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What is the out of africa thesis

  1. It is significant that modern anatomy evolved prior to modern behavior. Around 30, years ago humans were anatomically and behaviorally similar throughout the world.
  2. This southern coastal dispersion would have occurred before the dispersion through the Levant approximately 45, years ago. The Upper Paleolithic lifestyle, as it was called, was based essentially on hunting and gathering.
  3. This is theoretically unlikely since Neanderthal traits would have been genetically swamped by the Homo sapiens genes over such a protracted period of time.

Lucy is estimated to have lived 3. Cleveland Natural History Museum, photo by Andrew. Around 30, years ago humans were anatomically and behaviorally similar throughout the world. One of the most hotly debated issues in paleoanthropology the study of human origins focuses on the origins of modern humans, Homo sapiens.

However, by 30, years ago this taxonomic diversity vanished and humans everywhere had evolved into the anatomically and behaviorally modern form. The nature of this transformation is the focus of great deliberation between two schools of thought: Understanding the issue Multiregional theory: The Multiregional Continuity Model15 contends that after Homo erectus left Africa and dispersed into other portions of the Old World, regional populations slowly evolved into modern humans.

Origins of Modern Humans: Multiregional or Out of Africa?

This model contains the following components: Critical to this model are the following tenets: Out of Africa theory: The replacement hypothesis suggests that the genes in fully modern humans all came out of Africa. As these peoples migrated they replaced all other human populations with little or no interbreeding. To understand this controversy, the anatomical, archaeological, and genetic evidence needs to be evaluated. Anatomical evidence Sometime prior to 1 million years ago early hominids, sometimes referred to as Homo ergaster, exited Africa and dispersed into other parts of the Old World.

Living in disparate geographical areas their morphology became diversified through the processes of genetic drift and natural selection. In Europe and western Asia they evolved into the Neanderthals. Neanderthals lived in quasi isolation in Europe during a long, relatively cool period that even included glaciations. Neanderthals are distinguished by a unique set of anatomical features, including: This is a classic example of geographic isolation leading to a speciation event.

In contrast, at roughly the same time, in Africa, a body plan essentially like our own had appeared. While these early Homo sapiens were anatomically modern they were not behaviorally modern.

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It is significant that modern anatomy evolved prior to modern behavior. These early sapiens were characterized by: Archaeological evidence Very interestingly, while Neanderthals and early Homo sapiens were distinguished from one another by a suite of obvious anatomical features, archaeologically they were very similar. This was an abrupt and dramatic change in subsistence patterns, tools and symbolic expression. The stunning change in cultural adaptation was not merely a quantitative one, but one that represented a significant departure from all earlier human behavior, reflecting a major qualitative transformation.

The appearance of fully modern behavior apparently occurred in Africa earlier than anywhere else in the Old World, but spread very quickly, due to population movements into other geographical regions. The Upper Paleolithic lifestyle, as it was called, was based essentially on hunting and gathering. So successful was this cultural adaptation that until roughly 11, years ago, hominids worldwide were subsisting essentially as hunter-gatherers. It was characterized by significant innovation: Precisely how this transformation occurred is not well understood, but it apparently was restricted to Homo sapiens and did not occur in Neanderthals.

Origins of Modern Humans: Multiregional or Out of Africa?

Some archaeologists invoke a behavioral explanation for the change. For example, Soffer11 suggests that changes in social relations, such as development of the nuclear family, played a key role in bringing about the transformation. Klein7, on the other hand, proffers the notion that it was probably a biological change brought about by mutations that played the key role in the emergence of behaviorally modern humans. His biologically based explanation implies that a major neural reorganization of the brain resulted in a significant enhancement in the manner in which the brain processed information.

Origins of Modern Humans: Multiregional or Out of Africa?

This is a difficult hypothesis to test since brains do not fossilize. But it is significant that no changes are seen in the shape of the skulls between earlier and later Homo sapiens. For many anthropologists this represents the final evolutionary leap to full modernity. Shortly after fully modern humans entered Europe, roughly 40, years ago, the Neanderthals began a fairly rapid decline, culminating in their disappearance roughly 30, years ago.

Neanderthals were apparently no match for the technologically advanced fully modern humans who invaded Europe and evidence for interbreeding of these two types of hominids is equivocal.

Origins of Modern Humans: Multiregional or Out of Africa?

What is the out of africa thesis evidence Investigation of the patterns of genetic variation in modern human populations supports the view that the origin of Homo sapiens is the result of a recent event that is consistent with the Out of Africa Model. Studies of contemporary DNA, especially mitochondrial DNA mtDNA which occurs only in the cellular organelles called mitochondria, reveal that humans are astonishingly homogeneous, with relatively little genetic variation.

Furthermore, genetic variation between populations of chimpanzees is enormously greater than differences between European, Asian and African human populations. Africans display higher genetic variation than other populations, supporting the idea that they were the first modern humans. In support of an African origin for Homo sapiens the work of Cann and Wilson1 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, they furthermore suggested that Homo sapiens arose betweenandyears ago in Africa.

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 Harpending12 supports the view that a small population of Homo sapiens, numbering perhaps only 10, to 50, people, left Africa somewhere between 50, andyears ago.

Scientists recently succeeded in extracting DNA from several Neanderthal skeletons. 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 thanyears.

Although in its infancy, such genetic studies support the view that Neanderthals did not interbreed with Homo sapiens who migrated into Europe. It is, therefore, highly likely that modern humans do not carry Neanderthal genes in their DNA. Additional considerations The chronology in the Middle East does not support the Multiregional Model where Neanderthals and anatomically modern humans overlapped for a long period of time.

Cave sites in Israel, most notably Qafzeh and Skhul date to nearlyyears and contain skeletons of anatomically modern humans. Furthermore, Neanderthal remains are known from sites such as the ,year-old Tabun cave, which predates the earliest Homo sapiens by about 10, years in the region. Neanderthals and modern humans coexisted in some parts of the world for thousands of years. The presence of Neanderthals at two other caves in Israel, Amud and Kebara, dated to roughly 55, years means that Neanderthals and Homo sapiens overlapped in this region for at least 55, years.

Therefore, if Homo sapiens were in this region for some 55, years prior to the disappearance of the Neanderthals, there is no reason to assume that Neanderthals evolved into modern humans. Archaeological evidence from Europe suggests that Neanderthals may have survived in the Iberian Peninsula until perhaps as recently as 30, to 35, years ago.

Fully modern humans first appear in Europe at around 35, years ago, bringing with them an Upper Paleolithic tool tradition referred to as the Aurignacian.

  1. Archaeological evidence from Europe suggests that Neanderthals may have survived in the Iberian Peninsula until perhaps as recently as 30, to 35, years ago.
  2. However, by 30, years ago this taxonomic diversity vanished and humans everywhere had evolved into the anatomically and behaviorally modern form.
  3. The presence of Neanderthals at two other caves in Israel, Amud and Kebara, dated to roughly 55, years means that Neanderthals and Homo sapiens overlapped in this region for at least 55, years.
  4. Archaeological evidence from Europe suggests that Neanderthals may have survived in the Iberian Peninsula until perhaps as recently as 30, to 35, years ago.
  5. The stunning change in cultural adaptation was not merely a quantitative one, but one that represented a significant departure from all earlier human behavior, reflecting a major qualitative transformation. The appearance of fully modern behavior apparently occurred in Africa earlier than anywhere else in the Old World, but spread very quickly, due to population movements into other geographical regions.

Hence, Neanderthals and fully modern humans may have overlapped for as much as 10, years in Europe. Again, with fully modern humans on the scene, it is not necessary to have Neanderthals evolve into modern humans, further bolstering the view that humans replaced Neanderthals.

Neanderthals probably did not breed with modern humans but they borrowed some of their tools and skills The situation in southern France is, however, not quite as clear.

The lack of anatomical intermediates at these sites, suggests that if Neanderthals did encounter and borrow some technology from Homo sapiens, they did not interbreed.

For example, if we look at hybrids of lions and tigers they do not possess the head of one species and the body of the other, but exhibit a morphological mixture of the two species. Secondly, and more importantly, acceptance of this specimen as a hybrid would suggest what is the out of africa thesis Neanderthal traits had been retained for some 6, to 10, years after Neanderthals went extinct, which is highly unlikely.

This is theoretically unlikely since Neanderthal traits would have been genetically swamped by the Homo sapiens genes over such a protracted period of time. Proponents of the Multiregional Model, such as Milford Wolpoff, cite evidence in Asia of regional continuity. They see an evolutionary link between ancient Homo erectus in Java right through to Australian aborigines. A possible problem with this view is that recent dating of late surviving Homo erectus in Indonesia suggests that they survived here until 50, years ago, which is potentially when fully modern humans may have arrived in the region from Africa.

China may contain the best evidence for supporting the Multiregional Model.

  • Klein7, on the other hand, proffers the notion that it was probably a biological change brought about by mutations that played the key role in the emergence of behaviorally modern humans;
  • The nature of this transformation is the focus of great deliberation between two schools of thought;
  • Better geological dating and more complete specimens are needed to more fully assess this possibility;
  • Klein7, on the other hand, proffers the notion that it was probably a biological change brought about by mutations that played the key role in the emergence of behaviorally modern humans.

Here there are discoveries of a couple of skulls dated to roughlyyears ago that seem to possess a mixture of classic Homo erectus and Homo sapiens traits.

Better geological dating and more complete specimens are needed to more fully assess this possibility. Conclusion For the moment, the majority of anatomical, archaeological and genetic evidence gives credence to the view that fully modern humans are a relatively recent evolutionary phenomenon. The current best explanation for the beginning of modern humans is the Out of Africa Model that postulates a single, African origin for Homo sapiens. The major neurological and cultural innovations that characterized the appearance of fully modern humans has proven to be remarkably successful, culminating in our dominance of the planet at the expense of all earlier hominid populations.

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