Perinatal mortality at pre-Columbian Teotihuacan

The skeletal population of 166 individuals from a low-status apartment compound of the pre-Columbian city of Teotihuacan contained 52 perinatal individuals. The most perilous time of the lifespan was around birth, as revealed by life table analysis. Femur length was not increasing during the last month of gestation, and individuals were probably shorter somatically at birth than modern standards or historic-period Arikara skeletal controls. The possibility of intrauterine growth retardation is investigated through paleo-pathological indicators of prenatal growth arrest. The evidence of prenatal stress and the high rate of mortality at birth seem to indicate that this New World preindustrial urban population faced similar health and nutritional stresses as Old World preindustrial cities.     

American Indian Population Recovery following Smallpox Epidemics

Scholars generally agree that American Indian populations were reduced substantially following European contact by a variety of Old World diseases. However, scholarly attention has been devoted almost exclusively to ascertaining mortality during smallpox and other disease episodes and its impact on population size, as typified in "working backwards" to ascertain earlier population size. American Indian populations were dynamic entities, and were constantly changing as members were born, died, or migrated, even if population size from one year to the next was relatively constant. The interaction of disease, mortality, and fertility as well as the age structure of mortality and resulting rates of population growth influenced changes in American Indian population size following experiences with any particular disease. These factors operated to produce either greater or lesser declines than simple mortality rates would suggest. This article presents simulations developed to understand changes in American Indian population size following hypothetical episodes of smallpox.     

Estimating mortality in skeletal populations: influence of the growth rate on the interpretation of levels and trends during the transition to agriculture

Traditional paleodemographic methods of estimating mortality have been based on unrealistic assumptions about the prevalence of closed and stationary populations. When a living closed population was growing, the mean age at death of its skeletal survivors will be shifted below its true life expectancy. For declining populations, the mean age at death will be higher than true underlying life expectancy at birth. The faster the rate of growth, the larger and more curvilinear is the displacement. Mortality estimates can only be extracted from skeletal populations via an independent estimate of the growth rate. Fertility levels, however, can be estimated directly. The empirical importance of growth rate-dependent mortality estimates is demonstrated by reinterpreting mean-age-at-death data from several populations before and after the agricultural revolution; with detailed consideration given to the Old World populations of Acsadi and Nemeskeri and a New World population from central Illinois.     

On the number of New World founders: a population genetic portrait of the peopling of the Americas

The founding of New World populations by Asian peoples is the focus of considerable archaeological and genetic research, and there persist important questions on when and how these events occurred. Genetic data offer great potential for the study of human population history, but there are significant challenges in discerning distinct demographic processes. A new method for the study of diverging populations was applied to questions on the founding and history of Amerind-speaking Native American populations. The model permits estimation of founding population sizes, changes in population size, time of population formation, and gene flow. Analyses of data from nine loci are consistent with the general portrait that has emerged from archaeological and other kinds of evidence. The estimated effective size of the founding population for the New World is fewer than 80 individuals, approximately 1% of the effective size of the estimated ancestral Asian population. By adding a splitting parameter to population divergence models it becomes possible to develop detailed portraits of human demographic history. Analyses of Asian and New World data support a model of a recent founding of the New World by a population of quite small effective size.     

Neonatal size and infant mortality at high altitude in the western Himalaya

A prospective study was undertaken in Ladakh, India, a high-altitude region of the Himalaya, to investigate the effects of small average birth size on neonatal mortality. While such studies exist from high-altitude regions of the New World and shed light on the adaptive status of high-altitude-dwelling populations there, this is the first to examine this relationship in the Himalaya. In a sample of 168 newborns, birthweight and other anthropometric measurements were reduced relative to Andean and Tibetan newborns. Logistic regression and hazard analysis showed that neonatal biological characteristics such as weight, fatness, and circumferences were important predictors of survival probabilities of infants, especially in the neonatal period. Low Rohrer's Ponderal Index (PI) was particularly strongly related to poor survival outcome. Males and females showed no significant differences in mortality risk. Data derived from reproductive histories revealed that neonatal mortality accounted for 70–80% of total infant mortality in Ladakh. Compared to other high-altitude studies, small newborn size in Ladakh was associated with much higher mortality risks; mortality risk rose dramatically with birthweights below the mean (2,764 grams), which characterized 50% of all newborns. It is argued that newborns in Ladakh are subject to strong directional selective forces that favor higher birthweights that incur lower risks of neonatal mortality, while Andean infants are subject to relatively mild selection pressure at both ends of the birthweight distribution. Given the overall small size at birth of Ladakhi newborns and the poor survival outcomes of newborns below the mean, it is suggested that this population is less well adapted in a biological sense to the stresses inherent in this high-altitude environment than are Andean populations, perhaps due to the relatively recent colonization of the area and the substantial genetic admixture that has occurred in the past. © 1994 Wiley-Liss, Inc.     

Population genetics of New World screwworm from the Caribbean: insights from microsatellite data

Abstract.  Diseases affecting livestock can have a significant impact on animal productivity and on trade of live animals, meat and other animal products, which, consequently, affects the overall process of economic development. The New World screwworm, Cochliomyia hominivorax (Coquerel) (Diptera: Calliphoridae), is an important parasitic insect pest in Neotropical regions. This species has been successfully eradicated from North and most of Central America by the sterile insect technique, but continues to affect the development of the livestock sector in most Caribbean economies. Here, we provide some insight into the patterns of genetic variation and structure and gene flow of C. hominivorax populations from the Caribbean. Analysis of populations from 10 geographical sites in four islands revealed a moderate genetic variability within the populations. Surprisingly, a high population differentiation was found even in intra-island comparisons between populations. This observation can reflect either highly structured populations resulting from a lack of gene flow or a source–sink dynamic. Our study also suggests that New World screwworm populations can recover very rapidly from population contractions. This is valuable information that should be required prior to any investment in large-scale efforts aiming at controlling this pest.     

Demography and genetics suggest reversal of dolphin source‐sink dynamics,with implications for conservation

The forecast for the viability of populations depends upon metapopulation dynamics: the combination of reproduction and mortality within populations, as well as dispersal between populations. This study focuses on an Indo‐Pacific bottlenose dolphin (Tursiops aduncus) population in coastal waters near Bunbury, Western Australia. Demographic modeling of this population suggested that recent reproductive output was not sufficient to offset mortality. Migrants from adjacent populations might make up this deficit, so that Bunbury would act as a “sink,” or net recipient population. We investigated historical dispersal in and out of Bunbury, using microsatellites and mitochondrial DNA of 193 dolphins across five study locations along the southwestern Australian coastline. Our results indicated limited gene flow between Bunbury and adjacent populations. The data also revealed a net‐dispersal from Bunbury to neighboring populations, with microsatellites showing that more than twice as many individuals per generation dispersed out of Bunbury than into Bunbury. Therefore, in historic times, Bunbury appears to have acted as a source population, supporting nearby populations. In combination with the prior finding that Bunbury is currently not producing surplus offspring to support adjacent populations, this potential reversal of source‐sink dynamics may have serious conservation implications for Bunbury and other populations nearby.     

Stable Isotopes and Zooarchaeology at Teotihuacan,Mexico Reveal Earliest Evidence of Wild Carnivore Management in Mesoamerica

From Roman gladiatorial combat to Egyptian animal mummies, the capture and manipulation of carnivores was instrumental in helping to shape social hierarchies throughout the ancient world. This paper investigates the historical inflection point when humans began to control animals not only as alimental resources but as ritual symbols and social actors in the New World. At Teotihuacan (A.D. 1–550), one of the largest pre-Hispanic cities, animal remains were integral components of ritual caches expressing state ideology and militarism during the construction of the Moon and the Sun Pyramids. The caches contain the remains of nearly 200 carnivorous animals, human sacrificial victims and other symbolic artifacts. This paper argues the presence of skeletal pathologies of infectious disease and injuries manifest on the carnivore remains show direct evidence of captivity. Stable isotope analysis (δ¹³C and δ¹⁵N) of bones and teeth confirms that some of these carnivores were consuming high levels of C₄ foods, likely reflecting a maize-based anthropocentric food chain. These results push back the antiquity of keeping captive carnivores for ritualistic purposes nearly 1000 years before the Spanish conquistadors described Moctezuma’s zoo at the Aztec capital. Mirroring these documents the results indicate a select group of carnivores at Teotihuacan may have been fed maize-eating omnivores, such as dogs and humans. Unlike historical records, the present study provides the earliest and direct archaeological evidence for this practice in Mesoamerica. It also represents the first systematic isotopic exploration of a population of archaeological eagles (n = 24) and felids (n = 29).     

Population‐specific deviations of global human craniometric variation from a neutral model

Past studies have revealed that much of human craniometric variation follows a neutral model of population relationships. At the same time, there is evidence for the influence of natural selection in having shaped some global diversity in craniometrics. In order to partition these effects, and to explore other potential population‐specific influences, this article analyzes residuals of craniometric distances from a geographically based neutral model of population structure. W.W. Howells' global craniometric data set was used for these analyses, consisting of 57 measurements for 22 populations around the world, excluding Polynesia and Micronesia because of the relatively recent settlement of these regions. Phenotypic and geographic distances were derived between all pairs of populations. Three‐dimensional multidimensional scaling configurations were obtained for both distance matrices, and compared using a Procrustes rotation method to show which populations do not fit the geographic model. This analysis revealed three major deviations: the Buriat, Greenland Inuit, and Peru. The deviations of the Buriat and Greenland Inuit appear to be related to long‐term adaptation to cold environments. The Peruvian sample is more similar to other New World populations than expected based on geographic distance alone. This deviation likely reflects the evolutionarily recent movement of human populations into South America, such that these populations are further from genetic equilibrium. This same pattern is seen in South American populations in a comparative analysis of classical genetic markers, but not in a comparative analysis of STR loci, perhaps reflecting the higher mutation rate for the latter. Am J Phys Anthropol, 2010. © 2009 Wiley‐Liss, Inc.     

Low levels of STRP variability are not universal in American Indians

Data related to 15 short tandem repeat polymorphisms (STRPs) are reported for five Brazilian Indian populations, and a set of them compared with results previously reported for Asian, neo-Brazilian, North American, Iberian, and African populations. The low variability observed for these markers among the Suruí Indians is confirmed, but the other populations show variability levels that are similar to those found elsewhere. Previous suggestions of population bottlenecks in the prehistorical colonization of the New World were not confirmed. On the other hand, STRPs again showed to be good markers for the establishment of population relationships.     

Predators reverse the direction of density dependence for juvenile salmon mortality

The effect of predators on prey populations depends on how predator-caused mortality changes with prey population density. Predators can enforce density-dependent prey mortality and contribute to population stability, but only if they have a positive numerical or behavioral response to increased prey density. Otherwise, predator saturation can result in inversely density-dependent mortality, destabilizing prey populations and increasing extinction risk. Juvenile salmon and trout provide some of the clearest empirical examples of density-dependent mortality in animal populations. However, although juvenile salmon are very vulnerable to predators, the demographic effects of predators on juvenile salmon are unknown. We tested the interactive effects of predators and population density on the mortality of juvenile Atlantic salmon (Salmo salar) using controlled releases of salmon in natural streams. We introduced newly hatched juvenile salmon at three population density treatments in six study streams, half of which contained slimy sculpin (Cottus cognatus), a common generalist predator (18 release sites in total, repeated over two summers). Sculpin reversed the direction of density dependence for juvenile salmon mortality. Salmon mortality was density dependent in streams with no sculpin, but inversely density dependent in streams where sculpin were abundant. Such predator-mediated inverse density dependence is especially problematic for prey populations suppressed by other factors, thereby presenting a fundamental challenge to persistence of rare populations and restoration of extirpated populations.     

Demography, life history, and social structure in Propithecus diadema edwardsi from 1986-2000 in Ranomafana National Park, Madagascar

Prosimian lemurs differ fundamentally from anthropoid primates in many traits related to social structure. By exploring the demography of Milne-Edwards' sifakas (Propithecus diadema edwardsi), and comparing it to other well-studied primates, we explore the effect of demographic and life-history factors on social structure. Specifically, we compare lemur survivorship and fertility patterns to two published composite models: one created for New World and another created for Old World monkeys. Using longitudinal data collected on individual Propithecus diadema edwardsi from four study groups from 1986-2000 in Ranomafana National Park, Madagascar, we quantify 1) group composition, 2) birth seasonality, 3) interbirth interval, 4) life-table values, and 5) population growth estimates. The mortality, survivorship, and life-expectancy schedules indicate high infant and juvenile mortality. Fertility remains high until death. The intrinsic rate of increase and net reproductive rate indicate a shrinking population. We suggest that high mortality rather than low fertility causes the observed population decline. While sifaka survivorship closely resembles New World patterns, fertility resembles Old World patterns, i.e., like New World monkeys, few sifakas survive to reproductive age, and those that do, reproduce at a slow rate resembling the Old World pattern. This necessarily impacts social structure. An adult sifaka at the end of her lifespan will have one only daughter who survives to reproductive age, compared to 3.4 for New World or 2.7 for Old World monkeys. Demography limits the formation of large kin-based groups for sifakas, and survivorship and fertility patterns do not easily permit sifakas to form large same-sex family groups.     

Digital dermatoglyphic patterns of Eskimo and Amerindian populations: relationships between geographic, dermatoglyphic, genetic, and linguistic distances.

Dermatoglyphic traits have been used to assess population affinities and structure. Here, we describe the digital patterns of four Eskimo populations from Alaska: two Yupik-speaking villages from St. Lawrence Island and two Inupik groups presently residing on mainland Alaska. For a broader evolutionary perspective, these four Eskimo populations are compared to other Inuit groups, to North American Indian populations, and to Siberian aggregates. The genetic structures of 18 New and Old World populations were explored using R-matrix plots and Wright's FST values. The relationships between dermatoglyphic, blood genetic, geographic, and linguistic distances were assessed by comparing matrices through Mantel correlations and through partial and multiple correlations. Statistically significant relationships between dermatoglyphics and genetics, genetics and geography, and geography and language were revealed. In addition, significant correlations between dermatoglyphics and geography, with linguistic variation constant, were noted for females but not for males. These results attest to the usefulness of dermatoglyphics in resolving various evolutionary questions concerning normal human variation.     

Predator-driven component Allee effects in a wild ungulate

Negative density dependence is an important driver of population dynamics of large vertebrates. Allee effects (positive density dependence), however, can affect small populations. Allee effects can be generated by predation and recent research has revealed potentially important indirect effects of predation on population dynamics. For wild populations, however, quantification of both Allee effects and indirect effects of predation remains scarce. We monitored for 27 years a bighorn sheep (Ovis canadensis) population that declined dramatically as episodes of cougar (Puma concolor) predation depressed survival. Predation led to a positive relationship between lamb survival and population size below a threshold, and to an overall positive relationship between yearling and adult ewe survival and population size. During years of high predation, lambs also suffer mortality through reduced growth, contributing a third of the total impact of predation on lamb survival. There was no positive association between population growth and population size, probably because growth was affected by several factors other than predation, including disease. Our results support the contention that predator-driven component Allee effects may exacerbate the effects of other environmental drivers and increase the risk of extinction of small populations.     

Demography of the Juang tribal population of Orissa

Demographic analysis of genealogical data collected in 1954 for 23 Juang villages was undertaken employing indirect estimation techniques and computer projection methodology. Results indicated that this group did not feature the historically high fertility levels associated with Indian tribal groups, although fertility was higher than previously reported for the Juang. The population did feature a mortality differential, with worse mortality conditions than the Indian national population at this time. Reversed sexual mortality differentials, common in South Asian populations, were also present for the Juang. Computer projection investigation revealed a steadily growing population, in contrast to some Indian tribal groups faced with extinction.     

Comparison of the mortality profiles of Archaic, Middle Woodland, and Middle Mississippian skeletal populations

Mortality profiles were constructed for four American Indian skeletal populations for the purpose of comparing the frequencies of deaths at given ages between and within the populations. An interpretation of the differential mortality frequencies is then possible. Selected for study were the Archaic population from Indian Knoll, Kentucky, an Illinois Archaic series and a Middle Woodland Hopewellian population, both from the Klunk Mounds in southwestern Illinois, and a Middle Mississippian population from Dickson Mounds, Illinois. It was found that in the Archaic populations there were significantly higher percentages of deaths throughout the first three decades than among either the Hopewell or Middle Mississippian populations. Although the mortality profiles of the latter two groups more closely approximated each other, the average age at death was greater for the Hopewellian population. Suggested are different behavioral adjustments to stress. However, with a few notable exceptions, the fluctuations in the frequencies of death follow similar profiles in the mortality curves, indicating that common to all four populations were certain ages at which time death was more likely to occur. Various interpretations are offered to explain these periods of greater mortality.     

Patterns of natural mortality in stream‐living brown trout (Salmo trutta)

1. We tested the hypothesis that lifetime mortality patterns and their corresponding rates and causal factors differ among populations of stream‐living salmonids. To this end, we examined the lifetime mortality patterns of several successive cohorts of two stream‐living brown trout (Salmo trutta) populations in Spain and Denmark. 2. In the southern population, we observed a consistent two‐phase pattern, in which mortality was negligible during the first half of the lifetime and severe during the rest of the lifetime. In contrast, the northern population demonstrated a three‐phase pattern with an earlier phase varying from negligible to severe, followed by a second stage of weak mortality, and lastly by a third life stage of severe mortality. 3. Despite substantial differences in the mortality patterns between the two populations, the combined effect of recruitment (as a proxy of the density‐dependent processes occurring during the lifetime) and mean body mass (as a proxy of growth experienced by individuals in a given cohort) explained c. 89% of the total lifetime mortality rates across cohorts and populations. 4. A comparison with other published data on populations of stream‐living brown trout within its native range highlighted lifetime mortality patterns of one, two, three and four phases, but also suggested that common patterns may occur in populations that experience similar individual growth and population density.     

Insecticide susceptibility status of Aedes aegypti (Diptera: Culicidae) from Townsville

Insecticide susceptibility of a 1995 Townsville Aedes aegypti (L.) population was investigated in the laboratory according to World Health Organization guidelines. Using baseline data from two Townsville populations (1955 and 1989), larval bioassays detected significant increases in susceptibility to synthetic pyrethroids and malathion, and significant reductions in susceptibility to most organophosphates and propoxur. Adult bioassays detected significant resistance to bendiocarb and DDT. Comparison of larval data with the international reference ROCK strain showed substantial resistance to have developed to malathion and fenthion. Further analysis revealed the presence of distinct substrains in the baseline 1989 population, which displayed varying levels of temephos susceptibility. We concluded that susceptibility investigations should assess mosquito populations collected from many sites within an area rather than taking a single population from one site, and that the 1989 Ae. aegypti colony would be unsuitable for use as a susceptible reference population.     

JC virus as a marker of human migration to the Americas

JC virus is a ubiquitous human polyomavirus present in populations worldwide. Seven genotypes differing in DNA sequence by approximately 1-3% characterize three Old World population groups (African, European and Asian) as well as Oceania. It is possible to follow Old World populations into the New World by the JC virus genotypes they carried. The first population to settle in the Americas, the Native Americans, brought with them type 2A from northeast Asia. European settlers arriving after Columbus carried primarily type 1 and type 4. Africans brought by the slave trade carried type 3 and type 6.