Biocultural perspectives on maternal mortality and obstetrical death from the past to the present

Maternal mortality in Eastern Democratic Republic of Congo: a 10-year multi-zonal institutional death review

BACKGROUND

Maternal mortality (MM) remains a real scourge that hits hardest in the poorest regions of the world, particularly those affected by conflict. However, despite this worrying reality, few studies have been conducted about MM ratio in the Democratic Republic of Congo (DRC). The study aimed to describe the trends as well as the epidemiological profile and causes of reported institutional maternal deaths between 2013 and 2022 in Eastern DRC.

METHODS

A retrospective descriptive study was conducted between March 2023 and August 2023 in eight Health Zones (HZ), five in South Kivu Province (Mwana, Minova, Miti-Murhesa, Kamituga and Idjwi) and three in North Kivu Province (Kirotshe, Karisimbi and Kayna) in the eastern region of the DRC. Our study covers 242 health facilities: 168 health centers (HC), 16 referral health centers (RHCs),50 referral hospitals (RH) and 8 general referral hospitals (GRHs). Data from registers and medical records of maternal deaths recorded in these zones from 2013-2022 were extracted along with information on the number of deliveries and live births. Sociodemographic, clinical parameters, blood and ultrasound tests and suspected causes of death between provinces were assessed.

RESULTS

In total, we obtained 177 files on deceased women. Of these, 143 (80.8%) were retained for the present study, including 75 in the 3 HZs of North Kivu and 68 in the 5 HZs of South Kivu. From 2013 to 2022, study sites experienced two significant drops in maternal mortality ratio (MMR) (in 2015 and 2018), and a spike in 2016-2017. Nonetheless, the combined MMR (across study sites) started and ended the 10-year study period at approximately the same level (53 and 57 deaths per 100,000 live births in 2013 and 2022 respectively). Overall, 62,6% of the deaths were reported from secondary hospital. Most deaths were of married women in their thirties (93.5%). Almost half (47.8%) had not completed four antenatal consultations. The main direct causes of death were, in decreasing order of frequency: post-partum haemorrhage (55.2%), uterine rupture (14.0), hypertensive disorders (8.4%), abortion (7.7%) puerperal infections (2.8%) and placental abruption (0.7%). When comparing among provinces, reported abortion-related maternal mortality (14.1% vs 0%) was more frequent in North Kivu than in South Kivu.

CONCLUSION

This study imperatively highlights the need for targeted interventions to reduce maternal mortality. By emphasizing the crucial importance of antenatal consultations, intrapartum/immediate post-partum care and quality of care, significant progress can be made in guaranteeing maternal health and reducing many avoidable deaths.

Prevalence of sacroiliac joint fusion in females and males depending on parity status

OBJECTIVES

Previous research shows that sacroiliac (SI) joint fusion is age and sex dependent. Older individuals-specifically starting in the fifth or sixth decade of life-are more likely to develop SI fusion. Females have a lower frequency of SI joint fusion than males, perhaps due to pregnancy or parturition. This study examines the relationship between SI joint fusion with both sex and parity status in females. The issue is whether the prevalence of SI fusion in nulliparous females is more similar to that of males or parous females.

MATERIALS AND METHODS

The sample consists of 46 nulliparous females, 119 parous females, and 158 males from the William M. Bass Donated Skeletal Collection. Ages of the individuals ranged from 50 to 89 years. Sex, age, and parity status were self-reported.

RESULTS

The frequency of SI joint fusion is significantly different among males (13.29%), nulliparous females (6.52%), and parous females (0.84%). Pairwise comparison of the three groups for SI joint fusion shows that parous females and males are significantly different, but nulliparous females are nonsignificantly different from parous females and males.

DISCUSSION

Parity status does not appear to be a factor in the sexually dimorphic nature of SI joint fusion in this sample. Rather, biomechanical and hormonal factors may have a greater contribution to higher rates of SI joint fusion in males than females.

Evolution of the human birth canal

It seems puzzling why humans have evolved such a small and rigid birth canal that entails a relatively complex process of labor compared with the birth canal of our closest relatives, the great apes. This study reviewed insights into the evolution of the human birth canal from recent theoretical and empirical studies and discussed connections to obstetrics, gynecology, and orthopedics. Originating from the evolution of bipedality and the large human brain million years ago, the evolution of the human birth canal has been characterized by complex trade-off dynamics among multiple biological, environmental, and sociocultural factors. The long-held notion that a wider pelvis has not evolved because it would be disadvantageous for bipedal locomotion has not yet been empirically verified. However, recent clinical and biomechanical studies suggest that a larger birth canal would compromise pelvic floor stability and increase the risk of incontinence and pelvic organ prolapse. Several mammals have neonates that are equally large or even larger than human neonates compared to the size of the maternal birth canal. In these species, the pubic symphysis opens widely to allow successful delivery. Biomechanical and developmental constraints imposed by bipedality have hindered this evolutionary solution in humans and led to the comparatively rigid pelvic girdle in pregnant women. Mathematical models have shown why the evolutionary compromise to these antagonistic selective factors inevitably involves a certain rate of fetopelvic disproportion. In addition, these models predict that cesarean deliveries have disrupted the evolutionary equilibrium and led to new and ongoing evolutionary changes. Different forms of assisted birth have existed since the stone age and have become an integral part of human reproduction. Paradoxically, by buffering selection, they may also have hindered the evolution of a larger birth canal. Many of the biological, environmental, and sociocultural factors that have influenced the evolution of the human birth canal vary globally and are subject to ongoing transitions. These differences may have contributed to the global variation in the form of the birth canal and the difficulty of labor, and they likely continue to change human reproductive anatomy.

Take it to the limit: The limitations of energetic explanations for birth timing in humans

A hallmark of modern humans is that our newborns are neurologically immature compared to other primates. It is disputed whether this so-called secondary altriciality evolved due to remodelling of the pelvis associated with bipedal locomotion, as suggested by the obstetrical dilemma hypothesis, or from maternal energetic limitations during pregnancy. Specifically, the 'Energetics of Gestation and Growth' (EGG) hypothesis posits that birth is initiated when foetal energy requirements exceed the maximum sustained maternal metabolic rate during pregnancy at around 2.1 × basal metabolic rate (BMR) of the non-pregnant, non-lactating condition (NPNL). However, the metabolic threshold argued under the EGG framework is derived from one study with a small sample size of only 12 women from the UK. Accordingly, we performed a meta-analysis of all published studies on metabolic scopes during pregnancy to better account for variability. After excluding 3 studies with methodological issues, a total of 12 studies with 303 women from 5 high- and 3 low-income countries were analysed. On average, pregnancy was found to be less metabolically challenging than previously suggested. The studies revealed substantial variation in metabolic scope during pregnancy, which was not reflected by variation in birth timing. Further, in a third of the studies, the metabolic rates exceeded 2.1 × BMRNPNL. Our simulation of foetal energy requirements demonstrated that this metabolic threshold of 2.1 × BMRNPNL cannot realistically be crossed by the foetus around the time of birth. These findings imply that metabolic constraints are not the main limiting factor dictating gestation length.

There is an obstetrical dilemma: Misconceptions about the evolution of human childbirth and pelvic form

Compared to other primates, modern humans face high rates of maternal and neonatal morbidity and mortality during childbirth. Since the early 20th century, this "difficulty" of human parturition has prompted numerous evolutionary explanations, typically assuming antagonistic selective forces acting on maternal and fetal traits, which has been termed the "obstetrical dilemma." Recently, there has been a growing tendency among some anthropologists to question the difficulty of human childbirth and its evolutionary origin in an antagonistic selective regime. Partly, this stems from the motivation to combat increasing pathologization and overmedicalization of childbirth in industrialized countries. Some authors have argued that there is no obstetrical dilemma at all, and that the difficulty of childbirth mainly results from modern lifestyles and inappropriate and patriarchal obstetric practices. The failure of some studies to identify biomechanical and metabolic constraints on pelvic dimensions is sometimes interpreted as empirical support for discarding an obstetrical dilemma. Here we explain why these points are important but do not invalidate evolutionary explanations of human childbirth. We present robust empirical evidence and solid evolutionary theory supporting an obstetrical dilemma, yet one that is much more complex than originally conceived in the 20th century. We argue that evolutionary research does not hinder appropriate midwifery and obstetric care, nor does it promote negative views of female bodies. Understanding the evolutionary entanglement of biological and sociocultural factors underlying human childbirth can help us to understand individual variation in the risk factors of obstructed labor, and thus can contribute to more individualized maternal care.

Sex, gender, and sexuality in paleopathology: Select current developments and pathways forward

OBJECTIVE

Overall, paleopathology trails behind related fields in exploring sex, gender, and sexuality in past societies. Here, we interrogatively synthesize scholarship on topics not included in similar reviews, focusing on sex estimation methods, and considering the social determinants of health; trauma; reproduction and family; and childhood - to highlight novel, social epidemiology- and social theory-informed frameworks and interpretive devices.

CONCLUSIONS

Many paleopathological interpretations focus on sex-gender differences relative to health, with increasing use of intersectionality. Others consistently project present-day ideologies about sex, gender, and sexuality (e.g., binary sex-gender systems) into paleopathological interpretations (i.e., presentism).

SIGNIFICANCE

Paleopathologists have an ethical imperative to generate scholarship that contributes to social justice initiatives focused on dismantling structural inequalities, especially relative to sex, gender, and sexuality (e.g., homophobia), such as through denaturalizing presentist binary systems. They also have a responsibility towards greater inclusivity relative to researcher identity and diversification of method and theory.

LIMITATIONS

In addition to material limitations complicating reconstructions of sex, gender, and sexuality relative to health and disease in the past, this review wasn't comprehensive. The review was also limited by the relative paucity of paleopathological work on these topics.

SUGGESTIONS FOR FUTURE RESEARCH

The outlook for paleopathological research on sex, gender, and sexuality is, however, positive; paleopathology is well situated to tackle these aspects of social identity. Future work should consider critical, self-reflective movement away from presentism; more robust contextualization; and further engagement with social theory and social epidemiology theory and approaches, including the Developmental Origins of Health and Disease (DOHaD), social determinants of health, and intersectionality.

A stigmatizing dilemma in the labour room: Irrationality or selfishness?

Nowadays, a considerable number of women have a negative or outright traumatic birth experience. Literature shows that being involved in decision-making and exercising autonomy are important factors in having a positive birth experience. In this article, I explore the hypothesis that some views characteristic of the biomedical model of childbirth may hinder women's involvement in decision-making, leading them to what I have dubbed as a 'stigmatizing dilemma'; that is, to be perceived and treated as either irrational or selfish when trying to exercise their autonomy in the labour room. I suggest that such a stigmatizing dilemma arises when the following views are uncritically and unqualifiedly endorsed: (1) childbirth is a process fraught with risk, particularly to babies; (2) labouring women's reports are unreliable and their subjective perspective does not constitute a valuable source of information; (3) medical knowledge and procedures are the safest means to give birth. In a scenario where (1)-(3) are strongly endorsed, if birthing women act according to instrumental rationality and want the best for their babies, they will be expected to just leave decisions to medical experts. Thus, not following expert directions might lead women to fall under the stigma of either irrationality or selfishness: they could be perceived and treated as either irrational, since they may not seem to seek the best means to accomplish their goal; or selfish, since they may seem to pursue goals other than the baby's health. I examine these stigmas in relation to two ideals: that of disembodied rationality and that of selfless motherhood. I also explore different ways in which the views and prejudices underlying this stigmatizing dilemma could be challenged.

Squatting, pelvic morphology and a reconsideration of childbirth difficulties

 

Childbirth is commonly viewed as difficult in human females, encompassed by the 'Obstetrical Dilemma' (OD) described by early palaeoanthropologists as an evolved trade-off between a narrow pelvis necessitated by bipedalism and a large-brained fetal head. The OD has been challenged on several grounds. We add to these challenges by suggesting humans likely squatted regularly during routine tasks prior to the advent of farming societies and use of seats. We suggest that habitual squatting, together with taller stature and better nutrition of ancestral hunter-gatherers compared with later Neolithic and industrial counterparts, obviated an OD. Instead, difficulties with parturition may have arisen much later in our history, accompanying permanent settlements, poorer nutrition, greater infectious disease loads and negligible squatting in daily life. We discuss bioarchaeological and contemporary data that support these viewpoints, suggest ways in which this hypothesis might be tested further and consider its implications for obstetrical practice.

Lay Summary

Human childbirth is viewed as universally difficult. Evidence from physical therapies/engineering and studies of living and ancestral humans illustrates habitual squatting widens the pelvis and could improve childbirth outcomes. Obstetrical difficulties emerged late in prehistory accompanying settled agriculture, poorer nutrition and less squatting. Specific physical exercises could improve obstetrical practice.

Ecocultural or Biocultural? Towards Appropriate Terminologies in Biocultural Diversity

Biocultural diversity has made notable contributions that have furthered our understanding of the human culture-nature interrelationship. However, the usage of the term 'biocultural' is not unique to biocultural diversity. It was first used in biocultural studies within anthropology decades ahead of biocultural diversity. The existing literature on biocultural diversity does not acknowledge the prior existence of biocultural studies, or provide a clear demarcation between usages of the two terms. In this article, I discuss the varying contexts in usage of the term 'biocultural' between biocultural diversity and biocultural anthropology. While biocultural diversity deals with the linkages between biological, cultural, and linguistic diversity, biocultural studies in anthropology deal with the deterministic influence of physical and social environment on human biology and wellbeing. In biocultural studies, 'biocultural' refers to the integration of methodically collated cultural data with biological and environmental data. 'Bio' in biocultural anthropology therefore denotes biology, unlike biocultural diversity where it refers to biodiversity. Both biocultural studies and biocultural diversity apply 'biocultural' as descriptor to generate overlapping terminologies such as 'biocultural approach'. Such a confusing scenario is not in the interest of biocultural diversity, as it would impede theoretical advancements. I propose that advocates of biocultural diversity explore its harmonies with ecoculturalism and the possibilities of suitably adapting the term 'ecoculture' in lieu of 'bioculture'. Using 'ecocultural' instead of 'biocultural' as a descriptor to coin terminologies could solve confusions arising from the expanding usage of the term 'bioculture'.

The obstetrical dilemma hypothesis: there's life in the old dog yet

The term 'obstetrical dilemma' was coined by Washburn in 1960 to describe the trade-off between selection for a larger birth canal, permitting successful passage of a big-brained human neonate, and the smaller pelvic dimensions required for bipedal locomotion. His suggested solution to these antagonistic pressures was to give birth prematurely, explaining the unusual degree of neurological and physical immaturity, or secondary altriciality, observed in human infants. This proposed trade-off has traditionally been offered as the predominant evolutionary explanation for why human childbirth is so challenging, and inherently risky, compared to that of other primates. This perceived difficulty is likely due to the tight fit of fetal to maternal pelvic dimensions along with the convoluted shape of the birth canal and a comparatively low degree of ligamentous flexibility. Although the ideas combined under the obstetrical dilemma hypothesis originated almost a century ago, they have received renewed attention and empirical scrutiny in the last decade, with some researchers advocating complete rejection of the hypothesis and its assumptions. However, the hypothesis is complex because it presently captures several, mutually non-exclusive ideas: (i) there is an evolutionary trade-off resulting from opposing selection pressures on the pelvis; (ii) selection favouring a narrow pelvis specifically derives from bipedalism; (iii) human neonates are secondarily altricial because they are born relatively immature to ensure that they fit through the maternal bony pelvis; (iv) as a corollary to the asymmetric selection pressure for a spacious birth canal in females, humans evolved pronounced sexual dimorphism of pelvic shape. Recently, the hypothesis has been challenged on both empirical and theoretical grounds. Here, we appraise the original ideas captured under the 'obstetrical dilemma' and their subsequent evolution. We also evaluate complementary and alternative explanations for a tight fetopelvic fit and obstructed labour, including ecological factors related to nutrition and thermoregulation, constraints imposed by the stability of the pelvic floor or by maternal and fetal metabolism, the energetics of bipedalism, and variability in pelvic shape. This reveals that human childbirth is affected by a complex combination of evolutionary, ecological, and biocultural factors, which variably constrain maternal pelvic form and fetal growth. Our review demonstrates that it is unwarranted to reject the obstetrical dilemma hypothesis entirely because several of its fundamental assumptions have not been successfully discounted despite claims to the contrary. As such, the obstetrical dilemma remains a tenable hypothesis that can be used productively to guide evolutionary research.

Maternal physical, socioeconomic, and demographic characteristics and childbirth complications in rural lowland Nepal: Applying an evolutionary framework to understand the role of phenotypic plasticity

OBJECTIVES

Evolutionary perspectives on human childbirth have primarily focused on characteristics of our species in general, rather than variability within and between contemporary populations. We use an evolutionary framework to explore how physical and demographic characteristics of mothers shape the risks of childbirth complications in rural lowland Nepal, where childbearing typically commences in adolescence and chronic undernutrition is widespread, though maternal overweight is increasing in association with nutrition transition.

METHODS

We conducted secondary analyses of data from a cluster-randomized trial. Women aged 14-35 years were categorized by age, number of previous pregnancies, height, body mass index (BMI), husband's education, and household wealth. Multivariable logistic regression models tested whether these characteristics independently predicted risks of episiotomy and cesarean section (CS, n = 14 261), and obstructed labor (OL, n = 5185).

RESULTS

Risks were greatest among first-time adolescent mothers, though associations with age varied by outcome. Independent of age and parity, short stature and high BMI increased risks of CS and OL, whereas associations were weaker for episiotomy. Male offspring had increased risk of CS and OL but not episiotomy. Wealth was not associated with OL, but lower wealth and lower husband's education were associated with lower likelihood of episiotomy and CS.

CONCLUSIONS

At the individual level, the risk childbirth complications is shaped by trade-offs between fertility, growth, and survival. Some biological markers of disadvantage (early childbearing, short stature) increased the risk, whereas low socio-economic status was associated with lower risk, indicating reduced access to relevant facilities. Independent of these associations, maternal age showed complex effects.

Intersectionality and trauma analysis in bioarchaeology

Intersectionality, the theory named by Kimberlé Crenshaw, outlines how multiple elements of an individual's social identity overlap to create and preserve societal inequalities and discrimination. Recently bioarchaeology's engagement with intersectionality has become increasingly explicit, as the field recognizes the lived experience of multiple axes of an individual's identity. Evidence of trauma can remain observable in an individual's skeleton for years, making it an ideal subject of study for intersectional analyses in bioarchaeology. Using contrasting case studies of two individuals who died in hospitals and were unclaimed after death, we explore the theoretical and methodological application of intersectionality to investigations of accidental and interpersonal trauma. Differences in identities and structural inequalities affect bone quality and health outcomes. As we demonstrate, a broken bone is the intersecting result of biological, histomorphological, sociocultural, and behavioral factors. This approach allows for a better acknowledgement of the inherent complexity of past lives, elevating and amplifying previously silenced voices. In this way, intersectionality in bioarchaeology demands social justice.

Care of Infants in the Past: Bridging evolutionary anthropological and bioarchaeological approaches

The importance of care of infants and children in palaeoanthropological and human behavioural ecological research on the evolution of our species is evident in the diversity of research on human development, alloparental care, and learning and social interaction. There has been a recent surge of interest in modelling the social implications of care provision for people with serious disabilities in bioarchaeology. However, there is a lack of acknowledgement of infant and child care in bioarchaeology, despite the significant labour and resources that are required, and the implications this has for health outcomes within societies. Drawing on the recent proliferation of studies on infancy and childhood in evolutionary anthropology and bioarchaeology, this paper presents ways the subdisciplines may draw on research developments from each field to advance a more holistic understanding of the evolutionary, social and health significance of infant and children care in the past.

Sexual dimorphism of the relationship between the gut and pelvis in humans

OBJECTIVES

Obstetric demands have long been considered in the evolution of the pelvis, yet consideration of the interaction of pregnancy, the pelvis, and the gastrointestinal tract (gut) is lacking. Here, we explore sex differences in the relationship of gut volume with body size and pelvic dimensions.

MATERIALS AND METHODS

Computed tomography (CT) scans of living adult Homo sapiens (46 females and 42 males) were obtained to measure in vivo gut volume (GV) and to extract 3D models of the pelvis. We collected 19 3D landmarks from each pelvis model to acquire pelvic measurements. We used ordinary least squares regression to explore relationships between GV and body weight, stature, and linear pelvic dimensions.

RESULTS

The gut-pelvis relationship differs between males and females. Females do not exhibit significant statistical correlations between GV and any variable tested. GV correlates with body size and pelvic outlet size in males. GV scales with negative allometry relative to body weight, stature, maximum bi-iliac breadth, inferior transverse outlet breadth, and bispinous distance in males.

DISCUSSION

The lack of association between GV and body size in females may be due to limits imposed by the anticipation of accommodating a gravid uterus and/or the increased plasticity of the pelvis. The pattern of relationship between GV and the pelvic outlet suggests the role of the bony pelvis in supporting the adominal viscera in females may be small relative to its role in childbirth. We conclude that gut size inference in fossil hominins from skeletal proxies is limited and confounded by sexual dimorphism.

Weaker bones and white skin as adaptions to improve anthropological "fitness" for northern environments

The vitamin D paradox relates to the lower risk of osteoporosis in people of sub-Saharan African ancestry (Blacks) compared with people of European ancestry (Whites). The paradox implies that for bone health, Blacks require less vitamin D and calcium than Whites do. Why should populations that migrated northward out of Africa have ended up needing more vitamin D than tropical Blacks? Human skin color became lighter away from the tropics to permit greater skin penetration of the UVB light that generates vitamin D. Lack of vitamin D impairs intestinal calcium absorption and limits the amount of calcium that can deposit into the protein matrix of bone, causing rickets or osteomalacia. These can cause cephalopelvic disproportion and death in childbirth. Whiter skin was more fit for reproduction in UV-light restricted environments, but natural selection was also driven by the phenotype of bone per se. Bone formation starts with the deposition of bone-matrix proteins. Mineralization of the matrix happens more slowly, and it stiffens bone. If vitamin D and/or calcium supplies are marginal, larger bones will not be as fully mineralized as smaller bones. For the same amount of mineral, unmineralized or partially mineralized bone is more easily deformed than fully mineralized bone. The evidence leads to the hypothesis that to minimize the soft bone that causes pelvic deformation, a decrease in amount of bone, along with more rapid mineralization of osteoid improved reproductive fitness in Whites. Adaptation of bone biology for reproductive fitness in response to the environmental stress of limited availability of vitamin D and calcium came at the cost of greater risk of osteoporosis later in life.

Commingled crypts: Comparative health among Byzantine monastics in the Levant

OBJECTIVES

Early Byzantine (A.D. 330-842) monastic rules stipulated that entrants relinquished familial connections, personal belongings and secular relationships to become part of the ascetic collective that continued in death, resulting in bioarchaeological marginalization, as was the case of the monastics excavated from the Chapel of Robebus at Mount Nebo, Jordan (ca. A.D. 491-640). It was hypothesized that compared to contemporary monastic groups, the Mount Nebo monastics experienced poorer health and gravitated to Mount Nebo, owing to its association with the Prophet Moses and proximity to the Dead Sea, Livias baths and Jordan River, all associated with curative benefits, especially for those suffering from leprosy.

MATERIALS AND METHODS

The commingled remains of 73 adult males from Mount Nebo and the articulated skeletons (n = 27) from the Sanctuary of Agios Lot at Deir 'Ain 'Abata (Jordan) were assessed for paleopathology, then compared with a contemporary commingled group from the Monastery of Saint Euthymius at Khan-el-Ahmar (Judean Desert) (n = 117).

RESULTS

No skeletal evidence of leprosy was observed among the groups. Most Mount Nebo individuals did not reach an older age, yet injuries, severe osteoarthritis, lower leg osteoperiostitis and antemortem tooth loss were common. The paleopathological profile was similar at Deir 'Ain 'Abata, but paleopathology was negligible at Khan-el-Ahmar.

CONCLUSIONS

The similar paleopathological profiles of the Jordanian monastic groups suggest that the proximity to the Dead Sea may have attracted monastics to both sites, in addition to spirituality, but leprosy was not a factor based on the skeletal evidence.

Could consanguineous marriage provide a cultural alleviation for the obstetric dilemma?

In placental mammals, a poor fit between the physical dimensions of the fetus and maternal pelvis increases the likelihood of obstructed labour. This problem is especially relevant to humans, as our species demonstrates both unique adaptations in pelvic shape and structure associated with bipedalism, and fetal encephalization. Natural selection is expected to have favoured adaptations that reduce the chances of such mismatch within individual mother-offspring dyads. Here, I hypothesise that the cultural practice of consanguineous marriage may have been favoured, on account of increasing the genetic similarity between mothers and offspring and hence the correlation between maternal and fetal physical dimensions. These benefits could be amplified if consanguineous marriage was accompanied by assortative mating for height. An additional benefit of consanguineous marriage for childbirth is the slight reduction in birth size of such offspring compared to non-consanguineous unions. Although the offspring of consanguineous unions have elevated risks of morbidity and mortality, these risks are moderate and the practice could still have been favoured by selection if the reduction in maternal mortality was greater than the increased mortality among individual offspring. This hypothesis could be tested directly by investigating whether rates of obstructed labour are lower in individuals and populations practising consanguineous marriage. At a broader level, phylogenetic analysis could be conducted to test whether consanguineous marriage appears to have originated in the areas where intensive agriculture was first practiced, as adult height typically fell in such populations, potentially exacerbating the risk of obstructed labour.

Virtual histological assessment of the prenatal life history and age at death of the Upper Paleolithic fetus from Ostuni (Italy)

The fetal remains from the Ostuni 1 burial (Italy, ca 27 ka) represent a unique opportunity to explore the prenatal biological parameters, and to reconstruct the possible patho-biography, of a fetus (and its mother) in an Upper Paleolithic context. Phase-contrast synchrotron X-ray microtomography imaging of two deciduous tooth crowns and microfocus CT measurements of the right hemimandible of the Ostuni 1b fetus were performed at the SYRMEP beamline and at the TomoLab station of the Elettra - Sincrotrone laboratory (Trieste, Italy) in order to refine age at death and to report the enamel developmental history and dental tissue volumes for this fetal individual. The virtual histology allowed to estimate the age at death of the fetus at 31–33 gestational weeks. Three severe physiological stress episodes were also identified in the prenatal enamel. These stress episodes occurred during the last two months and half of pregnancy and may relate to the death of both individuals. Compared with modern prenatal standards, Os1b’s skeletal development was advanced. This cautions against the use of modern skeletal and dental references for archaeological finds and emphasizes the need for more studies on prenatal archaeological skeletal samples.

Developmental evidence for obstetric adaptation of the human female pelvis

The bony pelvis of adult humans exhibits marked sexual dimorphism, which is traditionally interpreted in the framework of the "obstetrical dilemma" hypothesis: Giving birth to large-brained/large-bodied babies requires a wide pelvis, whereas efficient bipedal locomotion requires a narrow pelvis. This hypothesis has been challenged recently on biomechanical, metabolic, and biocultural grounds, so that it remains unclear which factors are responsible for sex-specific differences in adult pelvic morphology. Here we address this issue from a developmental perspective. We use methods of biomedical imaging and geometric morphometrics to analyze changes in pelvic morphology from late fetal stages to adulthood in a known-age/known-sex forensic/clinical sample. Results show that, until puberty, female and male pelves exhibit only moderate sexual dimorphism and follow largely similar developmental trajectories. With the onset of puberty, however, the female trajectory diverges substantially from the common course, resulting in rapid expansion of obstetrically relevant pelvic dimensions up to the age of 25-30 y. From 40 y onward females resume a mode of pelvic development similar to males, resulting in significant reduction of obstetric dimensions. This complex developmental trajectory is likely linked to the pubertal rise and premenopausal fall of estradiol levels and results in the obstetrically most adequate pelvic morphology during the time of maximum female fertility. The evidence that hormones mediate female pelvic development and morphology supports the view that solutions of the obstetrical dilemma depend not only on selection and adaptation but also on developmental plasticity as a response to ecological/nutritional factors during a female's lifetime.