The place of Neandertals in the evolution of hominid patterns of growth and development

This study uses the two developmental fields of dental maturation and femoral growth to determine if the pattern of growth and development in Neandertals (archaic Homo sapiens) was intermediate between that of Homo erectus and recent modern humans. Specimens used in the analysis included Neandertals and Upper Palaeolithic early modern Homo sapiens from Europe and individuals from two recent modern human populations. Ontogenetic data for the H. erectus adolescent KNM-WT 15000 and for Gorilla gorilla were included for comparison. Previous reports have indicated that H. erectus demonstrates a pattern of ontogeny characterized by earlier and more rapid linear growth than in modern humans. Results reported here demonstrate that Upper Paleolithic early modern Homo sapiens display a growth trajectory indistinguishable from that of recent modern humans. The pattern of Neandertal ontogeny is not intermediate between the pattern displayed in H. erectus and the derived pattern seen in the modern reference samples and the early modern H. sapiens sample. The Neandertal growth trajectory is consistent with either slow linear growth or advanced dental development.     

Pattern profile analysis of hominid and chimpanzee hand bones

In a study designed to complement morphological research on hominid hand bones, length and width measurements of the thumb, index, and middle rays were obtained from radiographs of modern human hands. These rays are primary in precision-gripping postures and are therefore the ones most relevant for investigating evolutionary changes in fine manipulation. Pattern profile analysis allows individuals or samples to be plotted against a reference sample in standard deviation units, or Z-scores. It provides an indication of how different measurements are from modern human averages, while taking into consideration the degree of variation present within modern human samples. A pattern profile for chimpanzees is clearly distinct from humans but quite similar to that of a bonobo, demonstrating the promise of pattern analysis. Partial pattern profiles of several of the more complete early hominid bones from Hadar, Swartkrans, and Olduvai (O.H. 7) are presented and compared. Hadar bones are long and wide at midshaft relative to articular widths; both body-size effects and functional differences are likely. Thumb distal phalanges from Swartkrans and Olduvai both have relatively small base widths, but they differ in other proportions. Two first metacarpals from Swartkrans show distinct patterns. The profiles of La Ferrassie I and Shanidar IV show the characteristically large Neanderthal distal phalanges. Profiles of Skhūl IV and P?edmost III are alike in some regions with reference to modern North American white males, though they are less similar overall than are those of the two Neanderthals. © 1995 Wiley-Liss, Inc.     

Constitution and By-Laws of the American Association of Physical Anthropologists

From parent populations (N = 50,000) statistically generated, representing different levels of correlation (r) between the age at death and a hypothetical biological indicator (r = 0.8-0.98), reference samples and target demographic samples are randomly drawn. Two iterative techniques, proportional fitting procedure and Bayesian, are used to estimate from the reference samples the age distribution of the targets. Due to the random fluctuations of the pattern of aging, both in the reference and target samples, these techniques converge only in expectation toward the true value of a distribution, but not in practice for any particular realization. Nevertheless, these techniques allow the estimation of the average of an age distribution, even if its shape is unknown. Under the hypothesis that the target sample is drawn from a stationary population, this average represents the life expectancy at 20 years (plus 20 years). Using this mean age at death for the adults and the juvenility index at death (D5-14/D20-ω), a new set of paleodemographic estimators were derived from 40 archaic life tables. For a hypothesized stable population, they give the life expectancy at birth and at 20 years, and the probability of death at 1 and 5 years. © 1996 Wiley-Liss, Inc.     

The Underlying Structure of Adaptation under Strong Selection in 12 Experimental Yeast Populations

The aims of this study were to determine (i) whether adaptation under strong selection occurred through mutations in a narrow target of one or a few nucleotide sites or a broad target of numerous sites and (ii) whether the programs of adaptation previously observed from three experimental populations were unique or shared among populations that underwent parallel evolution. We used archived population samples from a previous study, representing 500 generations of experimental evolution in 12 populations under strong selection, 6 populations in a high-salt environment and 6 populations in a low-glucose environment. Each set of six populations included four with sexual reproduction and two with exclusively asexual reproduction. Populations were sampled as resequenced genomes of 115 individuals and as bulk samples from which frequencies of mutant alleles were estimated. In a high-salt environment, a broad target of 11 mutations within the proton exporter, PMA1, was observed among the six populations, in addition to expansions of the ENA gene cluster. This pattern was shared among populations that underwent parallel evolution. In a low-glucose environment, two programs of adaptation were observed. The originally observed pattern of mutation in MDS3/MKT1 in population M8 was a narrow target of a single nucleotide, unique to this population. Among the other five populations, the three mutations were shared in a broad target, sensing/signaling genes RAS1 and RAS2. RAS1/RAS2 mutations were not observed in the high-salt populations; PMA1 mutations were observed only in a high-salt environment.     

Disruption of historical patterns of isolation by distance in coastal steelhead

When natural populations exchange migrants at a rate proportional to their geographic distance, population genetics theory leads to the expectation of a pattern of isolation-by-distance (IBD), whereby geographic and genetic distance are correlated. However, the presence or absence of such patterns in modern populations may not fully reflect the historical relationships among those populations. Thus, historical samples, collected prior to modern human impacts, can often provide a critical baseline for comparison with modern populations. Steelhead, the anadromous form of rainbow trout, Oncorhynchus mykiss, are native to western North America and are endangered or threatened throughout most of California, near the southern extent of their native range. Population samples of steelhead collected in 1897 and 1909 in Central California rivers provided the opportunity to evaluate the historical genetic composition and population structure of these threatened fish. Here we show that these steelhead populations had a historically strong correlation between genetic and geographic distance that has been virtually erased in modern populations, suggesting that current relationships among modern steelhead populations are no longer reflective of natural migratory pathways. This demonstrates the critical role of migration in maintaining population relationships of threatened species and highlights the importance of natural history museums in providing historical baseline information.     

Excavating past population structures by surname-based sampling: the genetic legacy of the Vikings in northwest England

The genetic structures of past human populations are obscured by recent migrations and expansions and have been observed only indirectly by inference from modern samples. However, the unique link between a heritable cultural marker, the patrilineal surname, and a genetic marker, the Y chromosome, provides a means to target sets of modern individuals that might resemble populations at the time of surname establishment. As a test case, we studied samples from the Wirral Peninsula and West Lancashire, in northwest England. Place-names and archaeology show clear evidence of a past Viking presence, but heavy immigration and population growth since the industrial revolution are likely to have weakened the genetic signal of a 1,000-year-old Scandinavian contribution. Samples ascertained on the basis of 2 generations of residence were compared with independent samples based on known ancestry in the region plus the possession of a surname known from historical records to have been present there in medieval times. The Y-chromosomal haplotypes of these 2 sets of samples are significantly different, and in admixture analyses, the surname-ascertained samples show markedly greater Scandinavian ancestry proportions, supporting the idea that northwest England was once heavily populated by Scandinavian settlers. The method of historical surname-based ascertainment promises to allow investigation of the influence of migration and drift over the last few centuries in changing the population structure of Britain and will have general utility in other regions where surnames are patrilineal and suitable historical records survive.     

现代中国人眼眶的形态变异

研究证实人类骨性[眶形态具有明显的]化变化,在现代人群之间的表现也有一定程度的差别,因而[眶形态是研究人类]化及现代人群关系的重要特征之一。但是,学术界对与眼眶形态有关的许多问题还不是很清楚,或有争议。基于这一情况,本文对3项代表眼眶形态的性状在五组全新世近代—现代人群中的表现情况进行了观测,并结合对比了部分更新世晚期人类化石标本。本文研究发现:在中国地区,人类[眶的高低变异在]化过程中具有明显的时代变化,从新石器时代起出现了区域性的差异,并一直延续到现代;方形眼眶应该是中国人群较稳定的连续性特征,其高出现率从更新世一直延续到现代;在中国人群中,眼眶外下侧缘圆钝这一特征应该也是从更新世一直延续到现代的,但是其高出现率则只维持到新石器时代为止。     

The timing of human adaptation from Neanderthal introgression

Admixture has the potential to facilitate adaptation by providing alleles that are immediately adaptive in a new environment or by simply increasing the long-term reservoir of genetic diversity for future adaptation. A growing number of cases of adaptive introgression are being identified in species across the tree of life, however the timing of selection, and therefore the importance of the different evolutionary roles of admixture, is typically unknown. Here, we investigate the spatio-temporal history of selection favoring Neanderthal-introgressed alleles in modern human populations. Using both ancient and present-day samples of modern humans, we integrate the known demographic history of populations, namely population divergence and migration, with tests for selection. We model how a sweep placed along different branches of an admixture graph acts to modify the variance and covariance in neutral allele frequencies among populations at linked loci. Using a method based on this model of allele frequencies, we study previously identified cases of adaptive Neanderthal introgression. From these, we identify cases in which Neanderthal-introgressed alleles were quickly beneficial and other cases in which they persisted at low frequency for some time. For some of the alleles that persisted at low frequency, we show that selection likely independently favored them later on in geographically separated populations. Our work highlights how admixture with ancient hominins has contributed to modern human adaptation and contextualizes observed levels of Neanderthal ancestry in present-day and ancient samples.     

Mammalian body size changes and Plio-Pleistocene environmental shifts: implications for understanding hominin evolution in eastern and southern Africa

This study examines geographic and temporal variation in three mammalian taxa co-occurring in eastern and southern Africa. The selected taxa-the spotted hyena (Crocuta crocuta), the plains zebra (Equus burchellii), and the impala (Aepyceros melampus)--are geographically widespread in modern times and are abundant in eastern and southern African Plio-Pleistocene fossil sites. Craniodental measurements of modern conspecifics from known geographic locations are compared using multivariate statistical methods to discern patterns of modern geographic variation within taxa. Modern and fossil samples are statistically compared to assess the nature and extent of inferred shifts in body size, both between modern samples and through time in each region. These results indicate that modern spotted hyenas and plains zebras exhibit mainly size variation between regions, with southern African samples possessing statistically larger craniodental metrics than eastern African samples. Comparison of fossil and modern samples reveals that the fossil assemblages do not show the same pattern of geographic variation. Significant temporal changes are more numerous between fossil and modern eastern African samples, and these changes are not mirrored by similar changes in the southern African samples. The changes experienced by taxa in eastern Africa appear to have been more extreme and wide-ranging than those in southern Africa, a presumed refugium. This result accords well with genetic studies of several large mammal species and paleoenvironmental studies suggesting that eastern African localized environments were more affected by tectonism and volcanism than were those in southern Africa. This study suggests that different evolutionary scenarios may have existed within Africa during the Plio-Pleistocene, but that both regions played unique and complementary roles in the evolution of African hominins and the broader faunal community.     

Long‐term changes in the chromosomal inversion polymorphism of Drosophila subobscura. II. European populations*

The chromosomal polymorphism of 13 European populations of Drosophila subobscura has been compared with that of the same populations collected 15–35 years ago. The chromosomal polymorphism of the old populations differs significantly from that of the new populations, mainly for chromosomes U and O. There is a very good agreement between the geographical space and the genetic space as shown by a graphical representation of the 26 statistical populations (13 old and 13 new) obtained by a principal coordinate analysis. This reflects both the existence of significant latitudinal clines for the frequencies of some chromosomal arrangements in the old and new samples and systematic changes that have taken place in these populations during the period that elapsed between the two surveys. An increase in the frequency of those arrangements typical of southern latitudes and a decrease for those common in northern latitudes is observed in all populations – Mediterranean, Atlantic and Central European. Furthermore, the genetic distances of the new populations to a southern population of reference have decreased in comparison with those of the old populations. These changes could be the result of climatic factors that are correlated with latitude. In particular, the assumption that global warming is responsible for all the changes observed appears rather likely. Whether these systematic changes of the chromosomal polymorphism are a consequence of local adaptations or have been produced by migration from the south remains an open question.     

Bone remodeling rates and skeletal maturation in three archaeoloqical skeletal populations

Cortical bone remodeling rates for rib samples from three archaeological populations and a modern autopsy sample were determined using an algorithm developed by Frost. (Frost [1987a] Calcif. Tissue Res. 3:211–237). When plotted against the relative antiquities for population samples, histomorphometric variables; i.e., activation frequency (μ _rc, net bone formation (_netV_f,r,t), and mean annual bone formation rate (V_f,r,t), exhibit a concordant trend of increased cortical bone remodeling activity levels over time. Two intensive foraging populations, Windover and Gibson, are similar for all bone remodeling parameters and have the lowest remodeling activity levels among the samples. The more recent Ledders sample, which is reported to practice agricultural subsistence, is consistently intermediate between these and a modern autopsy sample. Although there appear to be differences in bone formation rates among the populations, it is concluded that these differences cannot be attributed to differences in bone remodeling rates among the populations, but rather are reflecting different effective ages of adult compacta for their ribs. These findings suggest that the earlier populations, particularly Windsor and Gibson, appear to have reached skeletal maturity at an older age than observed for modern. © 1995 Wiley-Liss, Inc.     

PERT: A Method for Expression Deconvolution of Human Blood Samples from Varied Microenvironmental and Developmental Conditions

The cellular composition of heterogeneous samples can be predicted using an expression deconvolution algorithm to decompose their gene expression profiles based on pre-defined, reference gene expression profiles of the constituent populations in these samples. However, the expression profiles of the actual constituent populations are often perturbed from those of the reference profiles due to gene expression changes in cells associated with microenvironmental or developmental effects. Existing deconvolution algorithms do not account for these changes and give incorrect results when benchmarked against those measured by well-established flow cytometry, even after batch correction was applied. We introduce PERT, a new probabilistic expression deconvolution method that detects and accounts for a shared, multiplicative perturbation in the reference profiles when performing expression deconvolution. We applied PERT and three other state-of-the-art expression deconvolution methods to predict cell frequencies within heterogeneous human blood samples that were collected under several conditions (uncultured mono-nucleated and lineage-depleted cells, and culture-derived lineage-depleted cells). Only PERT''s predicted proportions of the constituent populations matched those assigned by flow cytometry. Genes associated with cell cycle processes were highly enriched among those with the largest predicted expression changes between the cultured and uncultured conditions. We anticipate that PERT will be widely applicable to expression deconvolution strategies that use profiles from reference populations that vary from the corresponding constituent populations in cellular state but not cellular phenotypic identity.     

Changes in the sexual dimorphism of the human mandible during the last 1200 years in Central Europe

According to many investigations, changes in mandibular morphology can occur synchronously with changes in the environment, and sexual dimorphism of the mandible can be influenced by the environment. Sexual dimorphism during the last 1200 years was evaluated using geometric morphometric analysis of virtual cranial models. The method of geometric morphometrics allows differences in size and shape to be assessed separately. We analyzed groups of adult individuals dating to Early Middle Ages, High Middle Ages, Early Modern Ages and from a modern Czech population (21st century). Significant sexual dimorphism in mandibular size was found in all populations. A trend in the sexual dimorphism of size was seen, with differences between the sexes increasing gradually over time. Size changes in female mandibles were a better reflection of environmental conditions and climate than size changes in male mandibles. Regarding changes in the sexual dimorphism of shape, significant dimorphism was found in all four samples. However, the pattern of mandibular shape dimorphism was different and varied considerably between samples. There was only one stable shape trait showing sexual dimorphism across all four samples in our study: the gonion lies more laterally in male than in female mandibles and male mandibles are relatively wider than female mandibles. Sexual dimorphism of shape is not influenced by the climate; instead sexual selection might play a role. This research supports earlier studies that have found that the degree and pattern of sexual dimorphism is population-specific and the factors regulating sexual dimorphism today may not be the same as those in the past.     

Within-group human variation in the Asian Pleistocene: the three Upper Cave crania

Numerous studies on Pleistocene samples have shown that within-group cranial variation was greater than that seen today. The three anatomically modern Upper Cave crania (UC 101, UC 102, and UC 103) from Zhoukoudian, China provide one of the best samples available for addressing the issue of the antiquity of the modern pattern of within-group cranial variability because archaeological evidence indicates that they are spatially and temporally restricted. Research on the Upper Cave fossils usually only includes UC 101 and UC 103 because of postmortem damage to UC 102's cranial vault. However, the face of UC 102 is undamaged, allowing for most facial measurements to be performed accurately. In this study we use facial dimensions to compare all three Upper Cave specimens, and we evaluate whether the variation seen among them is larger than that observed in extant populations.Using a worldwide sample of modern populations to establish a baseline, the three Upper Cave crania were compared to each other. Since there is disagreement over the sex of UC 102, this specimen is treated alternately as a female and as a male. Results show that the Upper Cave specimens exhibit significantly more variation than do individuals within more recent human populations, especially if UC 102 is considered male. Furthermore, results indicate that the fossils never fall into the same modern human group, and that each specimen is significantly atypical of its nearest modern neighbor in multivariate space.We conclude that the three Upper Cave crania do not represent a family group but are representative of the larger contemporaneous heterogeneous Asian Pleistocene population. Our results support the contention that today's within-group homogeneity is a relatively recent phenomenon, and is likely the result of a Neolithic population expansion and its many effects.     

Probit analysis of Upper Pleistocene hominids

Probit analysis allows the testing of the normality of a sample population where curve fitting and differential weighting occur simultaneously. Probit analysis may be utilized with small samples, and is ideal for use in the study of fossil populations. It is assumed that population which are normally distributed are likely to be in genetic equilibrium, so that graphic and computational probit analysis may be used to discern the effects of evolutionary forces on human populations. Probit analysis of cranial length in a sequence of Athenian population is presented in order to verify its sensitivity to these evolutionary forces. Probit analysis and other tests of homogeneity are applied to similar variables of Upper Pleistocene European Neandertal and modern man.Despite significant differences between variable means of Neandertal and modern man, probit analyses of their combined populations showed no less deviation from normality than either group separately. This suggests that the evolutionary changes in the cranium from the Neandertal stage to the modern stage of man were effected without significantly disrupting the genetic equilibrium of these populations, i.e. that rapid changes in these populations are unlikely to have occurred.     

Another look at shape variation in the distal femur of Australopithecus afarensis: implications for taxonomic and functional diversity at Hadar

Previous studies have recognized two patterns of distal femoral morphology among the specimens from Hadar (Ethiopia) assigned to Australopithecus afarensis. Size and shape differences between the well-preserved large (AL 333-4) and small (AL 129-1a) distal femora have been used to invoke both taxonomic and functional differences within the A. afarensis hypodigm. Nevertheless, prior studies have not analyzed these specimens in a multivariate context, nor have they compared the pattern of shape differences between the fossils to patterns of sexual dimorphism among extant taxa (i.e., the manner in which males and females differ). This study reexamines morphometric differences between the above specimens in light of observed levels of variation and patterns of sexual dimorphism among extant hominoids. Eight extant reference populations were sampled to provide a standard by which to consider size and shape differences between the fossils. Samples include three populations of modern humans, two subspecies of Pan troglodytes, three subspecies of Gorilla gorilla, Pan paniscus, and Pongo pygmaeus. Using size ratios and scale-free "shape" data (both derived from 2-D coordinate landmarks), size and shape differences between the fossils were evaluated against variation within each reference population using an exact randomization procedure. Growth Difference Matrix Analysis (GDMA) was used to test whether the pattern of morphological differences between the fossils differs significantly from patterns of sexual dimorphism observed among the ten extant groups. Overall morphometric affinities of the fossils to extant taxa were explored using canonical variates analysis (CVA).Results of the randomization tests indicate that the size difference between the Hadar femora can be easily accommodated within most hominoid taxa at the subspecific level (though not within single-sex samples). In addition, the magnitude of shape differences between the fossils can be commonly sampled even within most single-sex samples of a single hominoid subspecies. The pattern of morphological differences between the fossils does not differ statistically from any average pattern of femoral shape dimorphism observed among living hominoids. Moreover, contrary to prior claims, and despite a size disparity between the fossils greater than is typically observed within some chimpanzee and human populations, the two Hadar fossils appear to be much more similar to one another in overall shape than either specimen is to any extant hominoid group.     

Evolution of an invasive rodent on an archipelago as revealed by molar shape analysis: the house mouse in the Canary Islands

Aim The aim of this paper is to identify the patterns in the morphological differentiation in Canary Island mice, based on fossil and modern samples. In order to achieve this, the mouse species present on the archipelago were first compared with a set of continental mice. The differences between the continental and Canary Island samples, and among the Canary Island samples, provide insights into the processes of colonization and the subsequent insular evolution. Location Canary archipelago. Methods An outline analysis based on Fourier transformation was used to quantify shape differences between lower molars. Together with the fossil and modern Canary Island samples, a reference set of genotyped continental populations of the commensal Mus musculus and the wild Mus spretus was used for comparison. Results The morphometric analysis showed that all the mouse specimens from the Canary Islands and Cape Verde belonged to Mus musculus domesticus. Lower molars of extant mice from La Gomera, El Hierro, Gran Canaria, Tenerife, and to a lesser degree from Lanzarote, were similar to those of genotyped M. m. domesticus from the continent, while teeth of extant mice from Fuerteventura were more divergent. Fossil mice from Fuerteventura were very similar to the extant representatives on this island, and similar to the fossil mice on the nearby islands of Lobos and La Graciosa. Main conclusions The mouse present on the Canary archipelago has been identified as the house mouse M. m. domesticus. Based on the shape of the lower molar, the Canary Island mice are divergent from the continental ones, but the degree of divergence varies with the geography of the archipelago. Overall, populations from eastern islands are more divergent from the continental mice than populations from western ones. Fossil populations indicate that this situation was established several centuries ago. Two main factors may have contributed to this pattern: the appearance of different types of environment on the islands since the successful settlement of the mouse, and/or the number of subsequent introductions of continental individuals via shipping.     

Secular changes in craniofacial morphology of the Portuguese using geometric morphometrics

This study examines patterns of secular change in cranial morphology in the New Lisbon collection, a documented skeletal collection from Lisbon, Portugal with birth years from 1806 to 1954. This period represents a time when Lisbon was undergoing increased urbanization and population growth, as well as changes in mortality and fertility patterns. Previous studies from the U.S., Europe, and Japan have reported significant secular changes in cranial morphology over the past 200 years. In the current study, secular changes were analyzed using three-dimensional geometric morphometrics methods. The results from this study demonstrate a significant change in cranial morphology over the roughly 150-year period. Allometry was rejected as a causal factor of this change because there was no association found between temporal change and size. The pattern of temporal change is similar to that observed in other populations in the U.S., Europe, and Japan, including decreased facial breadth and a more inferiorly placed cranial base. This study, along with previous research, suggests a similar pattern of change occurs in genetically and geographically diverse populations experiencing modern environmental conditions. We argue that because the secular changes are focused in the cranial base, a region of the skull that experiences a relatively early growth curve, changes related to declines in childhood morbidity and mortality are likely important factors related to the observed changes.     

Epidemiological approach to the paleopathological diagnosis of leprosy

In paleopathology it is usually assumed that modern diagnostic criteria can be applied to infectious diseases in the past. However, as both the human species and populations of pathogenic microorganisms undergo evolutionary changes, this assumption is not always well-founded. To get valid estimates of the frequency (the point prevalence at death) of leprosy in skeletal samples, sensitivity, specificity, and sample frequency must be estimated simultaneously. It is shown that more than three symptoms must be evaluated in at least three samples in order to reach estimates with well-described properties. The method is applied to three skeletal samples from Medieval Denmark; the samples were scored for the presence of seven osteological conditions indicating leprosy. For the osteological conditions, sensitivity varied from 0.36-0.80, and specificity from 0.58-0.98. The frequency of leprosy in the three samples was: Odense (a lepers' institution), 0.98, 95% CI 0.64-1.00; Malm? (urban cemetery), 0.02, 95% CI 0.00-0.07; and Tirup (rural cemetery), 0.36, 95% CI 0.23-0.46. It is concluded that it is indeed possible to estimate disease frequencies without reference to modern standards, and that leprosy occurred with widely differing frequencies in different segments of the Medieval population in southern Scandinavia.