Selected abstracts from 2008 AAPA meeting:
Interaction in pigmentation genes creates variation in brown irises.
E.E. Quillen1, S. Beleza2, E.J. Parra3, R.W. Pereira4, M.D. Shriver1. 1Department of Anthropology, Pennsylvania State University, 2Institute of Molecular Pathology and Immunology, University of Porto, 3Department of Anthropology, University of Toronto, 4Department of Genomics and Biotechnology, Catholic University of Brasília
Iris pigmentation varies substantially in humans and may have been under either natural or sexual selection at different times during our evolutionary history. While less than 10% of the people today have blue eyes, previous analyses have focused on the genetic basis of the differences between blue and brown iris pigmentation or between blue and green as light eyes and brown as dark eyes while neglecting the variation within brown eyes. In a heterogeneous brown-eyed Brazilian population, both iris and skin pigmentation vary widely and are significantly correlated (r2=0.39), suggesting that the same or linked genes are determining these two traits. However, an alternate explanation for this correlation between skin and eye pigmentation is admixture stratification which can lead to similarly high correlations among unlinked markers or traits. The history of tripartite admixture (European, West African, and Indigenous American) investigated using Ancestry Informative Markers, makes Brazil the ideal population to study the interaction between genes related to pigmentation of the eye and skin. Polymorphism previously associated with skin pigmentation differences in the parental populations, including SLC24A5, KITLG, MATP, OCA2, and TYRP1, were investigated to uncover the magnitude of their influence on pigmentation variation in brown irises.
Bringing the Stone Age into the Information Age: introducing the Paleoanthropology Database.
Z.J. Throckmorton. Department of Anthropology, University of Wisconsin, Madison. Online databases and datasets have become indispensable tools for modern scientists.
A number of such databases relevant to paleoanthropology are currently in development; many of these can be accessed through Paleoanthportal.org. These databases are thus far narrow in their scope and detailed in their content. I present here the Paleoanthropology Database (PADB), the first broad and general database designed to be useful to both researchers and students of human evolution. The database contains 40 types of basic data categories filled with information culled from the published literature. These data categories include, for example, age of the site, skeletal elements present, taxonomic affinities, archeological and behavioral evidence, and associated faunal remains, all fully referenced to an extensive source list (over 4,000 references in total for Europe). Here I present the first phase of the database, 300 European sites. An additional 900 African and Asian sites, as well as Miocene hominoid sites, will be added in the future. The primary goal of PADB is the facilitation of access to the evidence of human evolution through its open access status (anyone with a computer that is online may use it). Its secondary goal is to be a continuously updated source of paleoanthropological data through a streamlined updating protocol (utilizing the familiar Excel spreadsheet). At the heart of PADB’s ease of use and updateability are its straightforward database structure (two MySQL tables) and flexible, simple, yet powerful search functions (written largely in Perl). The database can be accessed through Johnhawks.net.
Reconstruction of the Early Neolithic/Bronze Age Population Diversity of the Lake Baikal Region Using mtDNA Polymorphism from Shamanka II Cemetery
H. Vahdati Nasab1, 2, T. A. Thomson1, F. J. Bamforth2, and V. I. Bazaliiski3. 1Department of Anthropology, University of Alberta, 2Human Identification Lab for Archaeology, Department of Laboratory Medicine and Pathology, University of Alberta, 3Department of Archaeology and Ethnography, Irkutsk State University.
This research examines the mtDNA polymorphism among individuals buried at a Neolithic (ca. 5000-4000 BC) hunter-gatherer cemetery, Shamanka II (field season 2002), located on the southwestern tip of Lake Baikal, Siberia. The present study principal research objective aims to compare the mtDNA polymorphism observed at Shamanka II cemetery to the mtDNA results of a previous study (Mooder, 2004), which includes Lokomotiv and Ust’Ida. Like Shamanka II, Lokomotiv is representative of the same culture group (Kitoi) and is contemporaneous in age (5000-4000 BC) while Ust’Ida is representative of a Bronze Age culture group (Serovo-Glazkovo, 1000 BC). There is a pronounced hiatus in radiocarbon dates stretching between the Neolithic and Bronze Age (4900-4200 BC) cultures around Lake Baikal region (Weber, 2002). Mooder’s (2004) results revealed disparate mtDNA distribution between preand post-hiatus groups. Our results indicate although the Neolithic Kitoi (Shamanka II and Lokomotiv) share the identical haplogroups with the Bronze Age Serovo-Glazkovo, the frequency distributions between pre- and post-hiatus cemetery groups are very different. Thus the general model for biological discontinuity between the pre- and post-hiatus Cis-Baikal populations is not disputed.
Metric and non-metric trait variation in the dentition of Holocene Khoesan populations.
W. Black, R.R. Ackermann, J. Sealy. Department of Archaeology, University of Cape Town.
There have been many studies of dental variation in Holocene populations of Europe and the Americas, but few of African populations. Here, we present preliminary work on dental variation in the Khoesan, an African people who have received considerable attention from archaeologists and physical anthropologists. Recent research on well-dated Khoesan skeletal material has revealed general cranial size and stature fluctuations during the past 12,000 years, which appear to result from intrinsic factors affecting the populations, rather than gene flow from outlying areas. These results are consistent with hypotheses of morphological and genetic continuity in Southern African populations during this time. Most previous work has, however, focused on the second half of the Holocene. Here, we add to this body of work by examining dental variation among the Khoesan, extending back into the early Holocene. Metric and non-metric data were collected from >500 adult individuals. When possible, standard dental measurements were taken on all teeth. Cervical measurements, which are less affected by heavy wear, were also taken on all molars. Additionally, dentition was scored for a suite of dental morphological attributes, including 40 crown, root and intraoral osseous traits. Results demonstrate fluctuations in tooth size that generally conform with the mid- to late Holocene size variations observed in cranial and postcranial material. Teeth, during this time period, appear to be smaller than Early Holocene counterparts and discernible reductions are identified through most measurements. Qualitative trait variation is largely consistent throughout sample, supporting the hypothesis of population continuity throughout the Holocene.
Modern European population affinities: a dental study.
S.T. Price. Dept. of Anthropology, New York University, New York Consortium in Evolutionary Primatology (NYCEP).
European population history has been investigated largely through genetics and archaeological research, and has revealed a complex history for this region. Dental morphology is genetically controlled and only marginally influenced by environment. In addition, dental remains are the most common and often best-preserved remains from past populations, and have been shown to be good indicators of biological affinity. For these reasons, dental analyses will add important evidence to debates regarding European population history. Metric and nonmetric data were collected on 160 modern human individuals curated in the Natural History Museum, London and the American Museum of Natural History. Dental morphology was scored according to the Arizona State University Dental Anthropology System (ASUDAS). Statistical analyses including mean measure of divergence indicate important population differences as well as affinities between some groups. The current study is a pilot project as part of a larger investigation into European population history, but preliminary analyses of dental morphology indicate at least one division in Europe. This division seems to correspond to geographic location, and can broadly be categorized as an east-west separation of populations. More eastern populations not only have higher frequencies of certain dental traits, such as shoveling and double shoveling, but also show a tendency toward higher levels of expression of those traits as well. Overall, these analyses indicate different recent population histories for Eastern and Western Europe. Future research will examine more individuals over more time periods to understand this complex history.
Is there a biological rationale to the Frankfurt horizontal plane?
A. Barash, A. Marom. Department of Anatomy and Anthropology, Sackler School of Medicine, Tel Aviv University, Israel
The Frankfurt horizontal plane (FHP) is one of the most frequently used reference planes in morphological sciences, cranial surgery and dental medicine. The biological basis for this plane is that in humans it puts the line of vision parallel to the ground, perpendicular to earth’s gravitational field. Over the years several authors have criticized the use of this plane. While some doubted the spatial stability of the reference points, others claimed that, as intended by its original proponents, the plane should only be used in humans, since most other animals, including non-human primates, do not hold their head in the same manner as humans. The object of this study was to asses the nature of the FHP in human and non-human primates. This was done by defining a new plane, an optic plane (OP), using the orientation of the medial rectus (MR) muscle. The rationale behind this new plane was the assumption that humans and most primates, gaze habitually parallel to the ground, and that the medial recti muscles only rotate the eyes about the vertical axis. Three points- the origin of the left MR and the insertion of the left and right MR where digitized from CT scans. This new plane was compared with the FHP. The results indicate that in humans the two planes are almost parallel, demonstrating that the FHP indeed applies to human studies. Additionally discussed are the nature of the plane in non-human primates and its possible role as cross species plane.
Modern human limb proportions follow Allen’s rule predictions and reflect long term climate adaptations rather than short term epigenetic influences.
R.W. Higgins. Dept. Anthropology, George Washington University.
Distal limb segment length, relative to proximal limb segment length, is found to correlate with climate in modern human populations. The question remains whether this trait is determined by adaptation or epigenetic influences. Experiments on lab animals support the hypothesis that cold temperature influences limb development by reducing growth plate kinetics and/or vascular supply. Reduction in vascular supply would theoretically have a more pronounced effect on the smaller distal limb segments. This study uses a natural experiment, the migration of two modern human populations to North America, to examine the role of natural selection on human limb proportions. The hypotheses to be tested are: (1) If relative distal limb length is largely an inherited trait shaped over long periods of time by natural selection, then the trait should persist several generations after a population enters a new climate and (2) if limb proportions are largely a product of epigenetic influences, then limb proportions should not differ between populations living in the same environment. European American and African American long bones from the Terry Collection were measured (N = 80). Statistical analysis shows that (1) distal segments differed more between populations than did proximal segments with European Americans exhibiting relatively shorter distal segments, and (2) crural (p < .01) and brachial (p < .01) indices differed significantly between the two populations. These results suggest that European and African American limb proportions largely reflect ancestral climate adaptations rather than epigenetic influences.
A phylogenetically controlled analysis of the relationship between temperature and modern human limb length variation.
M. Dembo, A. Cross and M. Collard. Department of Archaeology, Simon Fraser University.
Several studies have found that modern human limb length variation is consistent with Allen’s Rule, which holds that there is a positive correlation between peripheral body part length and temperature in homeothermic species. However, none of these studies has controlled for the phylogenetic relationships among populations. This is potentially problematic because such relationships render taxa nonindependent, and data point independence is a key assumption of correlation analysis. To investigate this issue, anthropometric and temperature data were collected from the literature for indigenous populations from five continents. Next, the impact of mean annual temperature on limb segment length was investigated by analyzing subsamples stratified in such a way as to counter the over representation of warm climate populations in the complete sample. Subsequently, subsamples that returned significant correlations were subjected to phylogenetically controlled correlation analysis in CAIC. CAIC calculates correlation coefficients from “independent contrasts”, which estimate the amount of change in variables since taxa last shared a common ancestor. The phylogenetic trees used in CAIC were generated from published genetic distance data. To produce fully resolved trees, modifications were made to the genetic trees based on the linguistic affiliations of the populations. When the issue of over representation was addressed, only two limb segment lengths were significantly correlated with mean annual temperature: lower arm and foot. Only two of the 10 subsamples for these segments returned statistically significant correlations in CAIC. Thus, the analyses do not support the hypothesis that modern human limb length variation is consistent with Allen’s Rule.
Ecological and life course effects on mid upper arm somatic muscle allocation and skeletal stature among Bangladeshi male migrants to the UK.
K.S. Magid1, F.U. Ahamed2, G.R. Bentley3. 1Department of Anthropology, University College London, UK, 2Department of Anthropology, University of Chittagong, Bangladesh 3Department of Anthropology, Durham University, UK.
Life history theory predicts that selection will favour physiological mechanisms that efficiently regulate the allocation of energy and time between competing functions: reproduction, maintenance, storage and growth. Environmental conditions that lead to increased energetic availability will result in enhanced testosterone levels and anabolic muscle tissue in human males. While apportionment of somatic muscle tissue remains plastic throughout the human male life course, the effects of increased energy availability on muscle allocation are expected to be more pronounced in younger males compared with older males. In our previous study, we demonstrated increased free testosterone among young male migrants from Bangladesh to the UK. In the present study we assess the effects of changes in energetic availability on morphology through measures of mid-upper arm muscle tissue in human males. Anthropometric measures of bone stature (standing height and arm length) and proxies of soft tissue somatic allocation (BMI, midupper arm area, mid upper arm muscle + bone area) were collected on adults aged >40 (n=28) and <40 (n=29) who migrated from Bangladesh to the UK aged 1 to 57 years. A group of sedentee males who have remained in Sylhet, Bangladesh all their lives (n=76) were used as a reference. In line with our hypothesis, our results show that age at migration significantly predicted an increase in mid upper arm muscle tissue for males under the age of 40 years, but was not a significant predictor for males over the age of 40. These findings suggest the allocation of male anabolic muscle tissue is responsive to changes in energetic availability subject to age at migration.
Y-chromosomal evidence of a pastoralist migration through Tanzania to southern Africa.
B.M. Henn1, P.A. Underhill2, A.A. Lin2, P.J. Oefner3, S.A. Tishkoff4, F. Cruciani5, P. Shen6, C. Gignoux1, and J.L. Mountain1,2. Departments of 1Anthropology and 2Genetics, Stanford University, 3Institute of Functional Genomics, University of Regensburg, 4Department of Biology, University of Maryland, 5Dipartmento di Genetica e Biologia Molecolare, Università “La Sapienza”, 6Stanford Genome Technology Center, Stanford University.
The initial origin and mode of diffusion of pastoralism into southern Africa about 2,000 years ago continues to be debated among anthropologists. Were early instances of sheep, pottery and other traits of the pastoralist package transmitted to southerncentral Africa by demic or cultural diffusion? Here we present a novel Y-chromosome specific mutation, E3b1f-M293, which is at high frequencies in pastoralist and huntergatherer groups across eastern and southern Africa, and now links the majority of haplotypes of the previously paraphyletic clade E3b1-M35*. Phylogeographic patterns of the E3b1f frequency distribution and associated microsatellite diversity are consistent with an migration through Tanzania to southern-central Africa. Our Ychromosomal evidence supports a demic diffusion model of pastoralism from eastern to southern Africa, possibly involving a Southern Nilotic-speaking population. The genetic distribution suggests that this dispersal was distinct from the later migration of Bantu-speaking peoples along a similar route. Instead, the expansion time of the E3b1f lineage correlates with archaeological evidence for the arrival of the pastoralist economy in southern Africa about 2,000 years ago.
Geometric Morphometrics Craniofacial Analysis of early Bronze Age Austrian Populations
A. Pellegrini1,2, M. Teschler-Nicola1, P. Mitteröcker2,3, F. Bookstein2,4.1Department of Anthropology, Natural History Museum Vienna, Austria, 2Department of Anthropology, University of Vienna, 3Konrad Lorenz Institute for Evolution & Cognition Research, Altenberg, Austria, 4Department of Psychiatry & Behavioral Sciences, University of Washington, USA.
Archeological data indicate that early Bronze Age populations in lower Austrian do not present a cultural unity, they differ in three regional manifestations: North of the Danube was the area of the Aunjetitz culture, south of the Danube the Unterwölbling (west of Vienna wood) and the Wieselburg culture (east of Vienna wood). In this study the craniofacial morphology of these populations was analyzed with Geometric Morphometrics methods. 58 threedimensional landmarks were measured in 171 adult individuals. We carried out a permutation test MANOVA of the Procrustes coordinates, which yields highly significant differences between the culturally separated populations; moreover a Principal Component Analysis in size-shape space has been carried out, which shows conspicuous differences between the Wieselburg and the Aunjetitz groups, while the (heterogenous) Unterwölblig group overlapps with both of them. A PCA of our sample divided by males and females provided evidence for a more heterogenous cranial morphology in males (length and breath) due to a prolonged cranial growth of males as indicated by an allometric analysis. In contrast, females of the three cultural groups differ in some morphological details (e.g., occipital region) substantiating a partial or total isolation. However, further analysis (e.g., TPS) have been carried out as well, which contribute considerably to our knowledge on mobility and population dynamics in early Bronze Age Austria. As the populations investigated are contemporary, inhabited a small geographic area and share a similar ecological environment, their phenotypic differences will be discussed in terms of genetic differences due to partial or total endogamy.
A comparison of craniofacial secular trends during the 19th and 20th centuries in the U.S. and Portugal.
K.E. Weisensee and R.L. Jantz, Department of Anthropology, University of Tennessee, Knoxville, TN 37996
Craniofacial secular changes over the past two hundred years have been observed in several worldwide populations. This project addresses the question of whether the pattern of change is similar across different populations experiencing the unique 20th century environment. Several studies have documented secular changes in modern populations using anthropometrics on living people, this study, however uses large, welldocumented skeletal samples to compare secular trends across different populations experiencing similar environmental conditions. Both American Black and White populations have been shown to be experiencing a similar pattern of change over time. The Portuguese have also been shown to have experienced significant changes in cranial morphology over the past two hundred years. This study seeks to determine if the pattern of change seen in the American population is the same as that observed in the Portuguese sample from the same time period. Lisbon, Portugal experienced typical changing environmental conditions as in much of the U.S. and Europe whereby urban density increased and mortality patterns were dramatically changed. Unlike the American sample, the Portuguese sample is taken from a single urban population which experienced little immigration. Because of the more tightly controlled Portuguese sample, it is possible to determine if these changes in environmental conditions impacted cranial shape in a similar manner across populations or if the American experience is unique compared to other populations which were not impacted by large immigrate populations. The study uses both interlandmark distances and 3d landmark coordinate data to compare changes between populations from 1820 to 1950.
Detecting natural selection in modern human skulls.
N. Martínez-Abadías1, M. Esparza1, T. Sjøvold2, R. González-José3, M. Santos4, M. Hernández1 and C.P. Klingenberg5. 1Unitat d’Antropologia, Dept. de Biologia Animal, Universitat de Barcelona,2Osteologiska enheten, Stockholms Universitet, 3Centro Nacional Patagónico, Consejo Nacional de Investigaciones Científicas y Técnicas, 4Dept. de Genètica i Microbiologia, Universitat Autònoma de Barcelona, 5Faculty of Life Sciences, University of Manchester.
In human evolution selection is implicitly assumed to be one of the main forces driving evolutionary change and adaptation, but direct evidence of this is rarely available, especially for morphological traits such as skull shape. The main goal of this study is to assess how life-history and fitness measures relate to skull morphological variation, which is the most direct evidence of natural selection. To do this, we use a unique large collection of modern human skulls with genealogical associated data from Hallstatt (Austria). We combine morphological and demographical data and apply multivariate quantitative genetic methods to estimate selection on a three dimensional reconstruction of the skull morphology. Then, we compare the obtained selected pattern with the secular changes observed in this population over a period of almost 200 years. Our results show that selection significantly acted on the evolutionary changes observed in the skull morphology of the Hallstatt’s population during the 18th and the 19th centuries. Indeed, we detect relatively strong directional selection on skull shape and weak stabilizing selection on skull size. However, we find that the expected responses to these selection regimes do not correspond to the actual evolutionary patterns of skull morphology. Therefore, these results emphasize the major role of selective forces both in human skull size and shape, but suggests that microevolutionary factors other than natural selection are also contributing to the evolution of the skull in the Hallstatt’s population and these are obscuring the effects of natural selection.
Chin size and its relationship to facial prognathism in humans.
D. Durand1, D.R. Hunt2. 1Department of Anthropology, The George Washington University, 2Department of Anthropology, Smithsonian Institution.
The presence of a mental eminence has been identified as a trait unique to Homo sapiens. Hypotheses to account for its presence have ranged from a functional adaptation to a byproduct of morphological changes in the skull. The absence of a chin in Homo floresiensis has been used by some scientists to argue that it was not human. Other researchers regard it as a rare trait shared with modern day Australomelanesians, who also lack an apparent chin. In response to this, it has been suggested that there is no such thing as a chinless human, but rather that increased facial prognathism may deemphasize the expression of the chin. The present study tests whether modern humans with greater prognathic faces have smaller chins. Cranial and mandibular measurements were taken from forty-three European- American and African-American individuals and a ratio of facial prognathism to chin size was calculated. Results indicate there is a moderate inverse relationship between chin size and facial prognathism in humans. While these finding do not resolve the debate of adaptation versus a morphological byproduct of change, it appears that the morphological changes producing contraction of the lower face influence an increase in chin size. With this continuum of chin expression in the human species, it is apparent that this trait is not an accurate feature for species identification.
Allelic variability and tests for natural selection at the human ALDH2 locus.: J.C. Long1, C. Lewis4, J. Li1, R. Malhi2, K. Hunley3. 1Dept Human Genetics, Univ Michigan Medical Sch, Ann Arbor, MI; 2Dept Anthropology, University of Illinois, Urbana, IL; 3Dept Anthropology, University of New Mexico, Albuquerque, NM. 4Dept Anthropology, Oklahoma, Norman, OK. This research tests the hypothesis that natural selection has shaped variation at the human ALDH2 gene locus. The enzyme product of this locus catalyzes aldehyde oxidation and is important in alcohol metabolism. ALDH2 shows unusually high allelic differentiation among human populations. A deficiency variant, ALDH2-2, is common in Asians but absent in other populations. This observation implicates the action of natural selection. To test the neutral null hypothesis, we compare the ALDH2-2 allele frequency to the extent of intraallelic variability. We have sequenced 5 kb of DNA flanking the functional ALDH2-2 substitution in a total of 123 people. These people represent sixteen populations, including four indigenous populations from each of four continental regions: Africa, Europe, Asia, and the Americas. We see ALDH2-2 allele only Asians, and not on any other continent. We observe a common background substitution on ALDH2-2. This suggests an old age for ALDH2-2. An old age for the allele is consistent with its high frequency in Asians. However, it is important to examine variability at the locus in the context of the geographic structure of our species. To do this, we established neutral baselines for ALDH2 sequence diversity in our world-wide sample by fitting nested population structure models to the CEPH microsatellite diversity data. In this light, the presence of intraallelic variability and a high allele frequency is inconsistent with the restriction of ALDH2-2 to the Asian continent. Neutral evolution for ALDH2-2 is unlikely.