But more interesting than the exponential growth in data are the surprising things we have inferred from the data. In the heady early days of the publication of the draft of the human genome over twenty years ago, co-author Francis Collins asserted that the combination of molecular biology and genomics would “make a significant impact” on our attempt to understand and cure cancer. Despite some early instances where genomic sequencing was performed on cancer patients, like Steve Jobs in 2009, the overall impact of the new science on healthcare has been modest at best. Instead, paleoanthropology, prehistory, and history were transformed as genetics surveyed the pedigrees of the human past with a power and precision that would have been unimaginable a generation ago.
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This shocking result only came out through ancient DNA. Not only do modern humans have Neanderthal ancestry, but some of us have Denisovan ancestry. It comprises 5% of the heritage of Papuans and lower fractions of Denisovan ancestry are found throughout Asia. There is an open question in anthropology as to whether humans are naturally promiscuous. The data from DNA shows that our forebears were sexually open to liaisons with populations and people quite different from them, and definitely forces us to lean in one direction in the debate.
Using a genomic clock, Neanderthals and modern humans became separated 600,000 years ago. The most distinct lineage in modern populations, between South African Khoisan and all other humans, clocks in at 200,000 years. Our ancestors’ sexual preferences were evidently very broad. In a cave in Russia, Researchers have even discovered a young girl whose mother was a Neanderthal and whose father was a Denisovan. Statistically, the probability of catching a first-generation hybrid is low; the fact that it was discovered shows that this behavior was common.
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The Roman recollection of the rape of the Sabine women likely reflects cultural memory of events in prehistory, where victorious males obtained mates from the lands they conquered after killing the fathers and brothers of the women they would make wives. Prehistoric human males behaved like lions taking over a pack, killing everyone among the conquered except for nubile females. Genetics shows that since the end of the last Ice Age, paternal lineages are characterized by periodic explosions, where one clan seems to have replaced all the others through a process of competition and polygyny.
Call it the “Genghis Khan effect,” but the Mongolian world emperor was simply the last in a long line of “super-males” that have defined much of the last 12,000 years. They say to believe them when they tell you who they are, and the legends of the Indo-Europeans reflect a patriarchal and warlike culture, destroyers of cities like the god Indra and near-immortal warriors like Achilles, and this is exactly what genetics tell us about them. In prehistoric Sweden, the Neolithic Megalith builders who dominated the region for more than 1000 years seem to have been totally exterminated by the invading “Battle-Axe” culture. The development of agriculture was a new technology that allowed for the expansion of human societies and the emergence of social stratification, but combined with our innate instincts, genetics make it clear that the drive to extermination manifested itself in most places and most times.
We cannot avoid what human nature was for tens of thousands of years in the past. It was bloody, it was brutal, and it was typified by genocide. This is the legacy we inherit, but it is not the legacy we need to replicate. The average life expectancy in the past was also much shorter than in the present, but the application of technology and social institutions has ameliorated the toll that disease takes on the human body. Human societies are also organisms and their rise and fall are measured in the waves of change in the genes of our own species. To the victors go the spoils and the seeds of the future. But institutions like monogamy and a modicum of wealth redistribution can be thought of as social technologies that dampen the volatility inherent in human relationships, a volatility that can manifest in chaos and warfare. Not a war of all against all, but a war where winners took all.
- Read the whole piece by Razib Khan
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