The genomes of most modern humans are 1–4% Neanderthal — a result of interbreeding with the close relatives that went extinct 30,000 years ago, according to work by an international group of researchers. The team, led by Svante Pääbo, a geneticist at the Max Planck Institute for Evolutionary Anthropology in Leipzig, is reporting only 60% of the Neanderthal genome. But sequencing even this much of the genome was thought to be impossible just a decade ago. “This will change our view of humanity,” says John Hardy, a neuroscientist at University College London who was not involved in the research but studies genetic neurodegenerative diseases.
The drive to sequence the complete Neanderthal genome began about five years ago following the invention of better, faster methods for sequencing DNA. From three Neanderthal bones found in Vindija Cave in Croatia, the team extracted a total of about 300 milligrams of bone. The bones date to between 38,300 and 44,400 years ago, and some have been broken open posibbly to remove their marrow — a sign of cannibalism. Countless fragments of degraded ancient DNA were extracted from the bones, used to create libraries of sequences and then reassembled by computer into the draft Neanderthal genome comprising nearly 2 billion base-pairs. The researchers used the genomes of modern humans and the chimpanzee as references to get the sequence in the correct order. They publish their work in Science this week.