Analysis Of Multiple Theories Of Human Evolution History Essay
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The study of evolution in and of itself can be controversial to some. However, within the scientific community it is regarded as the broadly accepted idea that every living thing is derived from what came before and the tiny gradual mutations that arose through millions of years. To that end, there is much debate on certain aspects of particular mutations. Specifically, the debate surrounding the circumstances of human evolution can certainly be seen as contentious. Notwithstanding those who disavow evolution in its entirety, within the scientific community itself, there are several different schools of thought. More notably, the differing theories challenge each other with regard to when homo sapiens first appeared. But while each idea of human progression may differ, they are each rooted in strong empirical, but still limited, evidence.
In scientific terms, before establishing how homo sapiens have come to be, we must first examine where they have come from. According to Cynthia Stokes Brown, author of Big History, "Five to 7 million years ago some mutation occurred in an ape ancestor and survived, and from that single mutation other single mutations kept occurring in the branch called hominids, the bipedal apesâ€¦These genetic changes took place repeatedly in the same place-eastern Africa." All major scientific theories regarding human evolution begin with this accepted premise, as Brown states, "For at least 3 million years human development occurred only in Africa; hominids did not live anywhere else, although apes lived in Europe and Asia as well." There is an important point to be made in saying that although apes lived in other continents, human development took place exclusively in eastern Africa. One must acknowledge the distinct characteristics of Africa that fostered bipedal evolution in the first place.
Eastern Africa, with its abundance of animals and plant life, is significant because of how it became conducive to and instrumental in helping shape human evolution. Brown writes,
Eastern Africa is tropical; our lack of hairiness indicates that we evolved from tropical animals. To become humans, tropical apes came down from trees to live on grasslands; we are creatures of grasslands, not forests. The geography that could mold human development is found in the Great Rift Valley of eastern Africa.
This helps one to understand the origin of homo sapiens and what conditions helped bipeds thrive sometime between 1 and 1.8 million years ago. Additionally, in deriving all of this information one realizes the arduous work involved in documenting and compiling evidence that dates back millions of years. One can recognize the power of human thought and reason, a result of evolution itself.
It is in the migration out of Africa where a sometimes contentious debate arises in the scientific community. The distinction is made just after the presence of homo erectus. Whereas one theory describes homo sapiens in direct lineage to the groups of homo erectus which migrated out of the Great Rift Valley region, known as the Multiregional theory, the more widely accepted thought is described as the Noah's Ark Theory. The inference made by that name is that we were all in the same boat, Africa, and then migrated out about 100,000 to 200,000 years ago, some million years after the first homo erectus left Africa. Essentially it boils down to the question of whether or not those who left Africa evolved along with those who remained into homo sapiens or that those who left died off as a different species entirely.
The argument for a multiregional theory of human evolution was first proposed by Franz Weidenreich and is based on his analysis of the Peking Man (Foley). The Peking Man refers to the findings of homo erectus which were discovered in China between the years 1923 to 1927 (Schmalzer). They are estimated to be between 500,000 and 300,000 years old. Although it is apparent that these fossils are in fact homo erectus, the idea Weidenreich wishes to convey is that homo sapiens, and in this case, the Chinese people, are direct descendants from homo erectus as found in geographically disparate locations. However, it is imperative to realize that what is being proposed isn't the idea of parallel evolution. In fact, a point of severe conentiousness arises from the misunderstanding of what the multiregional model suggests.
In his paper, "Genetics and recent Human Evolution," Alan. R. Templeton writes, "[Figure 1A] was not the multiregional model being debated at the time (except to some of the advocates of replacement). The multiregional model was formulated by the anthropologist Franz Weidenreich." The model he refers to as incorrect suggests that the groups that migrated out of Africa evolved in isolation to eventually become homo sapiens. Templeton continues to say, "This model was already largely discredited just on the basis of the theoretical implausibility of such a threefold parallel evolution." However, the model Weidenreich sought to promote was based on the idea of perpetual gene flow and interconnectivity. The follow figure displays the flawed Candelabra, African replacement (Noah's Ark theory), and Weidenreich's Multiregional theory:
Once one reconciles these to be three distinctly different theories, the idea of a multiregional evolution, with a constant flow of gene-sharing, suddenly carries greater weight. But it is worth noting that even Cynthia Brown, in Big History, refers to candelabra as being synonymous with multiregionalism. And while it is argued by proponents of the true multiregional hypothesis, that such interbreeding of disparate groups of homo erectus could account for certain disparities and characteristics of particulular locations, proponents of African replacement would consider that a result of vast migration by homo sapiens after leaving Africa.
The "out of Africa" theory, having the hypothesis that homo sapiens evolved in Africa and only left 100,000 or 200,000 years ago, is largely credited to anthropologist Chris Stringer and Peter Andrews. However, this theory too has its own disagreements. There is a debate amongst scientists as to whether there was one large dispersal of humans out of Africa, as argued for by Richard Klein in his book, The Human Career, or if there were several excursions out of Africa. The latter theory infers that following the evolution of modern humans in southeastern Africa, population began to expand through the African continent. Furthermore, it is believe that one of these populations, around 70,000 or 60,000 years ago migrated out from the Horn of Africa, across the strait of Bab el Mandeb, remaining along the southern Asian coast, and eventually into southeast Asia and Australia while another group of modern humans left from northeast Africa to the Levant and subsequently Eurasia around 50,000 and 45,000 years ago. The second group is associated with more sophisticated tools (Lahr & Foley). Cynthia Brown provides an explanation for the possible discrepancy in migration periods:
Some of them [homo sapiens] managed to move-in a short period of opportunity provided by Earth's climate-out of the tropical savannas into the area of the eastern Mediterranean that is now Israel, Palestine, Syria, and Lebanon. Then, about 90,000 years ago, Earth tipped back into a cold glacial period in which the Sahara Desert rapidly dried up, preventing further human crossing until warmer, wetter times.
This gives weight to the idea of two distinct mass migrations and helps understand its possibility.
It is important to note that the idea of evolution, while it has been accepted by the scientific community for some time now, still faces criticism from some parties. Most notably are the devoutly religious. As Brown puts it, "Some people in the Judeo-Christian world, as do people in other religious traditions, reject the findings of science and continue to believe that God created the world as it is just a few thousand years ago." While these groups of people are broadly known as creationists, it must be understood that there is no logical reason or scientific basis to their understanding of the world. Moreover, it is of enormous importance that such denominations not be able to rebrand their logic-less beliefs as "intelligent design" or whatever name they might establish in the future. The fact of the matter is that these ideas come from the corners of the mind that have been unfiltered by reason and thought and deserve little serious attention other than to acknowledge that for some, the capacity for intelligent thought, as made possible by the brain, remains in need of further evolving.
With respect to in class discussion, most notably, "The Strange Death of Silas Dean," one begins to understand how history, though subject to interpretation, is more than just the series of events that as gotten humanity from there to here. In fact, as James West Davidson describes it, "History is not "what happened in the past"; rather, it is the act of selecting, analyzing, and writing about the past. It is something that is done, that is constructed, rather than an inert body of data that lies scattered through the archives." That is to say that, while details are of great importance, it sometimes not imperative to know that all mammals have fur and generally live in smaller closely knit communities. Although a good piece of information to know, and certainly a part of history that will lead to the evolution of modern human beings, it is superfluous to the debate of how evolution pushed an ape into a biped. Moreover, it helps for one to be judicious in their findings. Sometimes during an excavation, one might find what appears to be a fossilized tooth belonging to the oldest homo sapiens ever, a relic of our ancestry, a guiding light in the continuity of the puzzle known as life, but sometimes it's just a rock.
On the other hand however, is the fact that the more information one accumulates, the broader their understanding. It is in the presentation of ideas that necessitates a change in scope. However, that is not to say, a need to revise history. It behooved proponents of the African replacement theory to group the Candelabra theory with the multiregional hypothesis just as it benefits North Korea to limit its citizens capability to reach the outside world. Obscurity only serves to debilitate the mind's ability to sift through the banks of knowledge that humanity possesses. And in congruence with obscurity is an inability to accept new information that is so diametrically opposed to one's own understanding. It is for that reason that the overtly religious find themselves unable to accept change. It is ironic, change is the only element one has control over that gives him the ability to survive. Evolution itself is based on a creature's ability to adapt to its surroundings as a means of survival.
Through a great many researchers and scientists, we're able to discern certain facts of our past. Religion withstanding, we are able to agree that homo erectus came to be in the grasslands of southeastern Africa no more than two million years ago. While a debate continues, I am at the moment led to believe that modern humans came to be in Africa and then migrated away. However, I am only able to reach this conclusion based on the information I have found. Either there might be more to learn that could sway my thoughts or they might be more evidence remaining in the sedimentary annals of time. Again, it returns us to the idea of perspective history. Furthermore, I accept that two separate migrations happened after homo sapiens appeared. But seeing as the scientific community is still in the midst of a debate, it is safe and beneficial to say that my mind is not of concrete and is malleable enough to remain receptive to new information. Although we are bound to stir up controversy as change always has, perhaps we may take solace in a simple in the knowledge that humanity has been able to thrive as a result of thought, of our ability to invent. From the first person to sharpen a rock, we have always been and will continue to evolve.
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