The origin of modern humans is one of the most widely debated concerns in the area of paleoanthropology. Ever since the discovery of the Neanderthal in the mid 1800’s, scientists such as Charles Darwin and many others have been overly curious about the similarity of man to certain great apes and how over long periods of time have evolved from different archaic forms of humans up to today’s homo sapiens.
There are two major theories that encompass how modern humans may have evolved from the various groups of hominids that existed in the Old World. These two theories are the Multiregional origin theory and the “Out of Africa” origin theory. I will first introduce the background and logic behind the two theories, and then I will argue, with supporting genetic evidence, why the “Out of Africa” theory is currently the most widely accepted in the field.
The Multiregional hypothesis was originally proposed in 1984 by Milford H. Wolpoff, Alan Thorne and Xinzhi Wu. The theory indicates that the worldwide expansion of modern humans arose from a series of regionally distinct phases of human evolution that physically replaced Old World humans over thousands of years (Wolpoff et al. 1984). According to the theory, about half of the Homo erectus that originated in Africa split up and migrated out to Europe, Asia and Australia. These regional populations slowly, over time, evolved into different forms of archaic humans separately and then eventually evolved into regionally diverse modern humans. The Multiregional theory was once the favored hypothesis for the origin of modern humans. Supporters of the hypothesis have argued that human traits show continuity over time. They argue that early modern humans show some traits consistent with a ...
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...iation in modern human populations suggests that our origins may reflect a relatively small founding population for Homo sapiens. Analysis of mtDNA (Rogers and Harpending 1992) supports the view that a small population of Homo sapiens, numbering perhaps only 10,000 to 50,000 people, left Africa somewhere between 50,000 and 100,000 years ago. There is another similarity between human populations standing 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. Furthermore, genetic variation between populations of chimpanzees is enormously greater than differences between European, Asian and African human populations (Cavalli-Sforza, 2000).
Over the last few hundred years, more and more has been added to the world’s fossil collection, fossils from all over the world. New theories have been created and old theories have almost been proven about the evolution of man. For example, we have proof that different species of man existed with certain types of DNA sequences and instincts, some we may not have anymore, or some that other species did not have back then. Even though it is subjected to much debate, one of the most widely accepted theories however, is that Homo sapiens interbred with the slightly more primitive species of man, the Neanderthal.
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In recent years, the Homo Neanderthalensis were viewed as “subhuman brutes”, but are now seen as a different species from our own (Balter 2001). The Neanderthals were a branch of the Homo genus that evolved in Eurasia at least 200,000 years ago (Fagan 2010). The first Neand...
...he replacement modelers might argue, the examples given for the multi-regional model are isolated freaks. This claim, too, however, is easily disproved by examples of transitionals from outside Africa for which large fossil sample populations exist, as in the case of the Solo River and Arago Cave examples detailed earlier. What becomes clear in the process of examining the many-and-varied fossil examples of transitions between modern and archaic features is that human evolution was more of a tangled, convoluted web than it is the neatly pruned tree that many textbooks are so fond of depicting in illustration. Not all of those specimens detailed here could be the ancestors of modern humans...their odd mixture of features is testament enough to that. But that human evolution was an unfocused, even chaotic process seems less-and-less an overstatement, the more evidence is reviewed. The definition of what are commonly referred to as “modern'; and “archaic'; features may be the results finally of no more than luck of the evolutionary draw, as it were.
According to National Geographic, scientists have sequenced the genome factor of the chimpanzee and found that humans are 98.5% similar to the ape species. The chimpanzee is our closest relative in the animal kingdom; however, some people are not aware of our resembling traits with chimpanzees. Jane Goodall’s, In the Shadow of Man, describes some similar traits humans and chimpanzees have such as their facial expressions and emotions, use of tools, and diet.
Humans know or understand the theory of evolution and how they evolved from apes, but there is always talk of a missing link between apes and modern humans. Apes did not just suddenly evolve into modern day humans. Apes evolved into another species that fall into the relation of modern humans. This is what the missing link is referring to; we call the species hominins. Hominins comprised of many species actually, including but not limited to, Australopithecus afarensis and Homo erectus. Homo erectus may have been a direct descendant of modern Homo sapiens. These species hold strong evidence that they are the missing link between apes and modern humans. There are many pieces of evidence that lay the path of evolution from these species to modern humans, “…these include anatomy, living primate behavior, and genetic relationships” (Stanford, 237). Australopithecus afarensis comes first, existing about 3.9 to 2.9 million years ago, with intermediate anatomical traits between living apes and modern humans; their fossils were found in Africa (Yukimoto). About a million to two million years later, the species Homo erectus came into existence and lots of evidence has been found about this particular species, in fact, it was probable that it was the first species to leave Africa (Yukimoto). These species are significant in the evolution of modern humans. We do not have a clear path or even understand why these species emerged when they did or how they, in theory, eventually evolved into modern humans. We can only assume these things, by using various evolutionary processes such as natural selection, genetic bottleneck, and many more.
The Neanderthals are an extinct species of human that lived in ice age Europe between 120,000-35,000 years ago. This species is known for their receding forehead and prominent brow ridges. We know this species as the uncivilized or unintelligent person or group. Neanderthals are often portrayed as “unintelligent cavemen in animal-skin clothing.” Scientists’ first thought the Neanderthals’ were subhuman, but that thought is beginning to change. The original name given to the Neanderthals when they were first discovered was ‘Homo Neanderthalensis’ and they were considered to be an ancestor to modern humans. “Forty-four years after this biased classification, Neanderthals were reclassified as a human subspecies Homo sapiens Neanderthalensis and
From the ancient bones of the Neanderthals, scientists have been able to extract small amounts of DNA. The DNA comparisons to modern humans show no relationship, implying evolutionary separation (Kunzig, 159). Some anthropologists say the small sections of DNA found are not conclusive evidence, because modern humans show just as much variation in DNA. These people point out that individuals such as the “Portugal Kid” are hybrids of Neanderthals and modern humans, showing there was gene trading. One argument against this is that there is no skull from the ‘Portugal Kid” so it is hard to compare it to Neanderthals. Also, it is known that closely related species can breed and their offspring can be fertile, but they are still separate species (Kunzig, 161).
Neanderthals and modern humans coexisted for well over 100,000 years. Then suddenly Homo neandertalensis began to die out and surrender the earth to Homo sapiens. Paleontologists and anthropologists have entertained several possibilities to the causes of this event: interbreeding among Neanderthals and humans, competition for natural resources, and Darwin’s theory of “survival of the fittest.” What the real cause has been has plagued scientists for years. Now, due to an international research team from Germany, those possibilities have been even further deduced, making it easier to pinpoint the exact reason Homo neandertalensis became extinct.
“The scientific study of how humans developed did not begin until the 1800s in Europe. Until that time, people relied on religious explanations of how humans came into existence. Starting in the 1500s a scientific revolution began to sweep Europe. Thinkers started using scientific methods and experiments to try to better understand the world and the creatures living in it. Eventually these methods were turned to the question of human origins” (The Nature Of Human Origins, 1). Earth made it possible for species to change over time because Ancient Earth provides ability to plenty of time.The Homo Sapien a is very complex creature. The species started off very simple by living in caves and surviving with little food and then later evolved into a species that were able to do many more complex things. The first species was Sahelanthropus tchadensis They were one of the most simple humans in that time period and on. They had very small skulls compared to Homo Sapiens today and their motor skills were just the same. We have evolved and changed for the better both mentally and physically. The Evolution of Homo Sapiens started off simple, such as the Neanderthals, and now we are the most advanced species to ever walk the planet so far.
According to the “out of africa” model, “modern humans evolved relatively recently in Africa, migrated into Eurasia and replaced all populations which had descended from Homo erectus” (Stringer). Human’s
Because of the fault lines that created the Eastern African Rift Valley and its affects on climate and food source availability, the australopithecines that came before early hominins were obligated to adjust from quadripedal to bipedal, increase their brain size and develop greater jaw muscles in order to withstand such extreme environmental pressures (Feder, 2013) (Gani and Gani, 2008) (Maslin et al., 2008) (Ungar and Sponheimer, 2011) (Lewin and Foley, 2004). Rapid and frequent fluctuations in climate (variation selection hypothesis) is most likely the major pressure that required early human ancestors to modify from what was once a lush, forest landscape to a drier, vaster grassland (Maslin et al., 2008). Because of the unique environment of the Eastern African Rift Valley and the limestone caves of South Africa, some of history’s most telling samplings of our early human ancestors have been preserved for some more than 5 million years (Conroy et al., 2008) (Maslin et al., 2008). With persistent efforts by archeologists and anthropologists alike, these valuable locations known as “The Cradle of Mankind” will continue to map out the origin on humankind and explain how environmental factors are the main reason why we are the species we are today
The evidence for human evolution begins with the australopithecines. All the australopithecines were bipedal and therefore possible hominines. In details of their teeth, jaws, and brain size, however, they modify enough among themselves to be divided into five species: Australopithecus anamensis, A. afarensis, A. africanus, A. robustus, and A. boisei. Genus Homo are also divided in five different spices: Homo erectus, H. habilis, H. sapiens, and H. sapiens sapiens.