Many anthropologists believe that modern humans ancestors directly or indirectly killed off Neanderthal and Denisovan populations as they moved into Neanderthal and Denisovan territory. A new study of the issue argues that it’s more likely that Neanderthals and Denisovans were assimilated into the human gene pool thirty to forty thousand years ago during the Upper Pleistocene era as cultural and climatic forces brought the two groups together, according to Arizona State University Professor C. Michael Barton.
Recent sequencing of ancient Neanderthal DNA indicates that Neanderthal genes make up from 1 to 4 percent of the genome of modern populations—especially those of European descent. Denisovans genes (Denisovans are a sister species to Neanderthals, who were recently found in central and eastern Asia).were found to make up 2 to 6 percent of human genes in southeast Asia. South of the Sahara Africans show no signs of Neanderthal genes.
The researchers used archaeological data to track cultural and socio-ecological changes in behavior in Western Eurasia during the past 120,000 years. As Neanderthals and early humans land-use patterns shifted during the last ice age, computer modeling showed that the two populations began to interact and mate, leading to the “extinction” of one of the groups due to hybridization, a well-recognized phenomenon in conservation biology. Neanderthals were limited to western Asia and Europe, while Denisovans, a sister species to Neanderthals, were recently found in central and eastern Asia. Usually it is the smaller population that becomes “extinct” but succeeding hybrid populations still carry some genes from the regional group that disappeared, according to the researchers.
According to Barton, “There is a perception that biological evolution determines culture during the Pleistocene era and that cultural influences only predominate afterwards. The reality is that the two forces have been working together and they were as important 50,000 years ago as they are today. Other than the fact that they disappeared, there is no evidence that Neanderthals were any less fit as hunter-gatherers of the late Pleistocene than any other human ancestor living at that time. It looks like they were as capable as anyone else,”
So why did they assimilate into us rather than us into them? Humans might have had the advantage of a higher birth rate. Neanderthals had slightly bigger heads and brains than humans so they might have had greater difficulty in giving birth. Humans also benefited from their belief that a birth goddess would help them. Without successful reproduction no species can flourish, or even survive. Homo sapiens were as subject to the biological imperative (commandment) to be fruitful and multiply as all other species. But the intelligent minds of Homo sapiens knew the dangers of childbirth. Infant mortality rates in most tribes were more than one in four. The maternal death rate for every four births was more than one in ten. Pregnancy was highly desired and birth anxiously awaited. Pregnant women naturally sought the physical help of their mothers and grandmothers who in turn sought the spiritual help of their now departed mothers and grandmothers. Among the earliest Gods were birth Goddesses. Small stone figures of very pregnant birth Goddesses often referred to as “Venus” figures go back 30-35,000 years. They are the first examples of iconic religion. The worship of spirits within natural phenomena does not need iconic representation. But birth rarely took place in the open or in public. A birth Goddess needed to be present in some tangible way in order to ease the anxiety of women in labor. Even today in some African countries the maternal mortality rate is 3% per birth. A woman who gave birth to 8 children had a one in four chance of dying from giving birth. Any band would benefit even if the presence of Goddesses reduced that mortality rate by only 5%. Carvings in wood of birth Goddesses probably preceded stone statues by many millennia and may have originated 50-100,000 years ago.
A small birth Goddess that fits in the palm of a woman’s hand, carved of Mammoth ivory with exaggerated sexual features was described in the May 14, 2009 issue of Nature. The figurine is dated to more than 35,000 years ago, when all three species were alive. Dozens of these figurines have been found at human sites, none at Neanderthal sites. Indeed, archeological evidence of religious rituals in general is much more extensive at human sites than at Neanderthal sites. Thus, religion may have been the single most significant factor in Neanderthal and Denisovan assimilation into humans rather than human assimilation into them.
For further information see my article in Popular Archeology June, 2011 or my web site: rabbimaller.com
- Possible Neanderthal cave paintings discovered (kottke.org)
- Genes of Extinct Ancestor Survive in Modern Humans (wired.com)
- Do you think we should clone a Neanderthal? [Scifi Ethics] (io9.com)
- Neanderthal demise a variety of reasons (artofthestem.com)
- Are you a bit Neanderthal? (biowaves.wordpress.com)
- ‘One species’ idea finally put to bed? (bbc.co.uk)
- Ancient cave girl genome could crack Man’s genetic puzzle (go.theregister.com)
- Ancient humans just couldn’t stop having sex with Neanderthals [Evolution] (io9.com)
- First Neanderthal cave paintings discovered in Spain (newscientist.com)