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Chapter 12

Textbook Chapter 12 Notes

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University of Toronto Mississauga
Heather Miller

Notes From Reading CHAPTER 12:T HE ORIGIN ANDD ISPERSAL OM ODERN H UMANS (279-306) Learning Objectives  Describe the time frame and geographic locations for the earliest evidence of odern humans in Africa as well as elsewhere in the Old World  Compare the different models accounting for the origin and dispersal of modern humans and evaluate how fossil and genetic evidence support these models  Explain from the archaeological evidence how and why modern human behavior in the Upper Paleolithic differed from that of their Middle Paleolithic predecessors Introduction  Probably close to 200,000 ya, the first modern Homo sapiens populations appeared in Africa  150,000 years or so, their descendant had spread across most of the Old World, even expanding as far as Australia  African populations of H. heidelbergensis are the most likely ancestors of the earliest modern H. sapiens  The Upper Paleolithic period begins in western Europe around 40,000 ya and ends roughly 10,000 ya  By 12,000-10,000 ya, the technology of Upper Paleolithic hunter-gatherers was a diverse and effective as that of historically documented hunter-gatherers Approaches to Understanding Modern Human Origins  The regional continuity model and various versions of replacement models are the two models that attempt to organize and explain modern human origins The Regional Continuity Model: Multiregional Evolution  Suggest that local populations (not all) in Europe, Asia and Africa continued their indigenous evolutionary development from premodern Middle Pleistocene forms to anatomically modern humans  People question: how could anatomically modern humans arise separately in different continents and end up so much alike, both physically and genetically?  This multiregional model answers this question by: o Denying that the earliest modern H. sapien populations originated exclusively in Africa o Asserting that significant levels of gene flow (migration) between various geographically desired premodern populations were extremely likely throughout the Pleistocene  Advocates of the multiregional model recognize that a strong influence of modern humans evolving first in Africa Replacement Models  Replacement models all emphasize that modern humans first evolved in Africa and only later dispersed to other parts of the world  Two versions of such replacement models have been proposed o The first emphasizing complete replacement  The complete replacement model proposes that anatomically modern populations arose in Africa within the last 200,000 years, then migrated from Africa, replacing populations in Europe and Asia o This model doesn’t account for a transition from premodern forms to modern H. sapiens anywhere in the world except Africa  Migrating African modern H. sapiens could not have interbred with local non-African populations, because the African modern humans were a biologically different species  Most molecular data come from contemporary species, since DNA is not usually preserved in long-dead individuals  We can conclude that some interbreeding took place between Neandertals and modern humans, arguing against complete replacement and supporting some form of partial replacement Partial Replacement Models  New findings from DNA analysis further confirm that the degree of interbreeding was modest, ranging from 1 to 4 percent in modern populations outside Africa  Contemporary Africans have no trace of Neandertal genes, suggesting that any interbreeding occurred after modern humans migrated out of Africa  Tentative conclusion from these preliminary findings suggests that the interbreeding occurred soon after modern humans emigrated out of Africa  In tropical areas, DNA degrades rapidly; so it seems a long shot that any usable DNA can be obtained from hominins that lived in many extremely large and significant regions Notes From Reading CHAPTER 12:T HE ORIGIN ANDDISPERSAL OFM ODERN HUMANS (279-306) The Earliest Discoveries of Modern Humans Africa  In Africa, several early fossils have been interpreted as fully anatomically modern forms  It is very likely that early modern humans appeared in East Africa by shortly after 200,000 ya and had migrated to southern Africa by approximately 100,000 ya  Herto o Fossils are helping to resolve key issues regarding modern human origins o Herto fossils/remains were between 160,000 and 154,000 ya, making these the best-dated hominin fossils from this time period from anywhere in the world o The mostly complete adult cranium is very large, with an extremely long cranial vault o The overall impression is that this individual is clearly Homo sapiens – o To distinguish these individuals from fully modern humans (H. sapiens sapiens), the researchers have placed them in a newly defined subspecies: Homo sapiens idaltu o Idaltu means “elder” The Near East  In Israel, researchers found early modern H. sapiens fossils  Such early dates for modern specimens pose some problems for those advocating the influence of local evolution, as proposed by the multiregional model  This chronological overlap in such a small area is the reason anthropologists have suggested this region as a likely place where Neandertals and modern humans might have interbred Asia  Fossils from the Chinese sites – Upper Cave at Zhoukoudian, Tianyuan Cave (very near Zhoukoudian), and Ordos, in Mongolia – are all fully modern, from Late Pleistocene  At the Tianuan Cave, important finds consisting of a fragmentary skull, a few teeth, and several postcranial bones, this fossil is accurately dated by radiocarbon at close to 40,000 ya o Skull shows mostly modern features, but has a few archaic characteristicsit as well Australia  During glacial times, the Indonesian islands were jointed to the Asian mainland, but Australia wasn’t  Bamboo rafts may have been used to cross the ocean between islands, and this would certainly have been dangerous and difficult  Human occupation of Australia appears to have occurred quite early, with some archeological sites dating to 55,000 ya  Fossils from a site called Kow Swamp suggest that people who lived there between about 14,000 and 9,000 ya were different from the more gracile early Australian forms  Fossils display certain archaic cranial traits – receding foreheads, heavy supraorbital tori, and thick bones  Genetic evidence indicates that all native Australians are descendants of a single migration dating back to about 50,000 ya Central Europe  Central Europe has been a source of many fossil fins, including the earliest anatomically modern H. sapiens yet discovered anywhere in Europe  It is clear that by 28,000 ya, modern humans were widely dispersed in central and western Europe Western Europe  Theories of human evolution were based almost exclusively on the western European material  Western Europe has yielded many anatomically modern human fossils, but by far the best-known sample of western European H. sapiens is from the Cro-Magnon site, a rock-shelter in southern France  The Cro-Magnon materials are associated with an Aurignacian tool assemblage, an Upper Paleolithic industry o Aurignacian – pertaining to an Upper Paleolithic stone tool industry in Europe beginning about 40,000 ya  Most of the genetic evidence argue against continuous local evolution producing modern groups directly from any Eurasian premodern population  With all the latest evidence, theres no longer much debate that a large genetic contribution from migrating early modern Africans influenced other groups throughout the Old World  Portugal provides some of the best skeletal evidence of possible interbreeding between Neandertals and anatomically modern H. sapiens  Genetic evidence is unequivocal: Neandertals and modern humans did interbreed at some point Notes From Reading CHAPTER 12:T HE ORIGIN ANDD ISPERSAL OM ODERN H UMANS (279-306) Something New and Different the “Little People”  By 25, 00
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