James W. Wood

A draft genome of Yersinia pestis from victims of the Black Death

Technological advances in DNA recovery and sequencing have drastically expanded the scope of genetic analyses of ancient specimens to the extent that full genomic investigations are now feasible and are quickly becoming standard. This trend has important implications for infectious disease research because genomic data from ancient microbes may help to elucidate mechanisms of pathogen evolution and adaptation for emerging and re-emerging infections. Here we report a reconstructed ancient genome of Yersinia pestis at 30-fold average coverage from Black Death victims securely dated to episodes of pestilence-associated mortality in London, England, 1348–1350. Genetic architecture and phylogenetic analysis indicate that the ancient organism is ancestral to most extant strains and sits very close to the ancestral node of all Y. pestis commonly associated with human infection. Temporal estimates suggest that the Black Death of 1347–1351 was the main historical event responsible for the introduction and widespread dissemination of the ancestor to all currently circulating Y. pestis strains pathogenic to humans, and further indicates that contemporary Y. pestis epidemics have their origins in the medieval era. Comparisons against modern genomes reveal no unique derived positions in the medieval organism, indicating that the perceived increased virulence of the disease during the Black Death may not have been due to bacterial phenotype. These findings support the notion that factors other than microbial genetics, such as environment, vector dynamics and host susceptibility, should be at the forefront of epidemiological discussions regarding emerging Y. pestis infections.

Women's Reproductive Cancers in Evolutionary Context

Reproductive experiences for women in todays affluent Western nations differ from those of women in hunting and gathering societies, who continue the ancestral human pattern. These differences parallel commonly accepted reproductive risk factors for cancers of the breast, endometrium and ovary. Nutritional practices, exercise requirements, and body composition are nonreproductive influences that have been proposed as additional factors affecting the incidence of womens cancers. In each case, these would further increase risk for women in industrialized countries relative to forager women. Lifestyles and reproductive patterns new from an evolutionary perspective may promote womens cancer. Calculations based on a theoretical model suggest that, to age 60, modern Western women have a breast cancer risk as much as 100 times that of preagricultural women.

Declining fecundity and ovarian ageing in natural fertility populations

Worldwide, human fertility declines with increasing maternal age, after contraceptive-use patterns and behavioral factors are taken into consideration. Here, we summarize some of our theoretical and empirical work examining the biological factors contributing to this age pattern of fertility. We undertook an 11 month prospective endocrinological study in a natural fertility (non-contracepting) population (rural Bangladesh) to estimate the contributions of fetal loss and fecundability (the probability of conception) to declining fecundity with age. Prospective interviews and urine samples for pregnancy tests were collected twice weekly from up to 700 women. These data were used to test mathematical models of the underlying biological processes contributing to changing fecundability and fetal loss risk with maternal age. The results indicate that much of the decline in fecundity can be attributed to an increasing risk of fetal loss with maternal age. Much of this fetal loss is due to chromosomal abnormalities--a result of ageing oocytes. Fecundability, on the other hand, does not begin to decline until the early 40s. We hypothesize that this is also a result of ageing at the ovarian level, namely follicular atresia, in the years just prior to menopause. The irregularity of menstrual cycles--longer cycles and increasingly variable hormonal patterns--at these ages may be a direct result of the small and rapidly dwindling remaining pool of follicles. We present a simple mathematical model of this process, and some preliminary laboratory results that support the model.

Fertility in Traditional Societies

This chapter is a preliminary attempt to characterise reproductive patterns in traditional, pre-industrial societies, including huntergatherers, tribal horticulturalists and pastoralists and settled peasant agriculturalists. Assertions about the level of fertility in such societies have played a key role in the development of theoretical models in demography and anthropology and, more recently, in reproductive biology. In classic demographic transition theory, for example, it was assumed that pre-transitional societies were characterised by uniformly high fertility rates, which provided the starting point for the recent secular decline in fertility (Knodel, 1977). Most ecological anthropologists, in contrast, have come to believe that many traditional societies, especially unacculturated hunter-gatherers, have regulated their reproductive output at relatively low levels (Dumond, 1975; Peacock, 1986). It has even been suggested that there occurred an earlier, stone-age demographic transition toward higher. birth and death rates associated with the emergence of settled village life during the Neolithic (Handwerker, 1983; Roth, 1985).1

A Theory of Preindustrial Population Dynamics Demography, Economy, and Well‐Being in Malthusian Systems

This paper presents a simple model of preindustrial population dynamics, one that brings together the theoretical insights of Thomas Robert Malthus and Ester Boserup. Central to the model is the concept of well‐being, which refers to those aspects of physical condition that influence an individuals capacity to survive and reproduce. Changes in the mean and variance in well‐being are modeled, first, under a fixed system of food production and, second, in the face of subsistence change. Among other things, the model suggests that the long‐term effects of economic change on the distribution of well‐being are negligible, although both the mean and variance are likely to increase temporarily in the short run. The model is used to explore several issues of enduring importance to demographic anthropology, including the nature of population regulation, the relationship between population pressure and economic change, and the demographic consequences of the transition from hunting and gathering to settled agriculture.

Selectivity of Black Death mortality with respect to preexisting health

Was the mortality associated with the deadliest known epidemic in human history, the Black Death of 1347–1351, selective with respect to preexisting health conditions (“frailty”)? Many researchers have assumed that the Black Death was so virulent, and the European population so immunologically naïve, that the epidemic killed indiscriminately, irrespective of age, sex, or frailty. If this were true, Black Death cemeteries would provide unbiased cross-sections of demographic and epidemiological conditions in 14th-century Europe. Using skeletal remains from medieval England and Denmark, new methods of paleodemographic age estimation, and a recent multistate model of selective mortality, we test the assumption that the mid-14th-century Black Death killed indiscriminately. Skeletons from the East Smithfield Black Death cemetery in London are compared with normal, nonepidemic cemetery samples from two medieval Danish towns (Viborg and Odense). The results suggest that the Black Death did not kill indiscriminately—that it was, in fact, selective with respect to frailty, although probably not as strongly selective as normal mortality.

Urinary Estrone Conjugate and Pregnanediol 3-Glucuronide Enzyme Immunoassays for Population Research

BACKGROUND Monitoring of reproductive steroid hormones at the population level requires frequent measurements, hormones or metabolites that remain stable under less than ideal collection and storage conditions, a long-term supply of antibodies, and assays useful for a range of populations. We developed enzyme immunoassays for urinary pregnanediol 3-glucuronide (PDG) and estrone conjugates (E1Cs) that meet these criteria. METHODS Enzyme immunoassays based on monoclonal antibodies were evaluated for specificity, detection limit, parallelism, recovery, and imprecision. Paired urine and serum specimens were analyzed throughout menstrual cycles of 30 US women. Assay application in different populations was examined with 23 US and 42 Bangladeshi specimens. Metabolite stability in urine was evaluated for 0-8 days at room temperature and for 0-10 freeze-thaw cycles. RESULTS Recoveries were 108% for the PDG assay and 105% for the E1C assay. Serially diluted specimens exhibited parallelism with calibration curves in both assays. Inter- and intraassay CVs were <11%. Urinary and serum concentrations were highly correlated: r = 0.93 for E1C-estradiol; r = 0.98 for PDG-progesterone. All Bangladeshi and US specimens were above detection limits (PDG, 21 nmol/L; E1C, 0.27 nmol/L). Bangladeshi women had lower follicular phase PDG and lower luteal phase PDG and E1Cs than US women. Stability experiments showed a maximum decrease in concentration for each metabolite of <4% per day at room temperature and no significant decrease associated with number of freeze-thaw cycles. CONCLUSIONS These enzyme immunoassays can be used for the field conditions and population variation in hormone metabolite concentrations encountered in cross-cultural research.

A Model of Age-specific Fecundability

A new model of the behavioural and physiological causes of age-specific variation in marital fecundability is presented. Total fecundability is decomposed into a series of susceptibility factors (the length of ovarian cycles, the length of the fertile period within each cycle, the probability that a cycle is ovulatory, and the likelihood that an act of unprotected intercourse within the fertile period results in conception) and an exposure factor reflecting the effect of duration of marriage on coital frequency. The impact of intra-uterine mortality on effective fecundability is also modelled. Data on western women, from which standard age curves of fecundability are estimated, suggest that any decline in fecundity between ages 30 and 40 is attributable to changes, not in the ability to conceive, but in the capacity to carry a pregnancy to term. Sensitivity tests suggest that the most important potential sources of inter-population variation in fecundability are intra-uterine death and the incidence of an...

Lactation and birth spacing in highland New Guinea.

The effects of infant suckling patterns on the post-partum resumption of ovulation and on birth spacing are investigated among the Gainj of highland New Guinea. Based on hormonal evidence the median duration of lactational anovulation is 20.4 months accounting for about 75% of the median interval between live birth and next successful conception (i.e. resulting in live birth). Throughout lactation suckling episodes are short and frequent the interval changing slowly over time from 24 minutes in newborns to 80 minutes in 3-year olds. Maternal serum prolactin concentrations decline in parallel with the changes in suckling patterns approaching the level observed in non-nursing women by about 24 months postpartum. A path analysis indicates that the interval between suckling episodes is the principal determinant of maternal prolactin concentration with time since parturition affecting prolactin secretion only in so far as it affects suckling frequency. The extremely prolonged contraceptive effect of breastfeeding in this population thus appears to be due to 1) a slow decline in suckling frequency with time since parturition; and 2) absence of a decline over time in hypothalamic-pituitary responsiveness to the suckling stimulus. (authors modified)

The Osteological Paradox Reconsidered

ter, and Sontz I97I; Gallagher I977; Hayden I977, I979) that the rules may be so lax (at least with regard to the overall morphology of the lithic artifacts) that the archaeologist may be unable to ascertain from the lithics that they were made according to such rules. I suspect (although I do not speak as a lithics specialist) that we recognize the symbolic nature of the archaeological record of early Upper Paleolithic Europe more from its decorative and representational art than from its lithics. Nevertheless, I am in complete agreement with Byerss interpretation of the Middle-to-Upper-Paleolithic transition in Europe with the one exception that there are more kinds or levels of symbolic behavior than he mentions and that the origins of language are as important to understand as the origins of symbolic culture. Above all, I am encouraged to see a scholar from outside Paleolithic archaeology taking a serious and anything but naive interest in what archaeology has to offer. If we archaeologists can return the compliment by taking a serious and ideally not too naive interest in what other disciplines have to tell us about the evolution of human culture and of the human mind, our discipline will benefit enormously.