|San José State University|
& Tornado Alley
in Light of Recent DNA Evidence
About twenty years ago there was a heated intellectual debate about the origin(s) of modern humans. On one side there was the Out-of-Africa hypothesis proposed and supported by paleoanthropologist Christopher Stringer of the Natural History Museum in London. According to the Out-of-Africa hypothesis modern humans (Homo sapiens) originated in Africa and some migrated out and spread around the world as different races. Opposed to this hypothesis was the Multiregionalism hypothesis of Milford Wolpoff of the University of Michigan and its Museum of Anthropology. According to Multiregionalism Homo erectus migrated out of Africa about two million years ago and evolved into Homo sapiens in several locations around the world.
The Out-of-Africa hypothesis won the debate despite the stalwart efforts of Wolpoff and others to defend Multiregionalism. The Out-of-Africa hypothesis was modified in several interesting ways. It is now believed that there was an unsuccessful migration out of northeast Africa (Suez) about a hundred thousand years ago. That migration died out or retreated back to Africa. The modern human population of the world came out of Africa fifty thousand years ago from the Horn of Africa to the Arabian Peninsula. The migration traveled along the coast of Arabia, the Persian Gulf, South India and Australia. There were branches that went into central Asia and Europe.
In Europe and western Asia there were the Neanderthals who evolved from Homo erectus. They occupied Europe and western Asia from about 230,000 BCE to 30,000 BCE. So there was a twenty thousand year overlap of modern humans and Neanderthals.
The skeleton of the modern gracile humans was superior to that of the Neanderthals, enabling them to hunt over a wider range each day than the Neanderthals could. Probably this led to the extinction of the Neanderthals.
It was long thought that humans and Neanderthal did not interbreed because no bones were found that reflected a hybridization. But five or so years ago geneticists learned how to replicate the Neanderthal DNA enough to carry out an analysis of Neanderthal genes. They then found some of those genes in modern humans, about one to four percent. East Asians have a slightly higher proportion of Neanderthal genes than do Europeans. This indicates that East Asians evolved in western Asia.
All of this was very interesting but the real shocker came in January of 2014 when two articles were published in the most prestigious science journals of the U.S. and the U.K. The geneticists looked only at the genes having to do with physical appearance such as skin pigmentation and hair type. They found that 70 percent of the genes of Europeans and East Asian having to do with physical appearance are Neanderthal genes. European and East Asians may be genetically African but they do not look like Africans. The have light skin pigmentation because in the temperate zones of Europe and East Asia light skin pigmentation has a definite survival value for getting vitamin D from ultraviolet light. It is not obvious what survival value straight hair has over tightly curled African hair but it must. Long straight hair may give significant protection from the cold.
Europeans and East Asians look like Neanderthals. There has been a conscious effort to depict Neanderthals as ugly. That is unjustified.
Then the picture widened. In western China there is a cave named Denisova that was found to contain bones that were neither Neanderthal nor modern human. The DNA from these bones was analyzed genetically and subsequently some of those genes were found in the DNA of people living in New Guinea. Later Tibetans were found to have a gene from the Denisovans that enhanced survivability at high altitudes. Apparently the subspecies of Denisovan evolved from Homo erectus and occupied East and Southeast Asia.
Some researchers gathered Y chromosome data for almost seven thousand males. A male inherits his Y chromosome from his father who in turn inherited it from his father. Except for mutations human Y chromosome should trace back to some common ancestor. The researchers did find that all but one in their sample traced back to the same human ancestor. That single exception was an African American. The researchers then checked the Y chromosomes in an area of Nigeria and the Cameroons and found a whole community whose males had Y chromosomes that did not trace back to the human ancestor that most of their samples did. Apparently there was a subspecies in that region that humans mated with just as Europeans and East Asians mated with Neanderthals.
The other significant finding of this research is that all of the surviving human-Neanderthal matings were those with a modern human father and Neanderthal mother. There may have been some genetic element of survivability based on parentage. The offspring of lion-tiger matings differ depending upon the species of the mother. The absence of survival of human-Neanderthal offspring in which the father was Neanderthal could be connected with Neanderthal males not being as good at hunting as modern humans.
In a genetic study of Australian aborigines and other native peoples of the region was just published in July of 2016 in the journal Nature Genetics which argues that the modern human migrants out of Africa mated with another hominid subspecies on their way to Australia. The study found that there are genes in the Australians' DNA cannot be attributed to any other source. This is a second big surprise concerning the genes of Australian aborigines. Recently it was found that ten percent of their genes came from South India. Apparently about four thousand years ago ships from South India made it to Australia and could not return.
The Out-of-Africa and Multiregionalism hypotheses can be synthesized. Homo erectus evolved into separate subspecies in areas around the world. When modern humans came out of Africa they mated with the local subspecies. The descendants had only a small proportion of the subspecies' genes overall, say 3 percent, but in terms of appearance they got a high proportion of the subspecies genes, say 70 percent. What we think of as race is largely a matter of physical appearance and that a race gets from their local subspecies ancestors. So the Out-of-Africa hypothesis is correct in terms of overall genes but Multiregionalism is correct in terms of physical appearance.
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