Dr Sarah Johns
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.
Dr Sarah Johns is committed to understanding human reproductive timing and evolved sexual behaviour. During her most recent research period, she has amassed a large, detailed dataset – one of the most comprehensive of its kind from the UK. Sarah’s research was the first to study adolescent pregnancy from an evolutionary perspective and is yielding new and potentially groundbreaking results. She is in the process of preparing much of this material for publication and exploiting further the untapped potential in the dataset. Her work has policy implications, specifically for governmental teenage pregnancy strategy (in collaboration with Thomas Dickins). She has also conducted research exploring female genital colouration and male mating preferences, relationships between smoking, risk behaviour and mating success (funded by Novartis UK), and primate long bone trauma.
Dr Johns is programme convenor for the MSc in Evolution and Human Behaviour, 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
Francesca Whitehouse. The 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://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: https://peerj.com/articles/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. 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. (2017). Reply to Hagen and Thornhill. Evolution, Medicine, & Public Health [Online] 2017:24-26. Available at: https://doi.org/10.1093/emph/eow033.
Mahoney, P. et al. (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.
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
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.
Chapman, C., Legge, S. and Johns, S. (2007). Canopy height utilisation and trauma in three species of cercopithecoid monkeys Robson Brown, K. A. and Roberts, A. M. eds. BABAO 2004 Proceedings of the 6th Annual Conference of the British Association for Biological Anthropology and Osteoarchaeology BAR In: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
Johns, S. (2004). Subjective life expectancy predicts offspring sex in a contemporary British population. Proceedings- Royal Society of London B [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.
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.
Conference or workshop item
Myers, S. et al. (2016). Postnatal depression - Weighing the evolutionary evidence. in: 18th Annual Conference of the British Association for Biological Anthropology and Osteoarchaeology (BABAO).
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.
Miszkiewicz, J. et al. (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. et al. (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.
Myers, S. et al. (2016). Postnatal depression - Weighing the evolutionary evidence. in: European Human Behaviour and Evolution Association (EHBEA) Conference.
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.
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).
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. (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/.
Ellen, R.F., Lycett, S.J. and Johns, S.E. eds. (2013). Understanding cultural transmission in anthropology: a critical synthesis. 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.
Deter, C. et al. (2017). Chapter 6. Aspects of human osteology. in: Parker-Pearson, M., Richards, M. and Chamberlain, A. eds. The Beaker People: isotopes, mobility and diet in prehistoric Britain. Oxford: Oxbow. Available at: https://www.oxbowbooks.com/oxbow/the-beaker-people.html.