal in 29 healthy heterosexual men. They found that men who had received kisspeptin and were exposed to sexual images, showed an increase in activation in the limbic system, especially in the anterior and posterior cingulate and left amygdala. The greater the activation in the limbic system during kisspeptin administration, the less likely the men were to be averse to sex.
  Recent research has begun to cast doubt on the reliability and validity of some of the behavioural findings in oxytocin research. The Controversies in psychological science section takes up the issues.

Question 42

Infidelity

Answer 42

• For various evolutionary reasons, evolutionary psychologists suggest that men and women respond differently to different types of infidelity. Heterosexual men, for example, are more likely to show jealousy in response to sexual infidelity (a partner having sex with another man), whereas heterosexual women are more likely to show jealousy in response to emotional infidelity (a partner having a very deep, loving, yet non-sexual, relationship with another woman).
• A study in which male and female undergraduates were asked whether they would forgive the two types of infidelity in their partner conformed to the expected pattern and found that men were less likely to forgive sexual than emotional infidelity, whereas women showed the opposite pattern (Shackelford et al, 2002). Men were also more likely to terminate a relationship if their partner committed sexual infidelity. They are also more likely to be more accepting of same-sex infidelity than are women: that is, they are more accepting of a female partner being unfaithful with a woman (Wang & Apostolou, 2019).
• Harris (2002) found that heterosexual men were more likely to find sexual infidelity more upsetting than they would emotional infidelity. The reverse pattern was found for women. When participants recalled actual examples of infidelity, however, no sex differences were found. Regardless of sexual orientation, both men and women were more likely to focus on a partner’s emotional than sexual infidelity as the source of distress. No relationship was found between participants’ responses to hypothetical and actual infidelity.
• A study which compared differences between homosexual and heterosexual in terms of the type of infidelity they felt caused more distress found the predicted pattern in heterosexual samples (de Visser et al, 2019). However, gay and bisexual men were more likely to experience greater jealousy to emotional infidelity than were bisexual women or lesbians.
  A recent cross-cultural study explored women’s reactions to opposite-sex or same-sex infidelity in three groups: from Canada, Samoa and Istmo Zapotec (Semenya et al, 2021). Two of these cultures also include examples of masculine men engaging in relationships with feminine third-gender men. The Canadian undergraduate samples reported being most upset by infidelity with an opposite-sex partner, but a community sample of middle-aged women were equally upset by heterosexual or homosexual infidelity. Samoan women were more likely to be upset at infidelity with a woman than a third-gender male. One Zapotec sample reported being equally upset by infidelity with a woman or third-gender male, whereas another sample found greater upset at infidelity with the third-gender men.

Question 43

What makes a person poach or steal another’s partner?

Answer 43

• One study found that 84 per cent of undergraduates reported that attempts had been made to poach them from their partners (Schmitt and Buss, 2001). Of those who were romantically linked (just over 55 per cent), 20 per cent of men and 28 per cent of women stated that their partners had been poached from someone else. In terms of personality, agreeable and conscientious people were least likely to be mate poachers, a finding that is found internationally (Schmitt, 2004).
• Those who did not regard relationships as exclusive and described themselves as having erotophilic tendencies – a constant desire to satisfy sexual needs – were more likely to poach. These individuals also scored high on sexual attractiveness: it appears that the poacher may have to be sexy, as well as adulterous. Extraverts were more likely than introverts to be recipients of poaching attempts. Those who rated themselves as sexually attractive, as not relationship exclusive and as emotionally investing (loving) were those who were most likely to be poached.
• Physical attractiveness was more important for men than it was for women. Women, conversely, were more likely to view resource acquisition as a benefit of poaching, especially in short-term relationships. Because men value physical attractiveness in women, women pay greater attention to using physical characteristics as cues to attraction. Women, on the other hand, placed greater value on resources. Men, consequently, emphasised cues that indicate that they were resource-laden (such as having expensive clothes, cars, jewellery, and so on). For women, a strategy aimed at making themselves more attractive by disparaging the partner of the person they wanted to poach was not as effective as one based on enhancing their own physical attractiveness.
• As predicted, men were found to be more successful than women at poaching when they displayed resources and were more effective at using humour as a poaching cue than were women in the short and long term. Women employed a tactic that was significantly more effective when used by them than by men: boosting the partner’s ego.
• Davies and Shackelford (2015, 2017) in a study of undergraduates, found that participants were more likely to be poached if the poacher was wealthier and more attractive than the partner whom they were dating, living with, or were married to. The more committed to the relationship the person was, the more attractive and wealthier the poacher had to be.
• Another study found that people who were more likely to enjoy short-term relationships also had lower levels of sexual disgust (Al-Shawaf et al, 2014).
• Mate poaching might have neural correlates. Ueda et al (2016) asked 33 Japanese men to look at photographs of attractive women who had a partner, attractive women who did not have a partner, unattractive women who had a partner and unattractive women who did not have a partner. A neuroimaging technique recorded brain activation while participants made judgements about how likely they were to want a romantic relationship with the woman.
  Men were more likely to want a romantic relationship with an attractive woman than an unattractive one (no surprise there) – and this decision was associated with activity in a part of the brain known as the ventral striatum. They also found the women with a partner to be romantically less desirable and this decision was associated with activation in the parietal lobe. Men who showed greatest activation in the tip of the front part of the brain called the orbitofrontal cortex (OFC) were more likely to indicate that they would like to engage in a romantic relationship with a woman who had a partner. The researchers conclude that ‘the OFC is a critical region that reflects individual differences in mate poaching, with those showing higher OFC activity assigning increased value to a female with a partner’ (p. 7) (In 33 Japanese men, of course).

Question 44

Jealousy

Answer 44

• Jealousy has been defined as ‘when individuals perceive a threat to their relationship because of an actual or imagined rival’ (Massar and Buunk, 2010, p. 634).
• Although romantic jealousy seems more common in men than in women, the sexes may also differ in what provokes jealousy.
• Men are more likely to be jealous, angry and upset about sexual infidelity, whereas women are more likely to be upset by emotional infidelity, such as their partner engaging in a warm and fulfilling friendship with another woman (Sagarin et al, 2012).
• Sex differences in jealousy have been reported worldwide and in countries such as Germany, Korea, the Netherlands, Japan, Brazil, Romania, the UK, the US, Norway, Spain and others (Buss, 2013).
• Some researchers have suggested that these differences might have a neural basis. Takahashi et al (2006), for example, asked men and women to think about jealousy-arousing sentences such as ‘My girlfriend stayed in a double-bed room in a hotel with her ex-boyfriend’ and ‘My girlfriend had her underwear taken off by another man’ (sexual jealousy items) or ‘My girlfriend wrote a love letter to another man’ and ‘My girlfriend gave gorgeous birthday presents to her ex-boyfriend’ (emotional jealousy items) as well as neutral statements about their partner. The groups did not differ significantly in terms of the types of infidelity they felt jealous about; both sexes became equally jealous under both conditions (emotional or sexual infidelity). However, brain activation did differ by sex.
• Men showed greater activation in the amygdala during sexual jealousy and in the hypothalamus during emotional infidelity. These are structures involved in sexuality and reproduction, among other functions. Women showed greater activation in the posterior superior temporal sulcus (STS), an area the authors suggest is implicated in ‘the detection of others’ intention or violation of social norms’.
  Is it easy to induce jealousy? Massar and Buunk (2010) exposed 40 young women to photographs of attractive or unattractive women for 60 minutes. They then asked them to rate how jealous they felt when told to imagine placing themselves in a scenario designed to elicit jealousy (a rival being introduced to their partner). The researchers found that women who were exposed to attractive women reported significantly more jealousy than did those exposed to the unattractive ones, suggesting that jealousy may be primed or elicited unconsciously.

Question 45

Promiscuity

Answer 45

• Promiscuity – the tendency to engage in sexual activity with multiple partners (not necessarily at the same time) – has been associated with specific personality types. Sensation-seekers, for example, have more partners than low sensation-seekers; and the unconscientious, extravert, the less agreeable and more antagonistic similarly report having more sexual partners than the conscientious, the less extravert and the more agreeable/less antagonistic.
• In a study of 105 young men and 105 young women, people who were dominant had significantly more sexual partners than did those who were less so (Markey and Markey, 2007). Curiously, people who were personally warm were also more likely to have had more sexual partners than the less warm.
  A related study examined whether men who engaged in unrestricted sexual activity – engaging in transient sexual relations – perceived women’s attractiveness differently from men who were more restricted (Swami et al, 2008). Men self-described as restricted or unrestricted rated the attractiveness of drawings of women who differed according to BMI and WHR. The men, regardless of type, used BMI rather than WHR as the basis of their judgement, but unrestricted men found women with lower BMI to be more attractive and healthier than did restricted men. The unrestricted men also preferred women with a low WHR.

Question 46

Altruism and kin selection

Answer 46

A particularly interesting and important social behaviour in terms of evolution is altruism, the unselfish concern of one individual for the welfare of another. Examples of altruistic behaviour abound, and its most extreme form is when one person risks their life to save the life of another. Examples of altruism are also common throughout the animal kingdom. The honey bee, for example, sacrifices its life on behalf of its hivemates by stinging an intruder. Here, the altruist’s chances of survival and reproductive success are lowered, while those of the other individuals are raised.
Sociobiologists seek out ultimate causes, especially the consequences of natural selection, to explain altruism. They assert that natural selection has favoured the evolution of organisms that show altruistic tendencies. However, there is an important problem here. On the surface, altruism poses an enigma to evolutionary theory. Recall that according to natural selection only phenotypes that enhance one’s reproductive success are favoured. How could altruistic behaviour have evolved given that, by definition, it is less adaptive than selfish or competitive behaviour?
The geneticist William D. Hamilton (1964, 1970) suggested an answer to this question in a series of mathematical papers. Hamilton’s ideas stemmed from examining natural selection from the perspective of the gene instead of from the perspective of the whole, living organism. He argued that natural selection does not favour mere reproductive success but rather inclusive fitness, or the reproductive success of those individuals who share many of the same genes. Altruistic acts are generally aimed at close relatives such as parents, siblings, grandparents and grandchildren. The closer the family relation is, the more likely the genetic similarity among the individuals involved. Such biological favouritism towards relatives is called kin selection (Maynard Smith, 1964).
The message here is clear: under the proper circumstances, individuals behave altruistically towards others with whom they share a genetic history, with the willingness to do so decreasing as the relative becomes more distant. In this view, altruism is not necessarily a conscious act but rather an act driven by a biological prompt that has been favoured by natural selection. Natural selection would favour this kind of altruism simply because organisms who share genes also help each other to survive.

Question 47

Parenting is a special case of kin selection and an important contributor to one’s survival and reproductive success

Answer 47

n the short run, parents’ altruistic actions promote the continued survival of their offspring. In the long run, these actions increase the likelihood that the offspring, too, will become parents and that their genes will survive in successive generations. Such cycles continue according to biological schedule, generation after generation.
What is at stake is not the survival of individual organisms, but the survival of the genes carried by those organisms. Genes allow organisms to maximise their inclusive fitness through altruistic behaviour directed at other organisms sharing the same genes. Inclusive fitness refers to the idea that reproduction and natural selection occur because an individual’s success is measured through the production of offspring. You carry copies of genes that have been in your family line for thousands of years. When the opportunity presents itself, you will most likely carry on the tradition – reproducing and thus projecting your biological endowment into yet another generation. But you did not reach sexual maturity on your own; the concern for your welfare by your parents, brothers, sisters, grandparents and perhaps an aunt or uncle has contributed to your chances of being reproductively successful. Genes not projected into the next generation simply disappear.
Another variable may mediate altruism, however: emotional closeness. Emotional closeness is defined as having a sense of concern and caring for another and enjoying a comforting, emotional relationship with them. One study asked participants to rate how willing they would be to behave altruistically towards members of their family when the family member could live or die, and when helping would be at a cost to the participant (Korchmaros and Kenny, 2001). Participants also indicated how emotionally close they were to these family members.

Question 48

People were more likely to help family members with whom they shared a close relationship, regardless of the genetic closeness of the relationship, than those with whom they shared a less close relationship

Answer 48

The findings suggest that emotional closeness may be a mediating cause of altruistic behaviour. Altruistic tendencies also increase across the lifespan (Sparrow et al, 2021).
Evidence from step-relations’ behaviour supports the idea of inclusive fitness. It has been reported, for example, that a disproportionate number of children in stepfamilies suffer physical harm, especially assault (Daly and Wilson, 1988). Child battering is more common in stepfamilies, as is the incidence of child abuse (Daly and Wilson, 1996). This evidence, the sociobiologists argue, supports the notion that non-genetic relatives are not disposed to invest resources in offspring that are genetically unrelated.

Question 49

How sexually attractive is intelligence?

Answer 49

In a very well-known (in psychology circles, at least) study of the partner characteristics people found most desirable, the features ranked as most valued were being kind, understanding and intelligent (Buss et al, 1990). A study of male and female students, led by the person who authored the 1990 study, found a similar result: intelligence and education were regarded as the most important of 13 partner characteristics (Buss et al, 2001). Others have examined the degree of intelligence people prefer. (Kenrick et al, 1990). For example, for a single date, average intelligence was enough but for marriage, partners required a greater degree of intelligence. Women expected increased intelligence with increased investment in a relationship (dating, sex, steady dating, marriage); men, however, expected more intelligence from dating than sex and higher intelligence from steady dating and marriage.
If we do consider intelligence to be desirable in a partner or ‘mate’, is there a maximum desirable level? Research suggests there might be and this is an IQ of around 120. Beyond this, other variables become important (such as personality). People who do find individuals with high IQs to be sexually attractive do not value others for the benefits of having an IQ (although they might); they find their intelligence sexually exciting. One hypothesis derived from this is that women at different points of their menstrual cycle would find different degrees of intelligence more attractive (such as during the more fertile part of the cycle). Evidence is mixed, although Haselton & Miller (2006) in a study with a small sample found that when women were at their most fertile, they regarded creatively intelligent men as more attractive than rich men.
To examine whether intelligence was associated with sexual attraction and with interest in a long-term partner, Gignac et al (2018) asked 383 first year students and participants recruited via Mechanical Turk to complete a variety of measures including a partner preference scale, an intelligence attraction/interest scale, a scale measuring sapiosexuality and measures of cognitive ability. The second of these took the form of seven statements to which participants responded with the degree of attraction they would express. The statements were ‘how interested would you be in [a] person as a potential partner. . . if they were smarter than 1%/10%/25%/50%/75%/90%/99% of the population’ (thus the seven percentage categories provided seven statements).
As predicted from some of the previous research, an IQ of 120 was regarded as being the most desirable in terms of sexual attraction and in terms of forming a long-term relationship. A very high IQ (>135) was not regarded as sexually attractive and you can speculate, based on some of the research reviewed in this chapter, why that might be.

Question 50

Reciprocal altruism

Answer 50

Kin selection explains altruism towards relatives, but what about altruism directed towards non-relatives? According to Trivers (1971), this kind of altruism, called reciprocal altruism, exists because humans (and other organisms) can function more effectively if they work together. Human groups are hierarchical and cooperative (Buss, 1995), whether at the level of the family, canoe club or workplace. There is also evidence that kindness, dependability, emotional stability and intelligence (all traits one would associate with altruism) are the most valued personality characteristics in potential mates (Buss, 1995). Cooperation between groups is a fundamental survival strategy (Brewer and Caporael, 1990), and is seen in many higher primates (Byrne, 1995). For example, in order to win a mate from a dominant male savannah baboon, a male will engage the help of another baboon who will distract the dominant male and enter into a fight with him. This leaves the other, non-dominant male free to mate with the female. The altruism is reciprocal because the favour will be reciprocated by the successfully paired male in the future (Haufstater, cited in Byrne, 1995).

Question 51

Evolutionary psychology/sociobiology - issues and controversies

Answer 51

• Sociobiology attempts to explain social behaviour through natural selection and genetic inheritance but it has been the centre of a fierce scientific controversy ever since E.O.
• Wilson’s book, Sociobiology: The new synthesis, marked the official birth date of the discipline in 1975.
• Wilson’s book, On Human Nature (2004), extended sociobiological theory to human affairs and sparked even more criticism.
• Most of the criticism focuses on the extension of the theory to human behaviour. Two issues that have caused great controversy are inclusive fitness and the mechanisms of adaption.
• Inclusive fitness theory argues that reproduction and natural selection occur because an individual’s reproductive success is measured through the production of offspring. Those characteristics which help promote the transmission of genes (either directly or indirectly) will be naturally selected simiarly to darwins seive.
• Sociobiologists see humans as “fitness maximisers” or “fitness strivers” (Alexander 1979) constantly applying mechanisms for maximising inclusive fitness.
• Evolutionary psychologists however call this The “sociobiological fallacy” (Buss 1991,1995) because it confuses the theory of origins of mechanisms with the theory of the nature of mechanisms. We can look at individuals or their behaviour and easily find maximising fitness reasons for this behaviour. Therefore, The inclusive fitness theory cannot account for natural selection and is virtually limitless in its application due to its breadth.
• Evolutionary psychologists see humans as “adaptation executors” or “mechanism activators”. (Tooby and Cosmides, 1990). Humans apply evolved solutions for adaptive problems, (Buss 1995) which are specific to different domains. The types of solution would need to reach to select a mate are different from those needed to obtain food or to parent children.
• Adaptive problems are large, complex and varied - the success of individuals in solving these problems depends on sex, species, age, context and individual circumstances (Buss et al 1998). Sociobiology overlooks this psychological level of interpretation and goes from evolution straight to patterns of social organization.
• Sociobiology has faced political criticism for allegedly promoting the superiority of one group over another be it race, gender or a political organisation. They argue, if one group of individuals is genetically superior to another, then there are ‘natural’ grounds for justifying the ‘survival of the fittest’ and one group’s unethical and immoral domination of another.
  but sociobiologists reject these claims and argue that it’s the critics not them that have confused the term ‘natural’ with the terms ‘good’ or ‘superior’. It raises the question of whether political objections to sociobiology are scientifically valid and whether psychologists should consider political objections to their findings or theories.

Question 52

Does evolutionary psychology have a sex bias?

Answer 52

• Evolutionary psychology has been criticized for its WEIRD issues. In a review of the 2015-16 volumes of the journals evolution and human behaviour and evolutionary psychology - 81% of 113 samples come from Western countries and only 12% from Asia and 14% from Africa, Latin America or the Caribbean.
• There is a sex bias in evolutionary psychology as it is dominated by one sex. In a review of sex bias in evolutionary psychology texts it found that most discussed female attractiveness and neglecting other traits such as intelligence and resourcefulness, over-emphasised men’s ability to feed families, and neglected older women (Burch, 2020). Less than one page is spent on older women, past the menopause.
• 14/18 texts were solely written by men. When women were authors, traits other than a women’s attractiveness were described and discussed.
  A study asked people whether they endorsed evolutionary psychology theories abut mate attraction. Ward et al (2021) hypothesised that those who would be most privileged by these theories eg physical attractiveness leading to greater mate attraction, would be more likely to endorse them. That is what they found. In two studies people who are perceived as physically attractive are more likely to endorse evolutionary principles related to mate attraction.