Past is Prologue
Pluvials, droughts, the Mongol Empire, and modern Mongolia
Neil Pederson et al.
Proceedings of the National Academy of Sciences, 25 March 2014, Pages 4375-4379
Abstract:
Although many studies have associated the demise of complex societies with deteriorating climate, few have investigated the connection between an ameliorating environment, surplus resources, energy, and the rise of empires. The 13th-century Mongol Empire was the largest contiguous land empire in world history. Although drought has been proposed as one factor that spurred these conquests, no high-resolution moisture data are available during the rapid development of the Mongol Empire. Here we present a 1,112-y tree-ring reconstruction of warm-season water balance derived from Siberian pine (Pinus sibirica) trees in central Mongolia. Our reconstruction accounts for 56% of the variability in the regional water balance and is significantly correlated with steppe productivity across central Mongolia. In combination with a gridded temperature reconstruction, our results indicate that the regional climate during the conquests of Chinggis Khan's (Genghis Khan's) 13th-century Mongol Empire was warm and persistently wet. This period, characterized by 15 consecutive years of above-average moisture in central Mongolia and coinciding with the rise of Chinggis Khan, is unprecedented over the last 1,112 y. We propose that these climate conditions promoted high grassland productivity and favored the formation of Mongol political and military power. Tree-ring and meteorological data also suggest that the early 21st-century drought in central Mongolia was the hottest drought in the last 1,112 y, consistent with projections of warming over Inner Asia. Future warming may overwhelm increases in precipitation leading to similar heat droughts, with potentially severe consequences for modern Mongolia.
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Laura Betzig
Human Nature, March 2014, Pages 80-99
Abstract:
For more than 100,000 years, H. sapiens lived as foragers, in small family groups with low reproductive variance. A minority of men were able to father children by two or three women; and a majority of men and women were able to breed. But after the origin of farming around 10,000 years ago, reproductive variance increased. In civilizations which began in Mesopotamia, Egypt, India, and China, and then moved on to Greece and Rome, kings collected thousands of women, whose children were supported and guarded by thousands of eunuchs. Just a few hundred years ago, that trend reversed. Obligate sterility ended, and reproductive variance declined. For H. sapiens, as for other organisms, eusociality seems to be an effect of ecological constraints. Civilizations rose up in lake and river valleys, hemmed in by mountains and deserts. Egalitarianism became an option after empty habitats opened up.
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Hugo Reyes-Centeno et al.
Proceedings of the National Academy of Sciences, forthcoming
Abstract:
Despite broad consensus on Africa as the main place of origin for anatomically modern humans, their dispersal pattern out of the continent continues to be intensely debated. In extant human populations, the observation of decreasing genetic and phenotypic diversity at increasing distances from sub-Saharan Africa has been interpreted as evidence for a single dispersal, accompanied by a series of founder effects. In such a scenario, modern human genetic and phenotypic variation was primarily generated through successive population bottlenecks and drift during a rapid worldwide expansion out of Africa in the Late Pleistocene. However, recent genetic studies, as well as accumulating archaeological and paleoanthropological evidence, challenge this parsimonious model. They suggest instead a "southern route" dispersal into Asia as early as the late Middle Pleistocene, followed by a separate dispersal into northern Eurasia. Here we test these competing out-of-Africa scenarios by modeling hypothetical geographical migration routes and assessing their correlation with neutral population differentiation, as measured by genetic polymorphisms and cranial shape variables of modern human populations from Africa and Asia. We show that both lines of evidence support a multiple-dispersals model in which Australo-Melanesian populations are relatively isolated descendants of an early dispersal, whereas other Asian populations are descended from, or highly admixed with, members of a subsequent migration event.
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Neandertal Demise: An Archaeological Analysis of the Modern Human Superiority Complex
Paola Villa & Wil Roebroeks
PLoS ONE, April 2014
Abstract:
Neandertals are the best-studied of all extinct hominins, with a rich fossil record sampling hundreds of individuals, roughly dating from between 350,000 and 40,000 years ago. Their distinct fossil remains have been retrieved from Portugal in the west to the Altai area in central Asia in the east and from below the waters of the North Sea in the north to a series of caves in Israel in the south. Having thrived in Eurasia for more than 300,000 years, Neandertals vanished from the record around 40,000 years ago, when modern humans entered Europe. Modern humans are usually seen as superior in a wide range of domains, including weaponry and subsistence strategies, which would have led to the demise of Neandertals. This systematic review of the archaeological records of Neandertals and their modern human contemporaries finds no support for such interpretations, as the Neandertal archaeological record is not different enough to explain the demise in terms of inferiority in archaeologically visible domains. Instead, current genetic data suggest that complex processes of interbreeding and assimilation may have been responsible for the disappearance of the specific Neandertal morphology from the fossil record.
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Late Pleistocene Human Skeleton and mtDNA Link Paleoamericans and Modern Native Americans
James Chatters et al.
Science, 16 May 2014, Pages 750-754
Abstract:
Because of differences in craniofacial morphology and dentition between the earliest American skeletons and modern Native Americans, separate origins have been postulated for them, despite genetic evidence to the contrary. We describe a near-complete human skeleton with an intact cranium and preserved DNA found with extinct fauna in a submerged cave on Mexico's Yucatan Peninsula. This skeleton dates to between 13,000 and 12,000 calendar years ago and has Paleoamerican craniofacial characteristics and a Beringian-derived mitochondrial DNA (mtDNA) haplogroup (D1). Thus, the differences between Paleoamericans and Native Americans probably resulted from in situ evolution rather than separate ancestry.
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Marrying kin in small-scale societies
Robert Walker & Drew Bailey
American Journal of Human Biology, May/June 2014, Pages 384-388
Objectives: Marriages among kin have the dual effect of both increasing average group relatedness as well as reducing the total number of kin by eliminating more genealogically and geographically distant individuals from kinship networks. Marriage decisions therefore face a tradeoff between density of kin, or formation of intensive kinship systems, and the diversity of kin, or extensive kinship systems. This article tests the hypothesis that extensive kinship systems best characterize hunter-gatherer societies, whereas more intensive forms of subsistence, like horticultural, agricultural, and pastoral economies, are more likely to have intensive kinship systems.
Methods: Here, we investigate the wide range of variation in prevalence of kin marriages across a sample of 46 small-scale societies, split evenly between hunter-gatherers and agropastoralists (including horticulturalists), using genealogies that range in depth from 4 to 16 generations. Regression methods examine how subsistence and polygyny relate to spousal relatedness and inbreeding across societies.
Results: On average, hunter-gatherers show limited numbers of kin marriages and low levels of inbreeding, whereas some agropastoralists are characterized by much higher levels of both, especially in societies where polygynous marriages are more common.
Conclusion: Intensive kinship systems emerge in some intensive economies. This pattern may have favored a kin-selected increase in more large-scale cooperation and inequality occurring relatively recently in human history after the advent of domesticated plants and animals.
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Micro-Biomechanics of the Kebara 2 Hyoid and Its Implications for Speech in Neanderthals
Ruggero D'Anastasio et al.
PLoS ONE, December 2013
Abstract:
The description of a Neanderthal hyoid from Kebara Cave (Israel) in 1989 fuelled scientific debate on the evolution of speech and complex language. Gross anatomy of the Kebara 2 hyoid differs little from that of modern humans. However, whether Homo neanderthalensis could use speech or complex language remains controversial. Similarity in overall shape does not necessarily demonstrate that the Kebara 2 hyoid was used in the same way as that of Homo sapiens. The mechanical performance of whole bones is partly controlled by internal trabecular geometries, regulated by bone-remodelling in response to the forces applied. Here we show that the Neanderthal and modern human hyoids also present very similar internal architectures and micro-biomechanical behaviours. Our study incorporates detailed analysis of histology, meticulous reconstruction of musculature, and computational biomechanical analysis with models incorporating internal micro-geometry. Because internal architecture reflects the loadings to which a bone is routinely subjected, our findings are consistent with a capacity for speech in the Neanderthals.
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The Cradle of Thought: Growth, Learning, Play and Attachment in Neanderthal Children
Penny Spikins et al.
Oxford Journal of Archaeology, May 2014, Pages 111-134
Abstract:
Childhood is a core stage in development, essential in the acquisition of social, practical and cultural skills. However, this area receives limited attention in archaeological debate, especially in early prehistory. We here consider Neanderthal childhood, exploring the experience of Neanderthal children using biological, cultural and social evidence. We conclude that Neanderthal childhood experience was subtly different from that of their modern human counterparts, orientated around a greater focus on social relationships within their group. Neanderthal children, as reflected in the burial record, may have played a particularly significant role in their society, especially in the domain of symbolic expression. A consideration of childhood informs broader debates surrounding the subtle differences between Neanderthals and modern humans.
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Linguistic Phylogenies Support Back-Migration from Beringia to Asia
Mark Sicoli & Gary Holton
PLoS ONE, March 2014
Abstract:
Recent arguments connecting Na-Dene languages of North America with Yeniseian languages of Siberia have been used to assert proof for the origin of Native Americans in central or western Asia. We apply phylogenetic methods to test support for this hypothesis against an alternative hypothesis that Yeniseian represents a back-migration to Asia from a Beringian ancestral population. We coded a linguistic dataset of typological features and used neighbor-joining network algorithms and Bayesian model comparison based on Bayes factors to test the fit between the data and the linguistic phylogenies modeling two dispersal hypotheses. Our results support that a Dene-Yeniseian connection more likely represents radiation out of Beringia with back-migration into central Asia than a migration from central or western Asia to North America.
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Early agriculture and crop transmission among Bronze Age mobile pastoralists of Central Eurasia
Robert Spengler et al.
Proceedings of the Royal Society: Biological Sciences, 22 May 2014
Abstract:
Archaeological research in Central Eurasia is exposing unprecedented scales of trans-regional interaction and technology transfer between East Asia and southwest Asia deep into the prehistoric past. This article presents a new archaeobotanical analysis from pastoralist campsites in the mountain and desert regions of Central Eurasia that documents the oldest known evidence for domesticated grains and farming among seasonally mobile herders. Carbonized grains from the sites of Tasbas and Begash illustrate the first transmission of southwest Asian and East Asian domesticated grains into the mountains of Inner Asia in the early third millennium BC. By the middle second millennium BC, seasonal camps in the mountains and deserts illustrate that Eurasian herders incorporated the cultivation of millet, wheat, barley and legumes into their subsistence strategy. These findings push back the chronology for domesticated plant use among Central Eurasian pastoralists by approximately 2000 years. Given the geography, chronology and seed morphology of these data, we argue that mobile pastoralists were key agents in the spread of crop repertoires and the transformation of agricultural economies across Asia from the third to the second millennium BC.
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A forager-herder trade-off, from broad-spectrum hunting to sheep management at Aşıklı Höyük, Turkey
Mary Stiner et al.
Proceedings of the National Academy of Sciences, forthcoming
Abstract:
Aşıklı Höyük is the earliest known preceramic Neolithic mound site in Central Anatolia. The oldest Levels, 4 and 5, spanning 8,200 to approximately 9,000 cal B.C., associate with round-house architecture and arguably represent the birth of the Pre-Pottery Neolithic in the region. Results from upper Level 4, reported here, indicate a broad meat diet that consisted of diverse wild ungulate and small animal species. The meat diet shifted gradually over just a few centuries to an exceptional emphasis on caprines (mainly sheep). Age-sex distributions of the caprines in upper Level 4 indicate selective manipulation by humans by or before 8,200 cal B.C. Primary dung accumulations between the structures demonstrate that ruminants were held captive inside the settlement at this time. Taken together, the zooarchaeological and geoarchaeological evidence demonstrate an emergent process of caprine management that was highly experimental in nature and oriented to quick returns. Stabling was one of the early mechanisms of caprine population isolation, a precondition to domestication.
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Reconstructing the DNA Methylation Maps of the Neandertal and the Denisovan
David Gokhman et al.
Science, 2 May 2014, Pages 523-527
Abstract:
Ancient DNA sequencing has recently provided high-coverage archaic human genomes. However, the evolution of epigenetic regulation along the human lineage remains largely unexplored. We reconstructed the full DNA methylation maps of the Neandertal and the Denisovan by harnessing the natural degradation processes of methylated and unmethylated cytosines. Comparing these ancient methylation maps to those of present-day humans, we identified ~2000 differentially methylated regions (DMRs). Particularly, we found substantial methylation changes in the HOXD cluster that may explain anatomical differences between archaic and present-day humans. Additionally, we found that DMRs are significantly more likely to be associated with diseases. This study provides insight into the epigenetic landscape of our closest evolutionary relatives and opens a window to explore the epigenomes of extinct species.