Using the latest scientific methods, Tom Higham and Katerina Douka from the University of Vienna want to solve a great mystery of human evolution: why are we the only humans left? Higham and Douka were the first to find first-generation offspring of two different types of humans. They are constantly publishing new results in high-impact journals, most recently in Science Advances.
Our ancient cousins are more present in modern human DNA than we thought: modern humans have a small proportion of genes from archaic groups like Neanderthals. Each person of European or Asian descent has an average of two percent Neanderthal DNA in their blood. For people of African descent, this number is lower. This not only explains certain genetic dispositions in modern humans, but it is also evidence that different human species had contact over 40,000 years ago.
HOMO SAPIENS: THE ONLY SPECIES REMAINING AT EIGHT OR MORE?
Examining ancient bone and tooth fragments is the daily work of molecular archaeologists Tom Higham and Katerina Douka. The two have worked with others over the past 15 years to better understand what happened during the crucial period of the Paleolithic, or Old Stone Age. It’s likely that there were at least eight different species of humans on Earth (perhaps even more) 150,000 to 30,000 years ago – and they sometimes exchanged genetic material through interbreeding. “Today is a very unusual time in terms of human evolution.” Tom Higham explains: “For many millions of years we shared the planet with different groups of hominids related to us and now it’s just us and our great ape cousins.”
DISCOVERING AN ANCIENT HUMAN HYBRID
A tiny bone that Katerina and Tom analyzed in the Denisova Cave in Siberia is probably one of their most important finds for research into ancient human history. Katerina Douka explains: “There have been fierce debates between groups of researchers about whether different species may have come together. Other scientists did not believe that species co-existed or even met. This situation changed profoundly in 2010 with the publication of the Neanderthal genome, which showed that living beings shared part of their DNA. Humans had indeed interbred with Neanderthals.
But how common was this? It seems to have happened more regularly than we thought. “In 2015, we found a tiny fragment of human bone using a revolutionary collagen fingerprinting method called ZooMS. Ancient mitochondrial DNA from the bone originally attributed it to a Neanderthal. However, after fully sequenced it, we discovered that it belonged to a 13-year-old girl whose mother was Neanderthal, but whose father was Denisovan. It was the first time anyone had discovered a so-called ‘F1 hybrid’, a first-generation offspring of two different types of humans,” says Katerina Douka.
SCIENTIFIC BREAKTHROUGH WITH CUTTING-EDGE METHODS
“Before 2010, such analyzes were not possible because the methods did not exist then. We can now take a few milligrams of powder from tiny archaeological bone fragments and identify the bones to species, thus finding hidden potential human bone fragments, like this small bone from Denisovan. It’s amazing how the methods of examining human remains have improved so dramatically,” enthused Tom Higham. “The past 20 years have seen an explosion of methods we can apply to answer key archaeological questions.”
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