Have you ever wondered what happened to the ancient Neanderthals? Genome sequencing may help provide some answers to your questions. When Homo sapiens migrated out of Africa, Neanderthals already lived in the Middle East. But geneticists who compared Neanderthal and modern human genome sequences have discovered something completely unexpected: The genomes of modern Europeans and Asians – but not Africans – contain small amounts of Neanderthal DNA. This suggests that Homo sapiens and Neanderthals interbred and their descendants went on to settle Europe, Asia, and the Americas. It’s possible, depending on your ancestry, that your cells contain part of the Neanderthal genome!
DNA from a previously unknown line of ancient humans was extracted from a fossilized fingertip found in Denisova Cave in Russia in 2008. Genomic sequences of the “Denisovans” have also been identified in the genomes of Papua, New Guineans, and Aboriginal populations in Australia and the Philippines.
Svante Pääbo and his team of researchers at Germany’s Max Planck Institute for Evolutionary Biology have developed methods for retrieving ancient DNA from early human fossils. With a dentist’s drill, they remove bone powder from fossils and extract the DNA for sequencing. Using the ancient DNA extracted from fossils, researchers at NIH and the Broad Institute collaborated on analyzing the Neanderthal and Denisovan genomes.
The Neanderthal bones found in Vindija Cave, in Croatia, dated from 38,000 to 44,000 years ago. It took more than 10 years for researchers to sequence DNA from the three fossils, which were contaminated by bacteria as well as DNA from researchers who handled them.
Geneticists who compared Neanderthal and modern human genome sequences discovered something completely unexpected.
The tiny fossilized Denisovan fingertip is estimated be about 80,000 years old. DNA extracted from this fossilized pinky finger yielded a sequence just as accurate as for living humans. Scientists can tell that the young girl probably had brown eyes, hair, and skin. Studying fossil remains and human anatomy helps scientists picture how ancient human species may have looked. But with so few Denisovan fossils, we know very little yet about their anatomy.
Not all scientists agree about the source of ancient DNA in modern human genomes. Some researchers suggest that the Neanderthal and Denisovan DNA in human genomes indicates a common ancestor rather than interbreeding. However, most studies support the idea that the species interbred.