AAPA 2011 abstracts

A draft of the abstracts from the 80th meeting of the American Association of Physical Anthropologists is online. Some titles of interest:

Cristian Capelli et al.
Early Y chromosome lineages in Africa: the origin and dispersal of Homo sapiens.

The study of Y chromosome variation in extant populations has provided significant insights into the genetic history of Homo sapiens. Focusing on sub-Saharan Africa, demographic events associated with the spread of languages, agriculture and pastoralism have been targeted but little is known on the early history of the continent. The first two branches of the Y chromosome genealogy, namely haplogroup A and B, are African specific, with average continental frequencies of 14-34%, reaching up to 65% in groups of foragers . Despite the potential of such lineages in revealing signatures of the ancient peopling of the continent, an exhaustive investigation of their distribution and variation is currently missing. Here we show that their systematic dissection provides novel insights into the early history of our species. We highlighted complex pattern of populations’ dynamics among hunter-gatherer communities, evidence for the peopling of western and southern Africa, and showed the retention of the very early human Y chromosome lineages in eastern and central but not southern Africa. These results open new perspectives on the early African history of Homo sapiens, with particular attention to areas of the continent where human fossil remains and archaeological data are scanty.

Aslihan Sen et al.

The genetic history of the Karachays:Insights from mtDNA and Y-chromosome evidence

The Karachay-Malkar population of the northwestern Caucasus Mountains has an interesting but unclear history. Oral traditions indicate that they descended from the Alans, ancient Iranian tribes who entered the region starting in the 1st century BC. However, they now speak a Kipchak Turkic language, which was purportedly brought to the Caucasus by the Kumans from the Minusinsk Basin (Yenisei River-Altai Mountains). They are also allegedly related to the Hun-Bulgars, with the name Malkar/Balkar being evidence for this affiliation. Therefore, to elucidate their genetic past, we characterized genetic variation in 106 Karachay individuals using a combination of HVS1/ HVS2 sequencing and SNP analysis for mtDNAs and SNP and STR analysis for Y-chromosomes. We observed a predominance of mtDNA haplogroups H and U in this population, along with a minority of East Eurasian lineages, and mostly Y-chromosome haplogroups G, I, J and R1. The mtDNA data suggest that the Karachay are most similar to the Adygei, among Caucasus populations, and have affinities with eastern Iranians, supporting the hypothesized link to Scythio-Iranians (Alans), although being quite distant to Turkic speaking indigenous Altaians. By contrast, Y-chromosome data point to genetic links with populations from Anatolia, the Near East and the Balkans, as well as the Volga-Ural region, Central Asia and Siberia, the source area for ancient Turkic populations. Using these data and associated genealogical and linguistic evidence, we attempt to reconstruct the history of the Karachay population and assess its genetic relationships to the diverse ethnolinguistic groups of the Caucasus.

Jasem Theyab et al.
The genetic structure of the Kuwaiti population: mitochondrial DNA markers.

In the past few decades, researchers using human mitochondrial DNA (mt- DNA) have significantly contributed to our understanding of human evolution and migration. However, little attention has been paid to the Arabian Peninsula which is assumed to be one of the first inhabited regions following the expansion of early Homo sapiens out of Africa. Recently, a number of investigations have started to reconstruct human expansion through the archaeology and the study of the genetic structure of populations of the Arabian Peninsula. Populations of Kuwait, located in the Northeast portion of the Arabian Peninsula, have not been studied from a molecular genetic perspective. This research investigated the mitochondrial DNA (mtDNA) genetic variation in 117 unrelated individuals to determine the genetic structure of the Kuwaiti population and compared the Kuwaiti population to their neighboring populations. Restriction fragment length polymorphism (RFLP) and mt- DNA sequencing analyses were used to reconstruct the genetic structure of Kuwait. The result showed that the Kuwaiti population has a high frequency of haplogroup pre-HV (18%) and U (12%) similar to other Arabian populations. In addition, the African influence was detected through the presence of haplogroup L (1.6%). Furthermore, the MDS plot showed that the Kuwaiti population is clustered with neighboring populations, including Iran and Saudi Arabia, but not Iraq.

Kristin L. Young et al.
Paternal genetic history of the Basque population of Spain.

This study examines the genetic variation in Basque Y chromosome lineages using data on 12 Y-STR loci in a sample of 158 males from four Basque provinces of Spain. In agreement with previous studies, the Basques are characterized by high frequencies of haplogroup R1b (83%). Five additional haplogroups were identified in this sample: E1b1b (6%), J2a (3%), I2 (3%), G2a (2%), and L (1%). Only 8% of haplotypes were found in more than one province, and the AMOVA analysis shows only a small amount of variation (1.71%, p50.0369) is accounted for between provinces, demonstrating the overall homogeneity of this population. Gene and haplotype diversity levels in the Basques are on the low end of the European distribution (gene diversity: 0.4268; haplotype diversity: 0.9421). Other isolated populations in Europe, including the Swedish Saami, the Roma in Portugal, and Albanians in Kosovo, also exhibit low haplotype diversity levels. Comparison of the Garza-Williamson Index for the Basques and 36 additional European populations shows no significant impact of a recent genetic bottleneck on the continent. A bootstrapped neighbor-joining tree (R2 5 0.922) of Shriver’s genetic distances (DSW) clusters Basque populations with other Atlantic Fringe groups (Galicia, Ireland) and the non- Indo-European Saami. Paleolithic and Neolithic contribution to the paternal Basque gene pool was estimated by measuring the proportion of proposed Paleolithic (R1b, I2a2) and Neolithic haplogroups (E1b1b, G2a, J2a). The Basque provinces show varying degrees of post-Neolithic contribution in the paternal lineages, with 10.9% Neolithic lineages in the combined sample.

Timothy D. Weaver
Did a short-term event in the Middle Pleistocene give rise to modern humans?

It is often stated that modern humans originated 250,000-150,000 years ago. This statement implies, at least implicitly, that something ‘‘special’’ happened at this point in the Middle Pleistocene, such as a speciation event that was perhaps triggered by, or resulted in, a bottleneck in human population size. Two pieces of evidence are usually said to support this contention: that living human mitochondrial DNA haplotypes coalesce _200,000 years ago, and that fossil specimens classified as anatomically modern humans begin to appear shortly afterward. Alternatively, modern human origins could have been a lengthy process that lasted from the divergence of the modern human and Neandertal evolutionary lineages _400,000 years ago to the expansion of modern humans out of Africa _50,000 years ago, and nothing particularly ‘‘special’’ happened 250,000-150,000 years ago. Because this alternative model does not posit a discrete origins event, it may be better able to explain why [50,000-year-old fossils are arguably only ‘‘near modern’’ in anatomy. Here I use computer simulations based on theory from population and quantitative genetics to show that the alternative lengthy-process model also is consistent with a _200,000-year-old mitochondrial DNA coalescence time and the appearance shortly afterward of fossil specimens that, at least for some traits, appear to be anatomically modern. I further discuss how these two models differ in their predictions and whether or not it is possible to distinguish between them with current fossil and genetic evidence.

Steven L. Wang

Regional isolation and extinction? The story of mid-Pleistocene hominins in Asia.

Over the past decade, numerous reviews of the Middle Pleistocene record have taken place in light of new fossil discoveries. However, with primary foci on the Euro- African records, much of the rich fossil evidence in Asia was sidelined and overlooked. It is thus unsurprising that in the minds of many, Asia remains terra incognita— and its hominin record exotic. Moreover, the accuracy of the Asian chronology remains problematic, adding another layer of impediment to our understanding of regional evolution and local adaptation. In this context, I bring a synergistic review of the chronology of mid-Pleistocene hominins from East and South Asia, including recent new dates from key sites such as Zhoukoudian Locality 1 and Hathnora. Using 3-D geometric morphometric data, I examine cranial shape changes between H. erectus and mPH (post-erectus, non- Neandertal mid-Pleistocene Homo), as well as both to later Pleistocene hominins. A large number of not-often-discussed specimens are considered (e.g., Hexian, Nanjing 1, Maba, and Ngawi), many of them original fossils. The cranial anatomy from the Asian mid- Pleistocene suggests the existence of at least two distinctive groups in the region. Additionally, a north-south (geographical) shape difference is observed, hinting the presence of paleodemes each evolving in relative isolation. The shape affinity of mPH to extra-Asian fossils is confirmed; however, depending on the fossil in question (Dali or Narmada), the said affinity to Kabwe and Petralona is exclusive. This, coupled with a limited number of good sample, warrants caution against lumping all Asian mPH within the H. heidelbergensis hypodigm.

John Hawks
Deep genealogy, Neandertal ancestors, and our accelerating evolution

Anthropologists have long confused genealogical and behavioral definitions of humanity. At least five out of six living living humans have Neandertal ancestors, which comprise an estimated 1 to 4% of their ancestry. Human genes have divergent genealogical histories, representing multiple "archaic" populations inside and outside of Africa. Late Pleistocene populations show comparable technical and symbolic abilities within and outside of Africa. A humanlike vocal-auditory channel had appeared before 600,000 years ago. Yet humans of the last 40,000 years have evolved extremely rapidly, in some instances diversifying; in others paralleling each other. Using new visualization methods, I examine the genealogical patterns of human genes. The impact of our rapid Holocene evolution simplifies some genealogical relationships while partially obscuring earlier ones. The genetic echoes of Neandertals and other archaic populations emerge against a slim network binding all living people. These networks show the impact of adaptive potential in ancient human populations. A broad view of human cultural and technical records suggests that gene-culture interaction may be a fundamental aspect of Pleistocene human evolution.