In studying the origin of modern human beings, anthropologists have assumed the science of modeling to determine this origin. Johanson (2001) estimates that about one hundred years ago, different hominid groups occupied the vast areas of Africa, Asia, and Europe; where Africa was occupied by Homo sapiens, Asia by Homo erectus and the Homo neanderthals occupied the regions of Europe. Several decades later, Johanson (2001) notes that these taxonomic variations disappeared as humans gradually evolved in behavior and physical appearance (anatomically). Two schools of thought have since been considered in deliberating the nature of human transformation: the Multiregional Hypothesis and the Out of Africa Model (Johanson, 2001).
The ‘Multiregional Hypothesis’ emphasizes on multiregional continuity as the source of modern humankind while the ‘Out of Africa Model’ suggests a single source for the modern humans. This paper comprehensively analyses the two models and presents their comparisons as argued by various scholars in an attempt to identify the most convincing model.
Multiregional Hypothesis
This model has previously been identified as Multiregional Continuity Model, and it accounts for the evolution of humankind in the Pleistocene (Wolpoff, Hawks and Caspari, 2000). Wolpoff, Hawks, and Caspari define the hypothesis as one that proposes evolution to be a consequence of genetic exchange between the different hominid species. According to Johanson (2001), the Homo erectus is said to have originated from Africa then they moved to other sections of the world.
The Multiregional Hypothesis suggests that speciation was hindered after the migration by some level of gene flow between areas separated geographically. This is in the perspective that without the migration, then similar species could regenerate amongst themselves thereby producing children who are identical to the parents both in genetic and phenotypic traits. With the movement of the erectus species to other regions of Asia, evolved forms of humans developed.
Early hominids were isolated because of an existing relatively large distance between geographical locations. This separation allowed the local populations to develop in differential from each other, thus regional variance (Templeton, 2002). As the Homo erectus moved from Africa to other parts of the world, it is expected that they had to adapt to the new environments. Adaptation is a factor of natural selection; in that those who possess the most suitable traits survive as compared to the ones with unfavorable characteristics (Templeton, 2002). Johanson (2001) states that natural selection is responsible for the races present in the world. For example, the interaction between the African Homo erectus and the Non-African Homo erectus of Europe resulted in white-skinned people occupying the areas of Europe. This is attributed to the low solar intensity experienced in these areas which allow those with lesser melanin (dark skin-color pigment) to survive. In contrast, the black population resided the tropical regions of Africa because of the high solar intensities experienced. The African Homo erectus adapted to the areas’ condition by developing much melanin to avoid effects of solar radiations. It should, however, be noted that this hypothesis is of the suggestion that evolution humanity occurred in areas where the human species existed; lived, and not just where they moved to.
Out of Africa Model
There has been, and still, there are hot debates on which hypothesis is most convincing among the two; Out of Africa Model and the Multiregional. This model asserts that Africa is the cradle land of mankind (Johanson, 2001). The Out of Africa Model suggests that modernity in humankind started in Africa as man evolved and later moved to other parts of the world like Eurasia. Upon arrival in Eurasia, the modern man (Homo sapiens) replaced all the existing Homo erectus. After the Homo erectus migrated into Eurasia, they became reproductively isolated, thus independent evolving that resulted in separate species like the Neanderthals. This theory also forwards an argument that other than modern man originating from one place; Africa (including the Middle East), the ultimate migration of Homo sapiens replaced virtually all the population of Eurasia without inbreeding (Johanson, 2001). The Out of Africa Model proposes that modern humanity is a recent phenomenon.
Multiregional Hypothesis Comparison and the Out of Africa Model
Humanity’s evolution, being a subject, has attracted the attention of many scholars some who criticize or support either of the two. Coon (1962) writes to support the Multiregional theory. Coon maintains that human evolution took place in five stages before attaining the Homo sapiens species which considered modernity of humankind. The development from one step to the other was through genetic change (Coon, 1962). In summary, Coon asserts that evolution of man from Homo erectus to Homo sapiens took place in five stages and not once; a position taken by the Multiregional Hypothesis. Jackson (2001) criticizes this stand taken by Coon and the hypothesis in general. Jackson’s critique tends to align with the proposals of that had been named ‘out of Africa.’
In criticizing the Hypothesis of Multiregional, Jackson faults the idea that evolution took place in five stages. He instead suggests that human beings initially existed as Homo erectus in all parts of the world which could have been five broad geographic regions. These regions could as well be referred to as regions of subspecies. These erectus species individually evolved into the sapient stage without any form of interbreeding. To fully comprehend the controversy surrounding the evolution of humanity, evidence forwarded by the two hypotheses are evaluated in this paper. Johanson (2001) classifies these shreds of evidence as archaeological, genetic and anatomical.
Anatomical Evidences
These evidences focus on the morphological characteristics of the various hominids in different geographical settings as they evolved. Morphological diversification was due to genetic drift and natural selection, (Johanson, 2001) which are attributes of the Multiregional Hypothesis. As earlier indicated under the hypothesis, different hominids occupied the different parts of the world. For example, the Homo erectus occupied Africa and vast areas of Asia while Europe and Western Asia were seized by the Neanderthals. These hominids adapted to the environmental conditions of their respective geographical regions. Johanson illustrates this using the physical appearances of the Neanderthals who lived in Europe at times when the climate was cold; during the glacial periods. The Neanderthals also had a lot of hair covering the skin to protect them from effects of extreme cold (Tattersal, 2009).In contrast, at almost the same glacial period, a creature which resembled the modern man appeared in Africa.
A critical analysis of these anatomical evidence suggests that the modern man (Homo sapiens) and the Neanderthal existed in isolation where each evolved independently as two distinct species. It was also important to mention here that as much as ancient man morphologically evolved to modernity, the case was not same for behavior (Johanson, 2001).
Coon (1962) classified races of the world by morphological characteristics. However, Jackson (2001) is quick to contradict this by drawing support from the ‘new physical anthropology.’ The ‘new physical anthropology’ makes use the principles of genetics and evolutionary theory which treat the difference in the race as ‘population groups’ (Jackson, 2001). This is to mean that race can only be established through genotypic testing and not phenotypic variations or similarities.
Archaeological evidence
The field of archaeology is a science that deals with the study of human remains including artifacts. A study of artifacts from different regions is essential in determining the relation of culture and behavior between the different ancient populations (Galor and Ashraf, 2011). For example, if a similar item were to be discovered in Africa and Europe, then it would be valid to state that the regions were occupied by hominids under the same stage of evolution. This could also suggest that one of the hominid groups could have migrated into either of the areas. Thus unlike the anatomical evidence which clearly confirms the convincing nature of the Out of Africa Model, archaeological evidence tend to support either of the theories. Characteristics of artifacts used by the Middle Stone Age hominids and those used by the Middle Paleolithic Neanderthals had the very close resemblance. According to Johanson (2001), these artifacts included stone stools with little variation. There was a general similarity in tool kits extracted from widely separated geographical areas. These tools, mainly made up of bones, stones, and ivory, were found either at a particular location or different locations.
Four decades ago, the continent of Africa experienced tremendous transformation, tools, and other useful signals. Tattersal (2009) associates this change to the appearance of modern man in Africa; modern in behavior and physical being.
Conclusion
Based on the evidences, this paper finds the Out of Africa Model more convincing in explaining the origin of modern humans. The theories have been used to exclusively explain the origin and evolution of man. The entire models have been used in a way that one would get to understand how man has evolved over the past 1 million years. This suggests that people lived in specified areas or migrated to other regions where they are expected to have carried their culture and way of life. With the reproductive interaction that could be concluded, a genetic exchange is possible. From the view of hominids having lived in one place, it can be concluded that they reproduced amongst themselves thereby allowing for speciation as forwarded by the Out of Africa Model. In both areas of Africa and Asia, there were no signs of living structures.