A Current Controversy in Human Evolution. Overview

With this issue, the editors of the American Anthropologist publish the second Contemporary Issues Forum, "A Current Controversy in Human Evolution." We find it incumbent upon the flagship journal of the profession to encourage productive discussion of issues of relevance to anthropologists and to the public. With this in mind the editors have targeted broadly significant and controversial topics as foci for the forums with a view to encouraging dialogue. The second forum opens an arena for debate in this journal regarding contemporary theories of modern human evolution and their evidential bases in genetics and the fossil record. We recognize the disputed nature of these issues and the potential importance of such controversies to the profession. Commentary on the forum papers from the readership of the American Anthropologist is welcomed.     

Comparaison de l'expression de certains caractères crâniens sur les hominidés chinois du Pléistocène récent et de l'Holocène (grotte supérieure de Zhoukoudian, sites de Longxian et de Yanqing)

The human remains recovered from “Grotte supérieure de Zhoukoudian” are the best-preserved Late Pleistocene human fossils in East Asia. For decades, as the representative of the Late Pleistocene human in East Asia, the Upper Cave skulls have been playing important role in the research of origins of modern Mongoloids and American Indians. With the advance of the origin and evolution of modern humans, more attention has been paid to the details and the mechanisms for the late Pleistocene human evolution and the formation of modern human populations. Both the origin and diversification of modern humans have been stressed. Some studies further trigger the debaters on the Upper Cave Man concerning its evolutionary level and its role in the formation of modern human populations in East Asia. To further explore these problems, we examined and compared 12 non-metric features on the 3 Late Pleistocene Upper Cave skulls and 162 Holocene individuals earthed from two archaeological sites of North China (Longxian and Yanqing). Our results indicate that 8 on the 12 features have different expression patterns between Upper Cave Man and recent Chinese leading the authors to believe that more primitive expressions appeared on the Upper Cave Man than on recent Chinese populations. Based on these findings, some problems on the intragroup variation in Late Pleistocene and Holocene populations are discussed.     

African human diversity, origins and migrations

The continent of Africa is thought to be the site of origin of all modern humans and is the more recent origin of millions of African Americans. Although Africa has the highest levels of human genetic diversity both within and between populations, it is under-represented in studies of human genetics. Recent advances have been made in understanding the origins of modern humans within Africa, the rate of adaptations due to positive selection, the routes taken in the first migrations of modern humans out of Africa, and the degree of admixture with archaic populations. Africa is also in dire need of effective medical interventions, and studies of genetic variation in Africans will shed light on the genetic basis of diseases and resistance to infectious diseases. Thus, we have tremendous potential to learn about human variation and evolutionary history and to positively impact human health care from studies of genetic diversity in Africa.     

山顶洞人与现代华北人头骨非测量性特征比较及中国更新世晚期人类演化的一些问题

山顶洞人化石是迄今在东亚地区发现的数量最为丰富、保存状态最为完好的更新世晚期人类化石。多年来,山顶洞人作为东亚地区更新世晚期人类的代表,在研究东亚地区现代蒙古人种及美洲印第安人起源方面发挥着重要作用。随着对现代人起源与演化研究的深入,学术界对更新世晚期人类演化及现代人群形成过程的许多细节及演化机制予以了越来越多的注意,提出了现代人群出现时间及现代人群分化时间的概念。一些研究对山顶洞人的演化程度及其在东亚地区现代人群形成上的作用也提出了不同看法。为了深入探讨这些问题,本文对12项颅骨非测量特征在山顶洞人与现代中国人的表现情况进行了对比研究。发现有8项特征在山顶洞人与现代中国人之间具有不同的表现,作者认为山顶洞人在颅骨特征表现上较现代中国人具有更多的原始性。在此基础上,作者就更新世晚期人群内部变异、现代人群特征标准等问题进行了讨论。     

Did farming arise from a misapplication of social intelligence?

The origins of farming is the defining event of human history--the one turning point that has resulted in modern humans having a quite different type of lifestyle and cognition to all other animals and past types of humans. With the economic basis provided by farming, human individuals and societies have developed types of material culture that greatly augment powers of memory and computation, extending the human mental capacity far beyond that which the brain alone can provide. Archaeologists have long debated and discussed why people began living in settled communities and became dependent on cultivated plants and animals, which soon evolved into domesticated forms. One of the most intriguing explanations was proposed more than 20 years ago not by an archaeologist but by a psychologist: Nicholas Humphrey suggested that farming arose from the 'misapplication of social intelligence'. I explore this idea in relation to recent discoveries and archaeological interpretations in the Near East, arguing that social intelligence has indeed played a key role in the origin of farming and hence the emergence of the modern world.     

Quantitative trait loci and the study of plant domestication

Plant domestication ranks as one of the most important developments in human history, giving human populations the potential to harness unprecedented quantities of the earths resources. But domestication has also played a more subtle historical role as the foundation of the modern study of evolution and adaptation. Until recently, however, researchers interested in domestication were limited to studying phenotypic changes or the genetics of simple Mendelian traits, when often the characters of most interest – fruit size, yield, height, flowering time, etc. – are quantitative in nature. The goals of this paper are to review some of the recent work on the quantitative genetics of plant domestication, identify some of the common trends found in this literature, and offer some novel interpretations of the data that is currently available.     

Les origines de l’art et les théories sur l’évolution humaine : le cas français

In recent years, we have witnessed an international debate about the question of the origins of art. On the one hand, some specialists have suggested that art appeared for the first time at the beginning of the Upper Paleolithic associated to the emergence of Homo sapiens sapiens. From this point of view, Paleolithic art as well as other hallmarks of behavioral modernity were exclusive to anatomically modern humans. On the other hand, some scholars have put into question the traditional paradigm concerning the origins of art and have suggested that artistic objects arose over a long period of time among different species, including Neanderthals. In order to contextualize this debate, we analyze in this article the history of the different interpretations and controversies concerning the question of the origins of art. Taking as reference the French case, we examine the connections between the different theories about art's origins suggested by Pleistocene art specialists during the last century and the dominant paradigms in human paleontology during the same period. Informed by one another, the question of the origins of art and that of human evolution seems to be inextricable linked.     

Genomics refutes an exclusively African origin of humans

Ten years ago, evidence from genetics gave strong support to the "recent African origin" view of the evolution of modern humans, which posits that Homo sapiens arose as a new species in Africa and subsequently spread, leading to the extinction of other archaic human species. Subsequent data from the nuclear genome not only fail to support this model, they do not support any simple model of human demographic history. In this paper, we study a process in which the modern human phenotype originates in Africa and then advances across the world by local demic diffusion, hybridization, and natural selection. While the multiregional model of human origins posits a number of independent single locus selective sweeps, and the "out of Africa" model posits a sweep of a new species, we study the intermediate case of a phenotypic sweep. Numerical simulations of this process replicate many of the seemingly contradictory features of the genetic data, and suggest that as much as 80% of nuclear loci have assimilated genetic material from non-African archaic humans.     

Forensic Anthropology and Bioarchaeology in the American Anthropologist Rare but Exquisite Gems

This article explores forensic anthropological and bioarchaeological publishing patterns in the American Anthropologist (n.s.). Early contributions by Harris Hawthorne Wilder on both subjects are considered in detail, including previously unrecognized discussions of taphonomic variables. Articles on forensic anthropology in the American Anthropologist appear only during the first four decades of publication. While relatively well represented in early issues, bioarchaeological articles decrease in number over time. Comparative data from six other journals suggest that their presence has had a profound effect on the American Anthropologist . The impact of the "new" physical anthropology on publishing patterns in bioarchaeology is also assessed. [Keywords: forensic anthropology, funerary archaeology, paleodemography, paleopathology, taphonomy]     

基于DNA分子的现代人起源研究35年回顾与展望

1983年,有学者首次发表现代人线粒体DNA进化树,认为现代人可能起源自亚洲。1987年,又有学者按照分子钟假说得到线粒体在10-20万年前出自非洲的推论。随后,以分子钟为前提的Y染色体和常染色体DNA研究也支持了出非洲的结论,该结论逐渐成为分子进化领域的主流理论。2010年,对尼安德特人常染色体基因组的研究指出其对现代人有遗传贡献,这颠覆了人们先前关于现代人只来源自非洲,其他大洲的当地古人被完全取代的认知。目前,单地区起源说已经被修正为同化说。尽管学界对非洲人遗传多样性最高这一现象有共识,但是对该现象的不同解读却可以得出两种迥然不同的结果,现代人出亚洲说和出非洲说。大量研究证实基因组的大部分序列是有功能的,并处在遗传变异水平的饱和态,这质疑了中性理论以及由它推导的现代人出非洲说的合理性,而中性理论的提出恰恰是用来解释并非普遍存在的分子钟的。近年来已经有研究者从新理论的角度解读遗传多样性的饱和态和线性态,人们对现代人起源的认识将会进一步加深完善。     

DNA and recent human evolution

The study of recent human evolution, or the origin of modern humans, is currently dominated by two theories. The recent African origin hypothesis holds that there was a single origin of modern humans in Africa about 100,000 years ago, after which these humans dispersed throughout the rest of the world, mixing little or not at all with nonmodern populations. The multiregional evolution hypothesis holds that there was no single origin of modern humans but, instead, that the mutations and other traits that led to modern humans were spread in concert throughout the old world by gene flow, leading to genetic continuity among old world populations during the past million years. Although both of these theories are based on observations stemming from the fossil record, much discussion and controversy during the past six years has focused on the application and interpretation of studies of DNA variation, particularly mitochondrial DNA (mtDNA). The past year, especially, has brought new data, interpretations, and controversies. Indeed, I initially resisted writing this review, on the grounds that new information would be likely to render it obsolete by the time it was published. However, now that the dust is starting to settle, it seems timely to review various investigations and interpretations and where they are likely to lead. While the focus of this review is the mtDNA story, brief mention is made of studies of nuclear DNA variation (both autosomal and Y-chromosome DNA) and the implications of the genetic data with regard to the fossil record and our understanding of recent human evolution.     

Deep divergences of human gene trees and models of human origins

Two competing hypotheses are at the forefront of the debate on modern human origins. In the first scenario, known as the recent Out-of-Africa hypothesis, modern humans arose in Africa about 100,000-200,000 years ago and spread throughout the world by replacing the local archaic human populations. By contrast, the second hypothesis posits substantial gene flow between archaic and emerging modern humans. In the last two decades, the young time estimates--between 100,000 and 200,000 years--of the most recent common ancestors for the mitochondrion and the Y chromosome provided evidence in favor of a recent African origin of modern humans. However, the presence of very old lineages for autosomal and X-linked genes has often been claimed to be incompatible with a simple, single origin of modern humans. Through the analysis of a public DNA sequence database, we find, similar to previous estimates, that the common ancestors of autosomal and X-linked genes are indeed very old, living, on average, respectively, 1,500,000 and 1,000,000 years ago. However, contrary to previous conclusions, we find that these deep gene genealogies are consistent with the Out-of-Africa scenario provided that the ancestral effective population size was approximately 14,000 individuals. We show that an ancient bottleneck in the Middle Pleistocene, possibly arising from an ancestral structured population, can reconcile the contradictory findings from the mitochondrion on the one hand, with the autosomes and the X chromosome on the other hand.     

Contested Pasts and the Practice of Anthropology

With this issue, the editors of the American Anthropologist introduce the first Contemporary Issues Forum, "Contested Pasts and the Practice of Anthropology." We find it incumbent upon the flagship journal of the profession to encourage productive discussion of current issues of relevance to anthropologists and the public. The editors have targeted broadly significant and controversial topics as foci for the forums with a view to encouraging productive dialogue. With this initial forum we open an arena for debate regarding anthropological practice and discourse and their consequences in the contemporary period of ethnic resurgence and (neo)colonial disempowerment. We recognize the debated nature of these issues and the potential importance of such controversies to the profession. Commentary on the forum papers from the readership of the American Anthropologist is welcome.     

Paleoamerican morphology in the context of European and East Asian late Pleistocene variation: implications for human dispersion into the New World

Early American crania show a different morphological pattern from the one shared by late Native Americans. Although the origin of the diachronic morphological diversity seen on the continents is still debated, the distinct morphology of early Americans is well documented and widely dispersed. This morphology has been described extensively for South America, where larger samples are available. Here we test the hypotheses that the morphology of Early Americans results from retention of the morphological pattern of Late Pleistocene modern humans and that the occupation of the New World precedes the morphological differentiation that gave rise to recent Eurasian and American morphology. We compare Early American samples with European Upper Paleolithic skulls, the East Asian Zhoukoudian Upper Cave specimens and a series of 20 modern human reference crania. Canonical Analysis and Minimum Spanning Tree were used to assess the morphological affinities among the series, while Mantel and Dow-Cheverud tests based on Mahalanobis Squared Distances were used to test different evolutionary scenarios. Our results show strong morphological affinities among the early series irrespective of geographical origin, which together with the matrix analyses results favor the scenario of a late morphological differentiation of modern humans. We conclude that the geographic differentiation of modern human morphology is a late phenomenon that occurred after the initial settlement of the Americas.     

古人类对赭石的利用行为在其演化中的意义

长期以来赭石利用行为被视为人类行为现代性的标志之一,受到国内外考古学界的普遍关注。本文回溯和梳理了全球背景下赭石利用的起源、发展及其与人类演化史的关系。在现代人广泛分布于全球之后,赭石利用行为更加丰富和多样化地出现在各地,然而现有考古证据表明该行为并不是解剖学意义上的现代人突变性的发明。赭石利用不能被单纯地定义为现代人行为,而应是有着长久演化积累的现代性行为之一。在长期传播与演化过程中,赭石的功能从意识形态、艺术表达等逐渐扩展到作为矿物成分被用于实际生产生活。赭石的利用历史可追溯到中更新世中期,但其广泛分布仍与晚更新世以来现代人的广泛扩散直接相关,对于理解现代人的意识形态、社会组织方式以及艺术表达、精神文化发展都具有重要的意义。国内目前所发表的相关考古学证据相对较少,以下马碑遗址为代表的材料,也恰处于现代人在全球广泛扩散的窗口期,并伴有进步的细小石器镶嵌使用的证据,成为认识东亚现代人行为的关键性考古证据。     

现代人出现和演化的化石证据

近年来,新材料的发现、新测年结果的更新以及分子生物学的加入,刷新了关于现代人在各主要区域出现时间、在迁徙扩散中与古老人群的交流模式、晚更新世晚期现代人演化复杂场景等方面的认识。本文梳理了关于现代人出现和演化路径的主要化石证据和研究成果。目前化石证据显示：非洲准现代人的出现时间最早可到MIS 9阶段,非洲现代人在中更新世晚期到晚更新世化石证据连续;欧亚大陆现代人的出现时间可追溯到MIS 6阶段,在MIS 5a-MIS 4阶段经历“瓶颈期”,在MIS 3阶段开始广泛分布。从已有证据来看,MIS 3和MIS 2阶段,欧亚大陆不同区域的现代人演化链条并非单一线性,而是呈现有断点的“网状”演化模式。     

Multiple dispersals and modern human origins

Despite a massive endeavour, the problem of modern human origins not only remains unresolved, but is usually reduced to “Out of Africa” versus multiregional evolution. Not all would agree, but evidence for a single recent origin is accumulating. Here, we want to go beyond this debate and explore within the “Out of Africa” framework an issue that has not been fully addressed: the mechanism by which modern human diversity has developed. We believe there is no clear rubicon of modern Homo sapiens, and that multiple dispersals occurred from a morphologically variable population in Africa. Pre-existing African diversity is thus crucial to the way human diversity developed outside Africa. The pattern of diversity—behavioural, linguistic, morphological and genetic—can be interpreted as the result of dispersals, colonisation, differentiation and subsequent dispersals overlaid on former population ranges. The first dispersals would have originated in Africa from where two different geographical routes were possible, one through Ethiopia/Arabia towards South Asia, and one through North Africa/Middle East towards Eurasia.     

尼安德特人基因组学研究进展

尼安德特人是现代人最近的旁支,也是化石资料最丰富的古人类。在现代人起源问题的争论中,尼安德特人对现代人是否有遗传贡献是一个焦点问题。文章综述了近年来关于尼安德特人线粒体基因组和核基因组的研究进展,初步研究表明尼安德特人可能对现代人有遗传贡献,这引发了人们对现代人起源问题的重新思考。藉尼人基因组研究经验进行的古人类基因组学研究将有望揭开现代人起源的谜团,并丰富进化生物学相关领域的理论体系。     

Genetic evidence and the modern human origins debate

A continued debate in anthropology concerns the evolutionary origin of 'anatomically modern humans' (Homo sapiens sapiens). Different models have been proposed to examine the related questions of (1) where and when anatomically modern humans first appeared and (2) the genetic and evolutionary relationship between modern humans and earlier human populations. Genetic data have been increasingly used to address these questions. Genetic data on living human populations have been used to reconstruct the evolutionary history of the human species by considering how global patterns of human variation could be produced given different evolutionary scenarios. Of particular interest are gene trees that reconstruct the time and place of the most recent common ancestor of humanity for a given haplotype and the analysis of regional differences in genetic diversity. Ancient DNA has also allowed a direct assessment of genetic variation in European Neandertals. Together with the fossil record, genetic data provide insight into the origin of modern humans. The evidence points to an African origin of modern humans dating back to 200,000 years followed by later expansions of moderns out of Africa across the Old World. What is less clear is what happened when these early modern humans met preexisting 'archaic human' populations outside of Africa. At present, it is difficult to distinguish between a model of total genetic replacement and a model that includes some degree of genetic mixture.     

Theoretical framework of population genetics with somatic mutations taken into account: application to copy number variations in humans

Traditionally, population genetics focuses on the dynamics of frequencies of alleles acquired by mutations on germ-lines, because only such mutations are heritable. Typical genotyping experiments, however, use DNA from some somatic tissues such as blood, which harbors somatic mutations at the current generation in addition to germ-line mutations accumulated since the most recent common ancestor of the sample. This common practice may sometimes cause erroneous interpretations of polymorphism data, unless we properly understand the role of somatic mutations in population genetics. We here introduce a very basic theoretical framework of population genetics with somatic mutations taken into account. It is easy to imagine that somatic mutations at the current generation simply add individual-specific variations, as errors in mutation detection do. Our theory quantifies this increment under various conditions. We find that the major contribution of somatic mutations plus errors is to very rare variants, particularly to singletons. The relative contribution is markedly large when mutations are deleterious. Because negative selection also increases rare variants, it is important to distinguish the roles of these mutually confounding factors when we interpret the data, even after correcting for demography. We apply this theory to human copy number variations (CNVs), for which the composite effect of somatic mutations and errors may not be negligible. Using genome-wide CNV data, we demonstrate how the joint action of the two factors, selection and somatic mutations plus errors, shapes the observed pattern of polymorphism.