Portrait of Dr Sarah Johns

Dr Sarah Johns

Senior Lecturer in Evolutionary Anthropology
Academic Head Biological Anthropology
Programme Convenor for MSc Biological Anthropology


Dr Sarah Johns received her doctorate from the University of Bristol after completing an MPhil in biological anthropology at Corpus Christi College, Cambridge and an undergraduate degree in anthropology at the University of Pennsylvania. Sarah is a broadly trained anthropologist with research experience in palaeoarchaeology, human reproductive behaviour and the evolutionary psychology of human reproductive decision-making. Her primary research interest is in the variation of the age at first birth in humans, specifically focusing on teenage mothers, and how public health policy and evolutionary theory can be integrated.

Her PhD research, which was funded in part by the Gloucestershire Health Authority and the Department of Health, was an empirical investigation into whether teenage motherhood is the result of an evolved reproductive strategy that allows for variation in life-history event timings, as predicted by evolutionary anthropological theory. Specifically, Sarah tested the hypothesis that having children at an earlier age may promote lineage survival when the environment is unstable and risky and personal future is uncertain. In addition, she investigated a possible psychological mechanism linking environment and behaviour in this context. She believes research that links both function and mechanism is the future direction for evolutionary studies of human behaviour, and her research is pushing the boundaries of the field in this direction.

In 2008 Sarah was a joint recipient (with S. Legge and N. Newton-Fisher) of a teaching prize from the University of Kent for her role in developing the BSc in Anthropology and BSc in Biological Anthropology programmes.

Research interests

Dr Sarah Johns has broad research interests in reproductive and sexual health, and how evolutionary theory is a useful explanatory framework in this area. She also has expertise in evolutionary approaches to postnatal mental health and postnatal depression. Further details about this award-wining research project can be viewed here

Additionally, Dr Johns is an expert in teenage motherhood in the UK and she has carried out some of the first research to explain adolescent pregnancy as an adaptive strategy. Her work has significant policy implications, specifically for governmental teenage pregnancy and maternal mental health strategies. She has also led research exploring the sending of unsolicited sexual images, female genital colouration and male mating preferences, relationships between smoking, risk behaviour and mating success (funded by Novartis UK), weaning in medieval Britain, and primate long-bone trauma. 


Dr Johns is programme convenor for the MSc in Biological Anthropology, a programme with two routes, one of which is run jointly with the School of Psychology.


  • SE302: Foundations of Biological Anthropology
  • SE307: Thinkers and Theories
  • SE308: Skills for Anthropology and Conservation
  • SE533: Project in Anthropological Science (module convenor)
  • SE565: Sex, Evolution, and Human Nature (module convenor)
  • SE567: Quantitative Research Methods
  • SE570: Current Issues in Evolutionary Anthropology


  • SE855: Research Project (Evolution & Human Behaviour) (module convenor)
  • SE992: Advanced Topics in Evolutionary Anthropology
  • SE994: Advanced Topics in Human Behaviour (module convenor)


Current students

  • Hella Péter: The effects of water shortage on female chimpanzee social behaviour in the Budongo forest


  • Francesca WhitehouseThe menstrual cycle and female-to-female interactions: Explored through olfactory, visual and verbal/auditory communication. MSc by research. (Completed 2010)


  • Committee member, Biosocial Society: An international academic society that explores human biological and social diversity (from 2010).
  • Committee member, European Human Behaviour and Evolution Association (EHBEA): An interdisciplinary society that supports the activities of European researchers with an interest in evolutionary accounts of human cognition, behaviour and society (2005-2010).
  • Steering committee member, University of Kent Darwin 200 Committee (2008-2009).
  • Member (peer nominated), Centre for Sociology, Anthropology and Politics (C-SAP): Anthropology reference group responsible for developing the teaching of anthropology in UK higher education (2003-2010).
  • Conference sessions organised: Charity, Philanthropy, and Volunteerism, ESRC-funded Darwin’s Medicine Seminar series, University of Kent (2009); Human Ecology, The British Association for Biological Anthropology and Osteoarchaeology, University of Bristol (2004).
  • Conference session chair: European Human Behaviour and Evolution Association annual meeting (2009); British Society for Population Studies Annual Meeting (2005); Human Behavior and Evolution Society Annual Meeting (2004).



  • Myers, S. and Johns, S. (2019). Male infants and birth complications are associated with increased incidence of postnatal depression. Social Science & Medicine [Online] 220:56-64. Available at: https://dx.doi.org/10.1016/j.socscimed.2018.10.008.
    Rationale: A growing body of literature links both depressive symptoms generally, and those specifically in the postnatal period, with an inflammatory immune response. Evolutionary medical approaches, such as the Pathogen Host Defence Theory of Depression (PATHOS-D), have likened depression to sickness behaviour in other mammals, and propose that the characteristics associated with depression are protective when an individual is experiencing pathogenic threat. Many known risk factors for depressive symptoms are associated with activation of inflammatory pathways, opening up the potential for identifying novel risk factors based on their inflammation causing effects.

    Objective: Both the gestation of male foetuses and the experience of birth complications have documented associations with increased inflammation, yet their relationships with postnatal depression (PND) are currently unclear.

    Method: Here we use the complete reproductive histories of 296 women from contemporary, low fertility populations gathered by retrospective survey to assess whether the odds of PND increased when mothers gave birth to male infants or experienced birth complications, using generalised estimating equation models controlling for individual effects of the mother and other known PND risk factors.

    Results: We found the odds of PND increased by 71–79% when male infants were born compared to female infants. The occurrence of birth complications increased the odds of PND by 174% compared to having no complications. Testing for interaction effects found that, while always at increased risk of PND, women with a tendency towards symptoms of depression, anxiety, and stress at other points in the life course had reduced odds of PND when experiencing birth complications, suggesting such women may elicit greater support.

    Conclusions: These results highlight two novel PND risk factors, male infants and birth complications, which can be easily assessed by health professionals.
  • Myers, S. and Johns, S. (2018). Postnatal depression is associated with detrimental life-long and multi-generational impacts on relationship quality. PeerJ [Online] 6:e4305. Available at: http://dx.doi.org/10.7717/peerj.4305.
    Postnatal depression (PND) is known to be associated with a range of detrimental child and adolescent outcomes, resulting from its disruptive impact on mother-child relationship quality. However, until now little has been known about the impact of PND on the longer-term relationships between mothers and their children, and any intergenerational effects this may have. Mother-child relationship quality is of interest from an evolutionary perspective as it plays a role in the accrual of offspring embodied capital, thus affecting offspring quality and offspring’s capacity to subsequently invest in their own children. Relationships with offspring also mediate grandparent-grandchild relations; if PND negatively affects long-term mother–offspring relationship quality, it is also likely to negatively affect grandmaternal investment via reduced grandmother–grandchild relationship quality. Here, we use responses to a retrospective questionnaire study of postmenopausal women, largely from the UK and US, to assess the impact of PND occurring in generation 1 on mother–child relationship quality across the life course of the child (generation 2) with whom it was associated, and also on the relationship quality with grandchildren (generation 3) from that child. Average mother-child relationship quality was lower when the child’s birth was associated with PND. Multi-level regression modelling found that mother-child relationship quality decreased as PND symptom severity increased after controlling for individual effects and a variety of other factors known to influence relationship quality (individual mothers n = 296, mother-child dyads n = 646). Additionally, intergenerational relationships appear to be affected, with PND negatively associated with grandmother-grandchild relations (individual grandmothers n = 125, relations with grandchildren from n = 197 grandmother-parent dyads). That PND has long-term detrimental consequences for mother-child relationships, well beyond adolescence, highlights the need for investment in strategies to prevent PND and its cascade of negative multigenerational effects.
  • Myers, S., Burger, O. and Johns, S. (2017). Reply to Hagen and Thornhill. Evolution, Medicine, & Public Health [Online] 2017:24-26. Available at: https://doi.org/10.1093/emph/eow033.
  • Myers, S. and Johns, S. (2017). Male infants, risk, and postnatal depression: Evidence supporting the Trivers-Willard hypothesis in a contemporary low-fertility context. Unpublished.
  • Myers, S., Burger, O. and Johns, S. (2016). Postnatal depression and reproductive success in modern, low-fertility contexts. Evolution, Medicine, and Public Health [Online] 1:71-84. Available at: http://dx.doi.org/10.1093/emph/eow003.
    Background and objectives: Postnatal depression (PND) presents a puzzling phenomenon to evolutionary
    anthropologists as it is highly prevalent and yet detrimental to child development and maternal
    health. Adaptive explanations have been proposed, but have not been tested with data that directly link
    PND to female fertility.

    Methodology: A survey was designed to gather complete reproductive histories and retrospective measures
    of PND to measure the effects of PND on fitness. Respondents were born between 1930 and 1967,
    with the majority based in the UK during their childrearing years. The hypothesis that PND is detrimental
    to fitness is assessed using Mann–Whitney U tests on completed fertility. Binary logistic regression
    modelling is used to test the hypothesis that PND reduces the likelihood of parity progression.

    Results: Women experiencing PND at their first or second birth have lower completed fertility, with PND
    at the first birth leading to lowered fertility. Logistic regression analyses show that this is the result of
    reductions in the likelihood of parity progression to a third birth when PND is experienced at the first
    birth or when repeat bouts occur.

    Conclusions and implications: Our results call into question adaptationist arguments, contribute to the
    growing understanding of the importance of emotional wellbeing to fertility decision making, and given
    the economic consequences of markedly below replacement fertility, highlight a potential new source of
    financial incentive to invest in screening and preventative measures to ensure good maternal mental
  • Mahoney, P., Schmidt, C., Deter, C., Remy, A., Slavin, P., Johns, S., Miszkiewicz, J. and Nystrom, P. (2016). Deciduous enamel 3D microwear texture analysis as an indicator of childhood diet in medieval Canterbury, England. Journal of Archaeological Science [Online] 66:128-136. Available at: http://dx.doi.org/10.1016/j.jas.2016.01.007.
    This study conducted the first three dimensional microwear texture analysis of human deciduous teeth to reconstruct the physical properties of medieval childhood diet (age 1-8yrs) at St Gregory's Priory and Cemetery (11th to 16th century AD) in Canterbury, England. Occlusal texture complexity surfaces of maxillary molars from juvenile skeletons (n=44) were examined to assess dietary hardness. Anisotropy values were calculated to reconstruct dietary toughness, as well as jaw movements during chewing. Evidence of weaning was sought, and variation in the physical properties of food was assessed against age and socio-economic status. Results indicate that weaning had already commenced in the youngest children. Diet became tougher from four years of age, and harder from age six. Variation in microwear texture surfaces was related to historical textual evidence that refers to lifestyle developments for these age groups. Diet did not vary with socio-economic status, which differs to previously reported patterns for adults. We conclude, microwear texture analyses can provide a non-destructive tool for revealing subtle aspects of childhood diet in the past.
  • Dickins, T., Johns, S. and Chipman, A. (2012). Teenage Pregnancy in the United Kingdom: A Behavioral Ecological Perspective. Journal of Social, Evolutionary, and Cultural Psychology [Online] 6:344-359. Available at: http://shell.newpaltz.edu/jsec/articles/volume6/issue3/Dickins_Vol6Iss3.pdf.
    In this paper we describe teenage pregnancy and motherhood in the United Kingdom. This has been regarded as a key social policy issue for some time and is the focus of policy intervention under the current administration. We argue that policy has been based on simple models of teenage pregnancy that have failed to take into account the complex biological nature of reproductive behavior. Our claim is that the U.K. government would be well advised to take a life-history approach to this issue, and we outline what this means and what is currently known as a consequence of research in this area, concluding with lessons that should be drawn by those working in policy.
  • Johns, S., Hargrave, L. and Newton-Fisher, N. (2012). Red Is Not a Proxy Signal for Female Genitalia in Humans. PLoS ONE [Online] 7:e34669. Available at: http://dx.doi.org/10.1371/journal.pone.0034669.
    Red is a colour that induces physiological and psychological effects in humans, affecting competitive and sporting success, signalling and enhancing male social dominance. The colour is also associated with increased sexual attractiveness, such that women associated with red objects or contexts are regarded as more desirable. It has been proposed that human males have a biological predisposition towards the colour red such that it is ‘sexually salient’. This hypothesis argues that women use the colour red to announce impending ovulation and sexual proceptivity, with this functioning as a proxy signal for genital colour, and that men show increased attraction in consequence. In the first test of this hypothesis, we show that contrary to the hypothesis, heterosexual men did not prefer redder female genitalia and, by extension, that red is not a proxy signal for genital colour. We found a relative preference for pinker genital images with redder genitalia rated significantly less sexually attractive. This effect was independent of raters' prior sexual experience and variation in female genital morphology. Our results refute the hypothesis that men's attraction to red is linked to an implied relationship to genital colour and women's signalling of fertility and sexual proceptivity.
  • Johns, S. (2011). Perceived environmental risk as a predictor of teenage motherhood in a British population. Health and Place [Online] 17:122-131. Available at: http://dx.doi.org/10.1016/j.healthplace.2010.09.006.
    Previous studies have shown that strong relationships exist between deprived environments and teenage motherhood. However, such studies have predominantly identified deprivation using neighbourhood-wide measures of socio-economic status. Few studies of teenage parenthood have examined how individuals perceive their environment and the importance of this perception on reproductive behaviour and timing. Using data collected from a sample of women living the county of Gloucestershire, UK, this paper explores the predictive value of two methods of assessing the environment: (1) the structural component—deprivation at the neighbourhood level and (2) the individual’s subjective experience of her pre-pregnancy environment, when examining how the wider environmental context can influence the decision of becoming a teenage mother. The results indicate that a woman’s perception of her neighbourhood of residence at the time she conceived, her perceived environmental risk, may be a more discriminating predictor of teenage motherhood than deprivation measured by ward economic and deprivation indicators.
  • Johns, S., Dickins, T. and Clegg, H. (2011). Teenage pregnancy and motherhood: How might evolutionary theory inform policy?. Journal of Evolutionary Psychology [Online] 9:3-19. Available at: http://dx.doi.org/10.1556/JEP.9.2011.37.1.
    Teenage pregnancy and motherhood are considered to be pressing social concerns and, in the majority of developed countries, are often viewed as problems in need of solutions. While a number of factors are associated with teenage motherhood, the underlying causes remain elusive. Despite a lack of consensus, policy aimed at ‘solving’ teenage motherhood is typically based on these proposed proximate correlates; addressing these, rather than the cause. Recent appraisals of this approach suggest that it may not be working effectively, if at all, and policy makers might be in need of some novel approaches. This paper discusses how policy decisions concerning reproductive timing may benefit from the perspective provided by evolutionary life-history theory, and why policy ought to take into account the hypothesis that teenage motherhood is the outcome of an adaptive response of an evolved reproductive strategy to conditions of risk and uncertainty; that having children at an earlier age may promote lineage survival when personal future is uncertain.
  • Johns, S. (2004). Subjective life expectancy predicts offspring sex in a contemporary British population. Proceedings of the Royal Society B Biological Sciences [Online] 271:S474-S476. Available at: http://dx.doi.org/10.1098/rsbl.2004.0220.
    There is evidence that women who are in poor physical condition or who reside in deprived environments are more likely to give birth to daughters than to sons. Under deprived environmental conditions, or when in poor physical health, it has been hypothesized that parents should take into account the available resources and manipulate the sex of any children born. Using subjective life expectancy (SLE) as a measure of how an individual views their future health and environment, I demonstrate that there is an association between the sex of the first child and SLE in a sample of mothers from a contemporary British population (Gloucestershire, UK). SLE was a significant predictor of offspring sex: women who believed that they had longer to live were more likely to have had a male birth than women who thought they would die earlier. Detection of such a bias among the children of British mothers may provide evidence that the sex ratio under relatively affluent Western conditions can still be influenced by adverse environmental or poor maternal condition.
  • Lawlor, D., Shaw, M. and Johns, S. (2001). Teenage pregnancy is not a public health problem. British Medical Journal [Online] 323:1428-1428. Available at: http://dx.doi.org/10.1136/bmj.323.7326.1428.

Book section

  • Deter, C., Mahoney, P., Johns, S. and Thomas, S. (2019). Chapter 6. Aspects of human osteology and skeletal biology. In: Parker Pearson, M., Sheridan, A., Jay, M., Chamberlain, A., Richards, M. P. and Evans, J. eds. The Beaker People: Isotopes, Mobility and Diet in Prehistoric Britain. Oxford: Oxbow, pp. 253-291. Available at: https://www.oxbowbooks.com/oxbow/the-beaker-people.html.
    This chapter presents the results of three studies
    that were undertaken as part of the Beaker People
    Project (BPP), and which complemented the
    osteological work undertaken for the Beakers
    and Bodies Project as reported in Chapter 5. The
    first study examined the age and sex of 201
    individuals that had been deemed suitable for
    isotopic analysis of dental enamel. The second
    examined tooth enamel defects in 12 juvenile
    skeletons, as an indicator of non-specific infant
    stress. The third was a craniometric study of
    skulls from the Peak District, designed to assess
    the validity of previous claims for a change in
    skull shape from dolichocephalic (long-headed)
    during the Neolithic, to brachycephalic (roundheaded)
    from the Chalcolithic onwards, and to
    explore the possible reasons for the observed
    differences. The chapter ends by considering
    the results of the craniometric study in the
    light of isotopic evidence suggesting a high
    incidence of non-local individuals within the
    Peak District dataset.
  • Humle, T. and Newton-Fisher, N. (2013). Culture in Non-human Primates: Definitions and Evidence. In: Ellen, R. F., Lycett, S. J. and Johns, S. E. eds. Understanding Cultural Transmission in Anthropology: A Critical Synthesis. Berghahn Books.
    The attribution of culture to non-human animals has been controversial and continues to fuel much heated debate, much of which hinges on how culture is defined. We illustrate how definitions have become less human-centric as observations from wild primates have led to a new discipline – cultural primatology – and challenged the idea of culture as uniquely human. Although cultural primatology has it roots in field studies of wild primates, the weight of captive studies across a variety of species has resulted in a comparative view of culture which emphasises the mechanism of transmission. We argue that, while this has broadened the species and behaviours that have been considered ‘cultural’, it weakens the usefulness of comparative studies in understanding the evolutionary origins of human culture. We prefer a definition that centres on the concept of culture as an array of behaviour patterns across multiple domains that vary between groups or populations due to differing histories of social transmission. We argue for the necessity of field studies of wild primates in the comparative study of culture, providing examples of how such studies allow both the identification of cultures across non-human primate social groups and the mechanisms by which behaviours are transmitted both within and between groups. Such studies are essential for an ecologically valid understanding of culture, and to investigate how social dynamics, ecology and demographics shape culture and the diffusion and dissemination of socially learned behaviours.
  • Puri, R. (2013). Transmitting Penan basketry knowledge and practice. In: Ellen, R. F., Lycett, S. J. and Johns, S. E. eds. Understanding Cultural Transmission in Anthropology. Oxford: Berghahn Books, pp. 266-299. Available at: http://www.berghahnbooks.com/title.php?rowtag=EllenUnderstanding.
    This chapter describes Penan (Indonesian Borneo) basket making and the way it is simultaneously adapting to new circumstances while still maintaining continuity with past traditions. The explanation for this continuity resides in the complex intersections of processes of cultural transmission and the sociocultural and economic contexts in which they occur. Of particular importance is the way in which Penan egalitarianism opens up the possibilities for simultaneous transmission and transformation of basketry practices between and within the generations.
  • Ellen, R. and Fischer, M. (2013). Introduction: on the concept of cultural transmission. In: Ellen, R. F., Lycett, S. J. and Johns, S. E. eds. Understanding Cultural Transmission in Anthropology: A Critical Synthesis. New York, Oxford: Berghahn, pp. 1-54.
  • Johns, S. and Belsky, J. (2007). Life transitions: becoming a parent. In: Salmon, C. A. and Shackleford, T. K. eds. Family Relationships: An Evolutionary Perspective. Oxford: Oxford University Press, pp. 71-90. Available at: http://dx.doi.org/10.1093/acprof:oso/9780195320510.003.0004.
    The birth of a child is a commonplace event, yet for the two individuals who become parents this transition to parenthood is a major life event. For men and women the challenges of parenthood will differ, and their relationship will undergo change as the demands of their new roles become apparent. Parenthood has the potential to change both men's and women's feelings about themselves and their relationship. This chapter explores the transition to parenthood, in particular asking why this can be difficult, why the experience of having a child is different for men and women, how the timing of the transition can be influenced by family relationships, and how the ease of transition for one generation can influence the timing of the transition in subsequent generations. This includes both proximate psychological aspects of becoming a parent and evolutionary or ultimate explanations of human reproductive patterns and parenting behaviors.
  • Chapman, C., Legge, S. and Johns, S. (2007). Canopy height utilisation and trauma in three species of cercopithecoid monkeys. In: Robson Brown, K. and Roberts, A. eds. BABAO 2004: Proceedings of the 6th Annual Conference of the British Association for Biological Anthropology and Osteoarchaeology. Oxford, UK: British Archaeological Reports Publishing, pp. 15-18.
    Trauma was studied in the long bones (femur, tibia, fibula, humerus, radius, and ulna) of primate skeletal remains based at the Powell-Cotton Museum, Birchington, Kent, UK. The specimens were from three different arboreal quadrupeds who are known to travel at overlapping but differential levels in the the tree canopy; Cercopithecus cephus, and Piliocolobus badtus. Of the 80 skeletons examined, 15 had evidence of healed fractures. The femur was found to be the most frequent type of bone broken amongst all three species, followed by the humerus, then radius. Although there was a trend toward a higher trauma frequency based on increased canopy travelling height, the differences were nott statistically different

Conference or workshop item

  • Myers, S. and Johns, S. (2018). A life history perspective on maternal emotional investments during infancy. In: 13th Conference of the European Human Behaviour and Evolution Association (EHBEA). p. 42. Available at: http://psychology.pte.hu/ehbea2018.
    Objective Life history approaches to parental investment have typically highlighted trade-offs humans
    make by measuring variations in the transfer of resources such as knowledge, wealth, or social status.
    Such transfers often occur later in the life of offspring, yet parents make investments in their offspring
    from conception. Mother-infant emotional bonding is associated with infant development, thus may
    reflect an early form of maternal investment. Bonding may also guide long-term investment
    motivations, thus have both direct and indirect effects on offspring quality. We use two measures of
    bonding to assess whether access to emotional support from allocarers affects maternal emotional
    investment trade-offs, and measures of a mother’s available emotional resources to assess whether
    emotional investment is costly.
    Methods A longitudinal survey study tracked 67 Western women from pregnancy to 6 months
    postpartum. Multiple regression models assessed whether: 1) emotional support positively predicts
    maternal investment; 2) maternal investment positively predicts a decline in maternal emotional
    resources. Moderation analysis assessed whether 3) emotional support acts as a buffer against declines
    in emotional resources.
    Results Level of overall emotional support from allocarers positively predicted bonding strength, as did
    support from own family and friends. However, support from the infant’s father negatively predicted
    bonding strength and time taken to bond, while support from the father’s family negatively predicted
    the time taken to bond. Bonding strength positively predicted falls in overall emotional resources and
    emotional intelligence; level of overall support received moderated a variety of dimensions of this
    Conclusions Maternal emotional investments appear contingent on circumstance, with bonding
    incurring a cost when access to emotional support from allocarers is low. Mothers make higher
    emotional investments in association with higher support from friends and kin, but may offset costs
    when support is available from their infant’s paternal kin.
  • Myers, S., Burger, O., Stieglitz, J. and Johns, S. (2016). Postnatal depression - Weighing the evolutionary evidence. In: 18th Annual Conference of the British Association for Biological Anthropology and Osteoarchaeology (BABAO).
  • Miszkiewicz, J., Bennett, C., Johns, S. and Mahoney, P. (2016). Femoral bone remodeling comparisons between adult males and females from medieval England. In: The 85th Annual Meeting of the American Association of Physical Anthropologists.
    Differences in bone metabolism between males and females in extant populations provide a basis from which to reconstruct gender divisions in labor for ancient humans. However, little is currently known about bone microstructure variation with sex in ancient English societies. Here, we access cortical bone remodeling using histological methods to compare males and females from the medieval period in Canterbury, England.

    Following standard anthropological guidelines, sex and age-at-death were estimated for a total of 445 human skeletons, yielding 49 young and 180 middle-aged males, and 77 young and 139 middle-aged females. Static histomorphometry parameters were recorded in thin sections removed from the posterior femoral midshaft. Osteon population and osteocyte lacunae densities were compared between the sexes within each age category using univariate statistics.

    Significantly higher remodeling was observed in males when compared to females. For example, osteon population density was higher in young (p = .044) and middle-aged (p. = .000) male groups when compared to females. Osteocyte lacunae were also denser (p = .001) in young males than females. Changes in cortical remodeling remained consistent when our analysis was adjusted for femoral robusticity to account for sexual dimorphism in bone size.

    Our findings agree with bone physiology principles, and are congruous with previous histological studies of other archaeological populations. We link higher remodeling in males to greater mechanical loads. Medieval lifestyle differences that include gender specific labor divisions are inferred. Results are discussed in a hormonal bone physiology framework, and bone mass attainment variation with age and sex.
  • Myers, S., Burger, O., Stieglitz, J. and Johns, S. (2016). Postnatal depression – an evolutionary overview. In: European Human Behaviour and Evolution Association (EHBEA) Conference.
    Postnatal depression (PND) presents a puzzling phenomenon to evolutionary anthropologists as it is highly prevalent and yet detrimental to child development and maternal health. Adaptationist explanations use parental investment theory to propose that it is an adaptive signal to a mother that she is experiencing a cost to her fitness by investing in a particular offspring and should therefore reduce/eliminate investment, while displays of distress elicit support from kin. Mismatch hypotheses on the other hand contend PND’s aetiology lies in ‘modern’ parenting styles and developed environments. A third line of explanation views PND as an immune response triggered by external stressors, tying it in with recent evolutionary explanations of depression more generally which see it as akin to sickness behaviour in mammals and thus a maintenance strategy in response to threat. Until now very little direct evidence has been brought to bear on the fitness consequences of PND which may enable the relative merits of these explanatory frameworks to be weighed. Here we present data on the effects of PND from two populations that vary in socio-economic setting; a Western sample and the Tsimane forager-horticulturalists from Bolivia. In the Western sample, furthering recently published work, we examine two fitness relevant measures – fertility and relationship quality – over two generations. In the Tsimane we examine the relationship between PND and fertility. Drawing comparisons we assess whether patterns documented in the Western sample are unique to Westernised contracepting populations, discuss the implications for the various evolutionary explanations, and suggest areas for future research.
  • Johns, S. and Myers, S. (2016). Male infants, risk, and postnatal depression: Evidence supporting the Trivers-Willard hypothesis in a contemporary low-fertility context. In: European Human Behaviour and Evolution Association (EHBEA) Conference. Available at: http://ehbea.com/conference2016/.
    Maternal care is obligate in mammals to ensure offspring survivability; however levels of investment are flexible dependent on resource availability. Parental investment theory predicts a mother should cease investing in an individual offspring when the benefits of the investment to her inclusive fitness are outweighed by the costs. The Trivers-Willard hypothesis predicts that a son of high quality will out-reproduce a daughter of comparable quality, while a daughter will have higher reproductive success than a son if both are of low quality. Postnatal depression is suggested by some evolutionary theorists to reflect active withdrawal of maternal investment in humans under conditions where continued investment is too costly. If this is the case then it should be expected to 1) conform to Trivers-Willard predictions and be both more common in association with sons than daughters, and 2) be more common in circumstances in which investment in sons is more costly. We test these hypotheses using data collected from a survey of women's complete reproductive histories which utilised retrospective measures of postnatal depression. Multilevel modelling showed that women were more likely to suffer postnatal depression after the births of sons than after the births of daughters, when controlling for other postnatal depression risk factors. Having sons was also found to elevate postnatal depression risk when mothers experienced low social support or complicated births. This is a novel and important finding of which healthcare professionals should be made aware.
  • Myers, S., Burger, O., Stieglitz, J. and Johns, S. (2016). Postnatal depression - Weighing the evolutionary evidence. In: European Human Behaviour and Evolution Association (EHBEA) Conference.
  • Myers, S., Burger, O. and Johns, S. (2015). Postnatal depression and reproductive success in modern, low-fertility contexts. In: Evolutionary Medicine Conference: Interdisciplinary Perspectives on Human Health and Disease. Ashdin Publishing. Available at: https://doi.org/10.4303/jem/235924.
  • Johns, S. and Whitehouse, F. (2014). Female intrasexual competition and the detection of cyclical fertility status. In: Human Evolution and Behaviour Network (HEBEN) Annual Conference. Available at: https://www.uantwerpen.be/en/rg/mios/news/conferences/past-conferences/2014/heben-2014/.
    Previous research has shown women become more competitive towards other women when they
    are most likely to conceive. However, the question of whether women can detect the fertility
    status their rivals and the consequences of being able to do so, has largely been ignored. Our
    results are the first to show that cyclical infertility is preferred by women judging the facial
    appearance of other women who were presented as “rivals”. Luteal phase images were
    significantly favored compared to those taken during either the follicular or menstrual phase,
    under scenarios where the presence of a fertile rival could threaten mate procurement or female
    social bonds. They support a hypothesis that an ability to detect fertility, and to be wary of it,
    may be part of an evolved strategy that modulates female/female agonistic interactions whereby
    women prevent their allies and potential sexual partners from having contact with ovulating
  • Johns, S., Hargrave, L. and Newton-Fisher, N. (2013). Red is not a proxy signal for human female genitalia. In: European Human Behaviour and Evolution Association Conference.
  • Johns, S., Hargrave, L. and Newton-Fisher, N. (2012). Red is not a proxy signal for human female genitalia. In: 81st Meeting of American Association of Physical Anthropologists.
  • Johns, S. (2009). Predicting the future: Teenage motherhood and time perspective. In: European Human Behaviour and Evolution Association. Available at: http://ehbea.com/old/conf/2009/files/EHBE2009_summary.pdf.
  • Johns, S. (2008). Teenage pregnancy and motherhood: How might evolutionary theory inform policy?. In: Trade-Offs in Female Life Histories: Raising New Questions in an Integrative Framework. IUSSP International Seminar.
  • Johns, S. (2005). Understanding why teenage motherhood occurs in deprived environments: An evolutionary approach. In: British Society for Population Studies Annual Meeting.
  • Chapman, T., Legge, S. and Johns, S. (2004). The higher they live the further they fall: Travelling height and trauma among five species of primate. In: British Association for Biological Anthropology and Osteoarchaeology (BABAO). Available at: http://www.babao.org.uk/conferences/annual-conference-2004/.
  • Johns, S. (2004). Subjective life expectancy and offspring sex: Support for the Trivers-Willard hypothesis. In: Annual Meeting of the Human Behavior and Evolution Society (HBES).
  • Johns, S. (2003). Teenage Motherhood: An evolved reproductive strategy under conditions of environmental risk. In: British Society for Population Studies.
  • Johns, S. (2003). Reproductive trajectory, environmental risk, and teenage motherhood. In: British Association for Biological Anthropology and Osteoarchaeology (BABAO). Available at: http://www.babao.org.uk/conferences/annual-conference-2003/.

Edited book

  • Ellen, R., Lycett, S. and Johns, S. (2013). Understanding Cultural Transmission in Anthropology: A Critical Synthesis. Vol. 26. Ellen, R. F., Lycett, S. J. and Johns, S. E. eds. New York, Oxford: Berghahn.

Research report (external)

  • Johns, S. (2001). Descriptive Statistics of Teenage Mothers and Older Mothers in Gloucestershire. An Official Report Compiled for the Gloucestershire Teenage Pregnancy Co-Ordinators. Gloucestershire Health Authority.


  • Myers, S. (2017). Maternal Investment and Postnatal Depression - An Evolutionary Approach.
    Postnatal depression is detrimental to maternal health and wellbeing, associated with poor developmental outcomes in children, and has prevalence estimates ranging from 13-60%; as such it is of significant public health concern and its origins are of interest from an evolutionary perspective. A growing movement within evolutionary research highlights the utility of evolutionary theory to elucidate the origins of health issues and indicate both novel approaches to treatment and prevention. A relatively longstanding, yet largely untested, existing evolutionary approach to postnatal depression proposes that it is a mechanism facilitating maternal investment decisions. More recently it has also been framed, somewhat complementarily, as the result of an evolutionary mismatch.

    Using the responses to a retrospective survey study which collected the complete reproductive histories of women and was uniquely designed to capture their experiences of postnatal depression, the first data chapter of this thesis explores whether there is support for adaptationist hypotheses that postnatal depression exhibits good design as a mechanism guiding maternal reproductive trade-offs. The results, combined with critiques put forward here and by other authors, suggest an alternative approach to postnatal depression is warranted.

    A limitation of both evolutionary and more traditional approaches to postnatal depression is that the commonly recognised risk factors for the condition fail to capture all the women who develop the condition. Recent developments in research into general depression, as opposed to postnatal depression, have highlighted the role of the immune system in symptom aetiology. This has led to a number of evolutionary researchers proposing that depression reflects an evolved inflammatory response to biological and social threat, with perceived social threat acting as an indicator of the likelihood of imminent biological threat. Inflammation then acts as the ultimate risk factor in the causal pathway to depression, and by extension postnatal depression, and suggests more attention needs to be paid to the social perceptions of women during pregnancy and early motherhood.

    Data chapters 3-6 explore the social pressures surrounding women about motherhood, the role such pressures play in generating feelings of shame (an emotional marker of social threat causally linked to general depression development), and the ability of shame to predict postnatal depression. Particular attention is paid to pressures surrounding socially approved levels of maternal investment, namely in the form of bonding. Bonding is of interest due to the documented association between postnatal depression and poor bonding as well as the pressures placed on women in contemporary, developed populations, highlighted by sociologists and feminist scholars, as a result of the emphasis on the importance bonding for child development. The role of social isolation, another form of social threat linked to general depression, in postnatal depression risk is also assessed. In so doing, a new model for maternal emotional investments is developed based on embodied capital theory and the results of two further data sets are presented - the first is a longitudinal survey study tracking women across the perinatal period assessing their experience of social pressure, shame, and postnatal depression, and the second an experimental priming study designed to assess if social threat can be primed using popular and social media relating to mothering. Results derived from these studies are supportive of the perception of social threat being a largely unrecognised risk factor in postnatal depression and the thesis concludes with a discussion of the public health implications which stem from this novel insight.


  • Ruhland, S. (2019). Ignorance or Intent? Motivations and Predictive Factors for the Sending of Unsolicited Sexual Images.
    A shift in mating behaviours caused by the inception of the internet has enabled new forms of sexual communication, in particular the exchange of graphic images. There is a fundamental lack of empirical research conducted on the origins of and motives for self- taken sexual images, both solicited and unsolicited. The incentives for the sending of such images are unknown, as well as the prevalence of the behaviour in general. Within the purposes of this research project I established the demographic context of sending nude images, identified people's main intentions and consequences, as well as the underlying psychological differences of those who send unrequested sexual images. In order to do so, I created a predictive model for the sending of unsolicited nude images, designed and validated a new scale for measuring attitudes towards sending nudes and provided evidence for gender-based differences when it comes to intentions and perceptions around the sending of self-taken sexual images. This research project provides evidence to suggest the sending of unsolicited graphic images is predicted by psychopathy, self-rated mate value and an accepting attitude towards sending nudes in men, whereas in women it is predicted by narcissism and a liberal attitude towards sending nudes. These gender differences have unique implications, both in terms of their potential to cause harm and regarding their perception by recipients, and should therefore be treated distinctly by governmental and educational institutions.
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