The Evolution of Modern Humans
Two origins are considered when thinking about the evolution of modern humans. There’s the “Multiregional Model” that concentrates on a multiple origins theory in which the different human populations or races had independent origins and evolved in isolation from each other, and there’s the recent single-orgin hypothesis or the “Out of Africa” which holds that anatomically modern humans evolved in Africa between 200,000 and 100,000 years ago. With this theory humans started to leave Africa after evolving. Both theories support that human evolution began in africa, but the “Out of Africa” theory has gotten much more support over the last decade, but there ...view middle of the document...
Second, implicit within this idea is that the earliest modern humans appeared in Africa. Third, it also follows that the earliest modern humans in other areas should have African features. Fourth, modern humans and the people they replaced should never have mixed or interbred. Fifth, an anatomic discontinuity should be evident between the human fossils before and after the replacement.
Studies on past population bottlenecks that can be inferred from molecular data have led Multiregionalists to conclude that the recent single-origin hypothesis is untenable because there are no population size bottlenecks affecting all genes that are more recent than the one at the beginning of the species, some 2 million years ago. Multiregionalists claimed that the discovery of a possible hybrid Homo sapiens X neanderthalensis fossil child at the Abrigo do Lagar Velho rock-shelter site in Portugal in 1999 further supports the Multiregional hypothesis, by reflecting the inter-mixture of diverse human populations. Other archaeologists dispute this: the analysis by Duarte et al. of the Lagar Velho child's skeleton is a brave and imaginative interpretation, of which it is unlikely that a majority of paleoanthropologists will consider proven.
“Out of Africa”
This hypothesis claims that after archaic sapiens spread from Africa to Asia and Europe, modern sapiens evolved from archaic sapiens in Africa, and then spread throughout the world. Following this “second expansion,” the modern sapiens replaced the archaic sapiens without interbreeding with them to any appreciable extent.
Therefore, the Out of Africa hypothesis concludes by stating that this African population migrated into Europe from Africa and excluded Neanderthals and the hominids living there at the time.
Support for “out of Africa”
Up until recently the only way of learning about ancient ancestors was through old fossils and stone tools. As we travel further back in time fossils become more rare. Of the billions of people who lived before the invention of agriculture only the fossilized remains of a few hundred have been found. In the absence of fossils, human DNA that transmits genetic information from one generation to the next has proved to be a valuable tool in recording the evolution of the human species.
Two pieces of the human genome are particularly useful...