3. Variation and life history

Question 1

what is the term ‘father absence’ generally taken to indicate?

Answer 1

generally taken to indicate that an individual has spent some or all of their childhood with a nonresident biological father. While this can be due to paternal death, the majority of research concentrates on cases of nonresident fathers who are separated from (or were never pair bonded with) the individual’s mother

Question 2

why is there an interest in puberty onset?

Answer 2

There is extensive variation in the timing of puberty across human populations, raising questions about the causes of these differences

Question 3

what has father absence been shown to increase in terms of development. And what does this result in?

Answer 3

Early father absence (potentially among other stressors) may accelerate pubertal development and the onset of sexual behavior in daughters as a response to environments which were unstable and/or unlikely to support viable pair-bonds. As such, maximizing reproductive success might best be achieved, for girls, by starting reproduction earlier (Belsky et al. 1991)

Question 4

study support for absent father causing menarche

Answer 4

Webster et al. (2014) published a meta-analysis of this literature suggests that approximately 5.6 % of variance in age of menarche may be explained by the presence or absence of the biological father from the home in early childhood.

Question 5

evidence for absent father causing earlier sexual activity

Answer 5

Alongside earlier menarche, father absence in Western samples is also typically associated with earlier sexual activity and earlier reproduction in women (e.g., Ellis et al. 2003; Boothroyd et al., 2013)

Question 6

what is the current explanation for stress/ paternal absence on menarche

Answer 6

The dominant current explanation for these phenomena focuses on the influence of stress on the maturation of the endocrine system (see, e.g., Ellis 2013)

Question 7

what is the key factor from either perspective model of fitness benefits post stress/ father absence

Answer 7

The key factor from either perspective is that father absence may trigger earlier menarche and earlier reproduction as a means of maximizing reproductive success when faced, in some form, with harsh environments.

Question 8

why is the timing of reproductive maturity so important to study?

Answer 8

the timing of reproductive maturity is considered a key developmental decision point, since it is the transition at which an organism’s priorities shift from growth to reproduction (Hill & Kaplan, 1999).

Question 9

what is life history theory?

Answer 9

a branch of evolutionary theory developed to explain the ex-tensive variation in life cycle timing and reproductive strategies across mammalian taxa (Stearns, 1992).

• The study of how and why organisms vary in their prioritisation of different goals in energy expenditure

Question 10

what does LHT predict about mortality and what would we expect from this?

Answer 10

Because high extrinsic (unavoidable) mortality increases the risk of dying before reproducing and leads to discounting of future fitness, prominent LHT models assume that mortality is a key determinant of variation in the optimal age of maturity across species

Question 11

evidence for LHT and mortality

Answer 11

As a particularly salient cue of harshness, direct experience of a heightened mortality risk—such as through the death of a parent or sibling—have also been shown to predict accelerated maturation and earlier onset of reproduction (Chisholm, 1993; Ellis, et al, 2009). These findings have been interpreted as evidence that individuals can selectively adopt a “faster” life history when local conditions signal an uncertain or predictably harsh future

Question 12

what is the big issue with many studies into menarchy and LHT

Answer 12

Although many studies generally support the expectations of this LHT-inspired model, it is notable that the majority of studies investigating links between psychosocial stress, environmental risk, and pubertal timing have focused on populations living in high-income, low-fertility countries in which the maturation-accelerating effect of over-nutrition and overweight are common (Anderson, 2015; Sohn, 2017).

Question 13

what has been suggested may play a more vital role than mortality/ paternal absence?

Answer 13

nutrition and calorific intake

Question 14

talk about menarche in northern european countries

Answer 14

Studies have demonstrated a roughly four to five year decline in age at menarche in northern European countries with good historical records, from a mean of approximately 17 years of age in the mid 1800s to a recent mean of 12.5 in wealthy nations (Konner,2010)

Question 15

menarche in lower and middle income countries when does earlier menarcheal age occur?

Answer 15

documented in many lower and middle-income countries, and earlier menarcheal age is also characteristic of individuals of higher socioeconomic status within populations (Parent et al., 2003)

Question 16

what have findings on menarcheal age changing in terms of wealth indivate

Answer 16

Traditionally, these findings have been interpreted as a reflection of improvements in nutrition and control of common early life infections, which led to a more rapid pace of growth and an earlier onset of puberty and reproductive maturation

Question 17

what have studies which have studied the effects of family instability and psycho social stress in populations with less abundant nutrition

Answer 17

studies in populations faced with less abundant nutrition generally find that psychosocial stress and familial instability are not predictive of earlier maturity for females (Anderson, 2015; Sheppard et al., 2014)

Question 18

main study on nutrition and life history theory what did they do?

Answer 18

Kyweluk et al., 2018

Used cohort of women from Cebu Longitudinal Health and Nutrition Survey – following a large group in the Phillipines from birth into middle adulthood.

Question 19

what did the main study on LHT find?

Answer 19

Kyweluk et al., 2018

Found that measures of early life adversity or familial instability—as reflected in paternal absence, maternal absence or sibling death—did not predict maturational tempo. Instead, measures reflecting favourable infancy and childhood nutrition and growth were strong predictors of maturational acceleration.

Question 20

what do the findings or Kyweluk et al., 2018 run counter to?

Answer 20

findings run counter to the expectations of psychosocial models of maturational acceleration derived from life history theory, and suggest that in contexts like Cebu nutritionist likely the primary determinant of pubertal timing, with more favourable nutrition leading to earlier menarche

Question 21

conclusion on nutrition and LHT

Answer 21

the conclusive nature of work in this field suggests that nutrition may serve as more of a cue than stress. And whilst something to do with stress may be going on what seems clear is that when psychosocial stress is accompanied by some degree of nutritional stress, the maturation-slowing effect of poor nutrition will overcome any more modest accelerating effect of psychosocial stressors and lead to an overall delay in maturation in high stress settings, much as we see at Cebu.

Question 22

what can be said about LHT put into modern societies in terms of menarche and sex

Answer 22

From the perspective of human evolution, the co-occurrence of caloric abundance alongside stress related to ecological harsh-ness is likely a recent phenomenon unique to the rise of wealthy countries with pronounced income inequality; such environments, in which major psychosocial stressors may occur in the absence of energetic growth constraint, have the potential to inflate the apparent im-portance of developmental stressors as accelerators of maturational timing (Kuzawa & Bragg, 2012)

Question 23

father absence in males for reproduction and puberty

Answer 23

• Reproduce earlier in western samples (Jaffee et al., 2001)
• Results are decidedly mixed- some have found father absence to predict later puberty in males (e.g. Sheppard et al., 2015)

Question 24

what are males with no fathers likely to go on to be?

Answer 24

• Father absent boys are more likely to go on to be absent fathers themselves (e..g Jaffee et al., 2001)

Question 25

what have researchers argued about sex differences in father absence for males

Answer 25

Several authors have argued that a sex difference in responses to father absence is consistent with sex differences in predictors of reproductive success, with males perhaps benefiting most from building competitive advantage rather than accelerating reproduction in harsh and/or low-paternal-investment environments (e.g. James et al. 2012).

Question 26

what does behavioral ecology focus on?

Answer 26

offspring outcomes in terms of survival and fertility- drivers of parenting behaviour rather than drivers of child development

Question 27

does father absence or presence have an effect on offspring fertility?

Answer 27

Seems that father absence (or presence) often makes little difference to offspring at all Wide-ranging systematic review (Sear and Coall, 2011)

Question 28

Who conducted a review of father absence in fertility and what did they find?

Answer 28

Sear and Coall, 2011 * In WEIRD (low-fertility) samples the presence of fathers appeared to have an inhibitory effect on fertility (indexed by less teenage pregnancy, later first birth) * fathers in high-fertility samples had a facilitatory or no effect on offspring fertility. * Where there were significant associations, present/living fathers were typically associated with earlier first birth and a greater number of children born, the former of which is directly at odds with the data from Western samples.

Question 29

what seems the most likely explanation for Sear and Coall's findings?

Answer 29

Perhaps the most likely explanation for these results is that in small-scale and high-fertility populations, the most critical contribution of secondary caregivers (as fathers tend to be) is to supplement the child’s nutritional or social status in a manner which makes a much greater contribution to maturation and/or marriageability than any variation induced by psychosocial stressors.

Question 30

why should we raise the question on how much we can infer from Weird samples

Answer 30

Indeed the simple fact that girls in WEIRD samples display considerably earlier menarche than in small-scale societies suggests that considerable nutritional constraints on menarche have been lifted in the West and, as such, raises the question of how much these WEIRD samples can tell us about ancestral selection pressures on reproductive development

Question 31

what unites both behavioral ecology and developmental psychology?

Answer 31

Mortality and morbidity outcomes in offspring --> interest in how paternal care/ stress may influence offspring viability and condition

Question 32

support that father absence influences well being of offspring

Answer 32

There are a number of large epidemiological studies in the West which find an association between parental divorce (usually synonymous with father absence in these data) and poorer adult health, shorter adult height, and shorter life expectancy in offspring (Sheppard et al. 2015). In some samples, the associations between family structure and later offspring outcomes were mediated by stressors inherent in, or other sequelae of, the separation (e.g., Maier and Lachman 2000), which is consistent with other evidence suggesting relational stress in childhood may be associated with health outcomes in later years.

Question 33

what is different to data on offspring health and wellbeing compared to reproductive data

Answer 33

these associations are not limited to WEIRD samples.

Question 34

who studied offspring viability/ health in non-western sample give background to study.

Answer 34

Flinn and England (1997) assessed the living conditions of children and adolescents living in a village in Dominica took regular saliva samples (several times a day for multiple days) to assess their levels of cortisol (a stress-related hormone) and monitored children’s health. The population they studied was matrilocal and the parenting conditions were very varied; approx half of children were living with their mother and their biological or stepfather, while a further 12 % lived alone with a single parent. The remainder of the children lived with mother and kin, grandparents, distant kin or nonrelatives.

Question 35

who studied offspring viability/ health in non-western sample what did they find?

Answer 35

Flinn and England (1997) assessed the living conditions of children and adolescents living in a village in Dominica Found that children living without their biological father experienced significantly more days of illness and had significantly higher cortisol levels than those living with both parents (even if their father was often absent from the home, e.g., for work or after rows). -children who were living in a single mother/ blended family/ distant relatives were ill more likely (in % days) than those who lived with nuclear family or mother with maternal kin

Question 36

what do organisms have a limit on?

Answer 36

a limited energy supply

Question 37

list what a reproductive bout takes energy away from

Answer 37

``` • Each reproductive bout takes energy away from: o Growing o Mate seeking o Caring for previous offspring o Future reproduction o Self-repair (maintenance) ```

Question 38

what is LHT ostensibly about?

Answer 38

LHT is ostensibly about variation across species

Question 39

who proposed two selection types and what were these?

Answer 39

MacArthur (1962; MacArthur & Wislon, 1967)- r and K selection * Two opposing ecological strategies, r and K * r= rate of population growth (under optimal conditions) * K= carrying capacity of the environment (how many individuals can the environment sustain)

Question 40

what strategies did MacArthur propose?

Answer 40

) essentially had optimal conditions and the population was growing as fast as it could 2) constrained ecological conditions and when constrained the population can not grow in number meaning that the most successful individuals are the ones who produce the highest quality offspring who are going to be able to best compete for resources.

Question 41

when should r selection be used?

Answer 41

Under R selection the most successful individuals are those that produce the most offspring as fast as they can.

Question 42

when should K selection be used?

Answer 42

Under K selection it is those who invest their resources in high quality competitive offspring.

Question 43

what do r selected species tend to have as features?

Answer 43

``` R selected species tend to • Spend a short time growing • Reproduce early • Reproduce with multiple offspring per bout • Die young • Offspring likely to die of predation ```

Question 44

what do K selected species tend to have as features?

Answer 44

K selected species tend to • Spend a long time growing • Less reproductive bouts with small amounts of offspring • Spend long time rearing offspring before next bout of offspring • Live long

Question 45

are humans r or K and why?

Answer 45

• Humans are overwhelmingly K-selected- one of a small number of species that are at the end of the continuum (with e.g. elephants and whales) o Small family size (c. 5 children per female) o Long gestation o Long lactation and pre-reproductive period o Late reproduction o Long lifespan o Large brains

Question 46

but what has been argued about humans on the r or K continuum? and why?

Answer 46

been argued that some are more K than others (more at the extreme end of the human extreme) – We vary in family size (0-67 children/female highest documented to one female)‏ – We vary in lactation (0-c.48 months)‏ some don’t breast feed at all. – We vary in pre-reproductive period (8-18 years)‏ – We vary in timing of reproduction (12-45 years)‏ – We vary in lifespan factors (smoking, diet, risky behaviours etc)‏

Question 47

what does life history theory focus on rather than the genetic variation in individuals

Answer 47

Facultative variation

Question 48

how can genes cause alternative morphs?

Answer 48

* Due to fluctuating selection pressures- selection pressures changing back and fourth a lot some genomes favoured some years and some other years thus both remain in the population. * Frequency dependant selection- two morphs can co-exist in relative frequencies that balance out * Alternative adaptive strategies- can both exist in the population as occupy different social niches * (or lots of other reasons)

Question 49

what does facultative variation suggest

Answer 49

that there is plasticity to the brain and that this plasticity results in different conditional strategies • Differences in the environment produce differences in behaviour out of the same genotype

Question 50

why would we potentially have facultative variation. who proposed two ideas?

Answer 50

Nettle Bateson (2015)- came up with a model arguing two ways that this plasticity can work… 1) informational 2) somatic state based

Question 51

what is the informational (standard psychosocial acceleration models) about?

Answer 51

a informational model when you are early in lifespan you can extract information from your environment. Detecting something in childhood environment that predicts something about what environment will be in adulthood. Then develop into an adult have a phenotype that is appropriately developed for the predicted environment.

Question 52

what is an issue with the informational model?

Answer 52

- in order for this to work is medium turn environmental change- if environment is constant then childhood environment is fantastic predictor of adult environment but don’t need conditional adaptation because the information in the environment is always going to be the same so no benefit to evolving conditional adaptation. Alternatively, if environmental change is very rapid and is changing lots within a life span. Means that info in childhood doesn’t actually bear resemblance to environment in adulthood- thus conditional adaptation isn’t any good- not helping you to develop right phenotype In order for conditional, information adaptations to emerge what you need is an environmental change that is happening but that is slow enough that in a lifespan of an individual you are not likely to experience huge change

Question 53

what is the somatic state based (internal prediction models)

Answer 53

juvenile environmental input is effecting you- not using it as info but has a direct effect on you- e.g. if environment is very detrimental it is essentially damaging long term somatic (physical body) condition. You develop and whatever damage you took in youth persists and when you become an adult you develop a behavioural phenotype that is appropriate to you given the physical state you are in post-childhood. Adult phenotype is all about responding to the damage or advantage you’re carrying from early environment. Early environment is effecting the outcome but doing this directly through you not through any information about predicted adult environment- thus a little more predictive power as not restricted to which situations it is applicable in.

Question 54

what is less commonly considered compared to menarche

Answer 54

* Adrenarce- adrenal glands maturing- slowly from about age 6 * Thelarche- breast bud development * Spermarche: first ejaculation * All of these are hard to measure and require repeated questionaires or hormone measures

Question 55

earlier menarche in father absence ALSPAC cohort but issues

Answer 55

Culpin et al. (2014) • looked at ALSPAC cohort • found that father absence in early childhood was predicting maternal depression and financial issues in mid childhood • all of these, either directly or indirectly were all resulting in earlier menarche in females • multiple direct influences.. fits into idea that what we’re looking at is holistic stress issue though… meta-analyses if inputs you put in are rubbish then outputs out will be rubbish- Sohn (2017) argued that research is biased as less likely to get engagement from low SES participants. The ALSPAC cohort has tended to lose more of their low SES families certainly in the longitudinal studies. When this happens because being low SES is a form of stress we are losing a group of people who are really important in understanding this phenomenon. Conditioning on a collider—your meta analytic soup is only as good as your ingredient studies – Boothroyd

Question 56

best father absence and earlier onset puberty study and why

Answer 56

Ellis et al, 2003  Prospective, longitudinal, SES-controlled studies in two cohorts…!  Found that those who had been father absent in childhood were more likely to be sexually active in early- mid teens. In both US and NZ cohorts

Question 57

what have some argued in terms of puberty and LHT and becoming an adult

Answer 57

 Ellis (2004; Tither & Ellis, 2008) All well and good that evidence shows that father absence seems to be associated with 6 months or so earlier for menarche but why are we so convinced that this is all about reproducing- what about if instead this is not about becoming a reproductive adult but instead ending childhood. – Is early menarche a means of ending childhood rather than commencing adulthood…? o Argued always better to adapt strategy on the fly if you can because then can more readily adapt to changes in environment which is always going to be advantageous if possible. – If you’re in a bad ecology the last thing you want to be is be vulnerable so is much better to finish childhood, finish growing and become an adult so more protected against problems in environment

Question 58

what supports the idea that puberty is about ending childhood not starting adulthood

Answer 58

premature infants- they are very vulnerable, they engage in a period of catch up growth (initially plotted correct to gestational age for weight and length) but then plot them as normal age as they catch up. They are much more likely to reach puberty early and be short because stopped growing than infants born at term. o Premature babies are particularly vulnerable so shove energy early on into growing and then stop and get on with being an adult.

Question 59

impacts of father absence in preindustrial societies for health

Answer 59

The impacts of father absence on mortality in preindustrial populations, however, are rather more ambiguous. While there are notable examples of father absence or death of father being associated with slightly higher offspring mortality in both anthropological and historical records, Sear and Coall (2011) found that in more than half of small-scale societies for which data were published, father loss (by death or absence) had no significant link with offspring survival.

Question 60

facial evidence for health in nuclear families

Answer 60

Boothroyd and Perrett (2006) o Students at St. Andrews uni o Parents separated pre puberty, parents had bad relationship, parents had good relationship o People whose parents separated/ bad relationship looked less healthy than those whose parents were together and had a good relationship.

Question 61

evidence for childhood adversity causing huge implications

Answer 61

With implications for health… Nettle (2014) very representative of the population If look at c-reactive protein (inflammatory response marker shows strain immune system is under) if take adults and code on indicators of childhood adversity as adults they have the greatest levels of CRP. This is a long term cost as they are exerting energy on maintaining a high alert state of immunity and not on other things Also if look at self-rated health those who had childhood adversity were dramatically more unhealthy in 20s and those who had less childhood adversity maintained better health into later life. Its not that people who experience childhood adversity have a fast life-history theory that sucks away energy (although it does do this). Childhood adversity effect on self rated health- is small but significant. BUT if you then add in age of first pregnancy (stressful childhood, early pregnancy- which just took it out of you) what we find is that childhood adversity does predict age of 1st pregnancy this does have an effect on health but not losing much variance by adding pregnancy. So looks like its not about life history its about other things carrying that stress with you.

Question 62

is it all r/K? ticklist of what we would expect versus found

Answer 62

``` Is is all r/K  Do those with childhood stress/ father absence show  Early puberty- yes  Early reproduction – yes  Larger completed family size – no  Less parental investment- maybe ```

Question 63

what are caveats to the findings of LHT

Answer 63

o Much research doesn’t hold true for non-western populations o All the research is correlational- elaborate regression models even are still correlational it is not experimental o Is difficult to rule out the effect that genetic mediation has to play

Question 64

study on genetic influence on menarche

Answer 64

Rowe (2002) o Twins study (Mz; 0.57, Dz:0.32 concordance rates) o Genetic effects = 0.5, unshared environments= 0.43, shared environment= 0.07 o 7% of variance can be explained by factors that both twins share o Really father absence/ presence has to be shared environment – can’t argue that one twin is witnessing more family stress o This only explains a tiny effect of the overall variance

Question 65

what is an issue with Rowe's study?

Answer 65

To what extent is father absence itself associated with genes that may also predict age of menarche and if these two things are part of a genetic cluster that make you more r you might be more likely to be father absent as a male and hit puberty as a female

Question 66

study that tried to control for issues with Rowe's study

Answer 66

Tither & Ellis (2008) tried to control for this effect o Older vs younger siblings o 93 pairs from biologically intact families o 68 pairs from biologically disrupted families o Usually when older sister is closer to menarche so effect of parents cant effect of age of menarche. o Younger sisters in disrupted families are reaching puberty on average about 3 months before the older sisters. As younger sisters experiencing the stress younger in life

Question 67

what can be said overall about genetics

Answer 67

This does fit with the model that it is environment and not genetics- but 3 months difference is this a hugely vast amount of time would this make actual difference on people reproducing?

Question 68

what experimental evidence is there for LHT

Answer 68

non-human research on plasticity

Question 69

non-human research on telomeres

Answer 69

Nettle et al (2014) o Induced adversity shortens teleomeres (bits at end of chromosomes that get worn away when chromosomes are being copied when no telomeres left then damage to genetic code- one theory of aging) o Teleomeres in Starlings cross-fostered into different nests to be heavier (ADV) or smaller (DIS) than brood-males o At 12 days old can measure telomere length o Find that those at advantaged environment had sig longer telomeres at day 12 than those at the disadvantaged environment o Experimentally induced stress seems to be associated with shortening the telomeres faster.

Question 70

non-human experimental research on behavioral outcomes for LHT

Answer 70

Bateson et al., 2014- behavioural outcomes o Take a group of chicks from one nest o Some go into low competition environment some into high competition environment o Then behavioural test looking at how long they are willing to wait for a reward o Either the trial starts if you press a button straight away get one pellet but if wait for x number of seconds you might get 5 pellets- the question is how long do you have to make chicks wait for 5 pellets before they stop and just go for the one pellet o The more willing to wait for better reward- delay discounting- understanding that what you get at the end of it is worth the time taken. o What modulates willingness to wait for rewards- measure of impulsivity o Body condition (weight) and telomere condition is predicting impulsivity- those who have gained less weight because of competition have shorter telomeres and are more impulsive o Argues that the physical effects of being in the more difficult environment are directing learning to more impulsive behaviour.

Question 71

how does the behavioral research about telomeres relate to human findings?

Answer 71

Jergensen et al (2014) o Cortisol inhibits telomere repair in humans Thus elevated cortisol means that you take genetic damage at an earlier point- in that sense telomeres are an interesting candidate mechanism for stress impact on later development. The more telomere damage you are taking, the more long term genetic damage you will acquire, the shorter predicted life-span and the quicker you need to start producing. So does fit with somatic approach

Question 72

studies in west that father absence linked to +offspring and quicker

Answer 72

• More pregnancies o Berezckei & Csanaky (1996) but see miscarriage rates as this balanced it out • But certainly associated with more teenaged pregnancies & earlier first birth • Ellis et al (2003); Boothroyd et al (2013)

Question 73

how does the ecology of first birth differ in non-western samples for females

Answer 73

Father absence due to divorce delays Ache women’s age at first birth (Waynforth 2002. Handbook of Father Involvement). Those who are father present more likely to have had child in teens- within earliest period of potential reproduction In Ache father’s v important for daughter nutritional status- if don’t have dad about then will have lower fat %, bone density, muscle mass- not going to be ready to reproduce at earliest stage so father’s are important

Question 74

how does the ecology of first birth differ in non-western samples for males

Answer 74

Waynforth, Hurtado and Hill, 1998 Father absence due to divorce also delays Mayan men’s age at first birth. Years of father presence negatively predicts first birth Father’s v important in brokering children’s marriage so no father less likely to have a match and thus less likely to have children

Question 75

what did Sear and Coall find about non-WEIRD and WEIRD samples in their systematic review?

Answer 75

o In WEIRD – most of the time father absence accelerates age of first birth o In non-WEIRD- if include all significant studies then no effect- in all studies pretty even split between accelerate and delays o Non-WEIRD- although very varied collectively are a bit more representative of early human environments.

Question 76

what could indicate that nutrition has a role on menarche?

Answer 76

Ellison (1990) Is important as have to consider energetic ratios on mortality e.g. populations who live in mountains as may have huge calorie intake but also need to expend a huge amount to live in mountains Athletes are a good example of this – very healthy very high calorie intake o Physical stress and female reproduction o Minimum body fat required for menarche- women need more body fat than do men because need minimum fat to keep reproductive process o Female athletes often have disrupted menarcheal function- because of low body fat even considering their calorie intake. o Nutrition and nutritional stress is really important in human reproduction

Question 77

evidence that puberty onset is very different in WEIRD than Non-WEIRD samples

Answer 77

Sear et al. (pre-print)- Cross-cultural evidence does not support universal acceleration of puberty in father-absent households.

Question 78

what did Sear et al., pre-print find about girls?

Answer 78

WEIRD girls- 60% of studies show that father absence accelerates age of first birth and rest it is doing nothing NON-WEIRD girls- 72% of time doing nothing and then remaining time it is split between accelerating and delaying What is going on in the west does not bear any resemblance to what is going on in non-WEIRD countries

Question 79

what did Sear et al., pre-print find about boys?

Answer 79

WEIRD- boys (only 7 studies)- 55% time it does nothing, rest is maybe accelerating maybe delay Non-WEIRD boys (only 5 studies)- 2 studies no effect- 2 studies delay and 1 study showing acceleration Hard to say what is going on with boys as so much less well studies

Question 80

what can Sear et al.,'s pre print study tell us overall?

Answer 80

In terms of girls is very clear again that WEIRD samples are weird and we are seeing effects that we can not see with anything like the same simple clarity as when we try and look at non-weird samples where it seems that probably nothing going on but if there is can go either way.

Question 81

what is different in the west?

Answer 81

o Good nutritional status o Cultural tradition of biparental care- pretty typical of most humans most of the time in early years, but a pair bond that last from when a child is born to when they are reproducing themselves we can’t rely on as being a strong feature of human ancestory o Cultural tradition that our entire society is set up around pair-bonds (especially middle class) so that we don’t have the same family networks and family resources as are seen in small scale societies. Couples splitting in west huge financial issue whereas if think about dominican data kids living with mother and mothers kin are just as healthy as those living with nuclear families as in environment this is a completely normal way to live. o Potential phyco-social impact of parents splitting in our culture is potentially far greater than in other cultures.