Casey Leonard. Multiregional model vs. Out of Africa theory SLCC

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1 Casey Leonard Multiregional model vs. Out of Africa theory SLCC

2 2 It is debated where humans came from and how they spread across the world. Since people don't all look the same, or are categorized into "races", that we can adapt to different environments and can change. It would seem that humans originated in Africa and then moved outward to Europe and Asia. Scientist ask the question did humans replace Neanderthals or did they interbreed with them? The out of Africa model suggests that humans descended from a group in Africa then left the continent and replaced Neanderthals. The multiregional model would suggest that humans bread with subspecies to create what we have today and overtime adapted to regions that made humans different in features and appearance but similar enough to interbreed and retain similar features. The Out of Africa, or African Replacement Hypothesis, states that every living human is descended from a group in Africa who spread across the world replacing earlier Neanderthals. The Out-of-Africa model is also known as the recent single-origin hypothesis, and Recent African Origin theory. The out of Africa theory is the most accepted theory describing the geographic origin and early migration of modern humans. The concept was rough until the 1980s when it was confirmed by a study of mitochondrial DNA, combined with evidence based on physical anthropology of archaic specimens. "We have combined our genetic data with new measurements of a large sample of skulls to show definitively that modern humans originated from a single area" (Owen, 2007). Genetic studies and fossil evidence show that ancient Homo sapiens evolved in to modern humans in Africa, between 200,000 and 150,000 years ago, and members of one branch of Homo sapiens left Africa between 125,000 and 60,000 years ago,

3 3 and that over time these humans replaced earlier human populations such as Neanderthals. The date of the earliest successful "out of Africa" migration has been placed at approximately 60,000 years ago, as suggested by genetics, but migration out of the continent may have taken place as early as 125,000 years ago according to Arabian archaeology from finds of tools in the region. A 2013 paper reported that an unknown lineage had been found, which pushed the estimated date for the most recent common ancestor back to 338,000 years ago. There are differing theories on whether there was a single migration or several. A multiple dispersal model involves the Southern Dispersal theory, which has gained support in recent years from genetic and archaeological evidence. A growing number of researchers also suspect that north Africa was the original home of the modern humans who first left the continent. The multiregional hypothesis is a substitute scientific theory that provides an explanation for the pattern of human evolution. The term "multiregional hypothesis" was coined in the early 1980s by Milford H. Wolpoff and colleagues, who used the theory to explain regional similarities between archaic humans and modern humans in various regions, in what they called "regional continuity". Some supporters of multiregional evolution say that the transition to what we see today first occurred in Africa and was then shared across the Old World through gene flow, while others argue that modern traits appeared in different times and places, such that modern humans evolved through the coalescence of these changes (Relethford, 2002). The hypothesis holds that humans first arose near the beginning of the Pleistocene two million years ago and following human evolution has been within a single human species. This species includes archaic humans such as Homo erectus and Neanderthals as well as modern forms, and evolved worldwide to the diverse

4 4 populations of modern Homo sapiens. The theory says that humans evolve through a combination of adaptation within a mixture of regions of the world and gene flow between those regions. Wolpoff proposed that the means of variation allowed for the necessary balance between both local selection and overall evolution as a global species, with Homo erectus, Neanderthals, Homo sapiens and other human forms as subspecies. This arose in Africa two million years ago as homo erectus and then spread across the world, developing adaptations and features to suit different conditions. Some populations became isolated from other groups for periods of time, but through continuous interbreeding, replacement, genetic drift and selection, adaptations would form according to regional factors. By these adaptations, surviving local populations of the species evolved into modern humans, retaining some regional adaptations but with many features common to all humans. The out of Africa theory seems to be the most logical of the two models. Modern DNA testing and research seems to support the out of Africa theory where as there is little evidence supporting the multiregional theory. This theory is now highly discredited by many scholars due to the lack of supporting evidence. It was once thought that the fossil records from Australia and Asia could be understood as showing evidence for such regional continuity (Edwards, 2012). In recent years multiregional theory has been disproven more and more with the out of Africa theory having more and more evidence. Testing would show that earlier beings such as Neanderthals died out where humans could survive and take over.

5 5 Works Cited Edwards, S. (2012, July 7). Analysis of two competing theories on the origin of homo sapiens sapiens: Multiregional theory vs. the out of africa 2 model. Anthrojournal,1, 1. Retrieved from Owen, J. (2007, July 18). Modern humans came out of africa, "definitive" study says. National Geographic. Relethford, J. (2002). Ancient dna and the origin of modern humans. Evolution, 527. Link: