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Modern Humans. Homo sapiens Origin Theories. Time Line. Homo sapiens (ca. 200 kya…). Fully modern humans Upper Paleolithic tool technology Elaborate Cave Art. Homo sapiens sites in Europe. Transformation. Reduced robusticity-everything gets smaller
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Modern Humans Homo sapiens Origin Theories
Homo sapiens(ca. 200 kya…) • Fully modern humans • Upper Paleolithic tool technology • Elaborate Cave Art
Transformation • Reduced robusticity-everything gets smaller • Back teeth continue to reduce, so do front teeth • Cranial buttresses much less in evidence • loss of brow ridge • development of chin • Sexual dimorphism reduces to modern levels
What causes this overall reduction? • Teeth and cranial buttresses: food processing • Especially cooking technology • Earth ovens • Reduced selection for big molars
What causes this overall reduction? • Skel. robust. & sex. dimorph.: projectiles & string • With modern humans, first projectile weapons • Atlatl (spear-thrower) • No close quarter killing of big-game • Selection reduced for maintaining big bones • Sex. dimorph: males get relatively smaller
Atlatl http://www.crt.state.la.us/archaeology/POVERPOI/food.htm
Multiregional Theory • H. erectus left Africa, spread to other areas of the world, and evolved into modern humans. • Human populations linked throughout the world were linked by gene flow. • Caused modern humans to evolve as a single species from H. erectus to H. sapiens all over the world. • Also separated by distance and environment so had considerable regional variation in morphology. • All genes arose in many parts of the world and were mingled together as people from different regions mated.
Replacement Theory (Eve Hypothesis) • Hominid populations genetically separated during the Middle Pleistocene (before 200,000 B.P.), evolving independently. • Between 100,000 and 200,000 years ago modern humans evolved in Africa and spread out, replacing archaic H. sapiens. • Little or no gene flow as modern humans replaced local populations, all genes necessary for moderns assembled in Africa.
“Mostly” Out of Africa • Modern Humans evolved in Africa around 150,000 years ago. • Spread to Asia, Middle East and Europe and replaced earlier settlers. • In Europe, with Neanderthals, this may have been complicated by absorption of Neanderthals into the Modern gene pool. • This allowed a very few Neanderthal traits to persist in living populations in very small percentages.
Neanderthal/Human Hybrid?? • Analysis of the skeletal remains of this four-year-old boy has revealed that he may be a Neandertal-Cro-Magnon hybrid. • Found in a Portuguese rock-shelter and dating to 25,000 to 24,500 years ago has yielded startling evidence that early modern humans and Neandertals may have interbred. • While the boy's prominent chin, tooth size, and pelvic measurements marked him as a Cro-Magnon, or fully modern human, his stocky body and short legs indicate Neandertal heritage, according to Erik Trinkaus, a paleoanthropologist at Washington University in St. Louis.
Lagar Velho 1 Skeleton Presence of artifacts in burial also a modern trait.
Chin-on Lagar Velho Specimen, not on Neanderthals Lagar Velho 1
Evidence: Fossils • Evidence from Europe and Middle East is inconsistent with Multiregional model. • long period of overlap between Neanderthal and moderns in this area. • anatomically modern people appeared 60,000 years before Neanderthals disappeared.
Evidence: Archaeological • Cave sites in Israel, most notably Qafzeh and Skhul date to nearly 100,000 years and contain skeletons of anatomically modern humans. Qafzeh Cave
Amud and Kebara The presence of Neanderthals at two other caves in Israel, Amud and Kebara, dated to roughly 55,000 years means that Neanderthals and Homo sapiens overlapped in this region for at least 45,000 years. Therefore, if Homo sapiens were in this region for some 45,000 years prior to the disappearance of the Neanderthals, there is no reason to assume that Neanderthals evolved into modern humans.
Evidence: Tools/Culture • Tools associated with moderns are not found with Neanderthals. • A remarkable diversity in stone tool types for moderns. • tool types showed significant change over time and space • artifacts were regularly fashioned out of bone, antler and ivory, in addition to stone • stone artifacts were made primarily on blades and were easily classified into discrete categories, presumably reflecting specialized use
Tools/Culture con’d Burials were accompanied by ritual or ceremony and contained a rich diversity of grave goods Living structures and well-designed fireplaces were constructed Raw materials such as flint and shells were traded over some distances
Genetic Evidence • Contemporary patterns of genetic variation provide clues to origins of modern humans • Mitochondrial DNA (mtDNA) passed from mother to her children, an exact copy of genetic material. • Humans are less genetically variable than other populations-suggests population explosion.
Genetic Evidence, con’d The high degree of similarity between human populations stands in strong contrast to the condition seen in our closest living relatives, the chimpanzees. In fact, there is significantly more genetic variation between two individual chimpanzees drawn from the same population than there is between two humans drawn randomly from a single population.
Genetic Evidence • In support of an African origin for Homo sapiens the work of Cann and Wilson has demonstrated that the highest level of genetic variation in mtDNA occurs in African populations. • This implies that Homo sapiens arose first in Africa and has therefore had a longer period of time to accumulate genetic diversity. • Using the genetic distance between African populations and others as a measure of time, Homo sapiens arose between 100,000 and 200,000 years ago in Africa.
Genetic Evidence • The low amount of genetic variation in modern human populations suggests that our origins may reflect a relatively small founding population for Homo sapiens. • Analysis of mtDNA by Rogers and Harpending supports the view that a small population of Homo sapiens, numbering perhaps only 10,000 to 50,000 people, left Africa somewhere between 100,000 and 200,000 years ago.
Neanderthal mtDNA • Scientists recently succeeded in extracting DNA from several Neanderthal skeletons. • After careful analysis of particularly the mtDNA, but now also some nuclear DNA, it is apparent that Neanderthal DNA is very distinct from our own. • In assessing the degree of difference between DNA in Neanderthals and modern humans, the authors suggest that these two lineages have been separated for more than 400,000 years.
Implications • Suggestions from mtDNA • Human populations spread out across the globe well before any major population expansion took place. • Size of pop before expansion was between 10 and 50,000 people. • Major expansion of people beginning around 100,000-200,000 years ago in Africa and 50,000 years ago in the rest of the world.
Why important? • Resolution of this controversy because it affects our view of contemporary human variation. • Affects our perspective about the significance of genetic differences and modern human populations. • If replacement model correct, then all humans descended from a lineage that arose around 100,000-200,000 years ago. • If multiregional correct then humans related as long as 1 million years ago and arose separately from there.
