(below 20%) in less than half of the Melanesian groups who speak Austronesian languages, and which was entirely absent in the Papuan-speaking groups. The study found a high rate of genetic differentiation and diversity among the groups living within the Melanesian islands, with the peoples not only distinguished between the islands, but also by the languages, topography, and size of an island. Such diversity developed over the tens of thousands of years since initial settlement, as well as after the more recent arrival of Polynesian ancestors at the islands. Papuan-speaking groups in particular were found to be the most differentiated, while Austronesian-speaking groups along the coastlines were more intermixed. Further DNA analysis has taken research into new directions, as more Homo erectus races or sub-species have been discovered since the late 20th century. Based on his genetic studies of the Denisova hominin, an ancient human species discovered in 2010, Svante Pääbo claims that ancient human ancestors of the Melanesians interbred in Asia with these humans. He has found that people of New Guinea share 4%–7% of their genome with the Denisovans, indicating this exchange. The Denisovans are considered cousin to the Neanderthals. Both groups are now understood to have migrated out of Africa, with the Neanderthals going into Europe, and the Denisovans heading east about 400,000 years ago. This is based on genetic evidence from a fossil found in Siberia. The evidence from Melanesia suggests their territory extended into southeast Asia, where ancestors of the Melanesians developed. Melanesians of some islands are one of the few non-European peoples, and the only dark-skinned group of people outside Australia, known to have blonde hair. The blonde trait developed via the TYRP1 gene, which is not the same gene that causes blondness in European blondes. History of classification Early European explorers noted the physical differences among groups of Pacific Islanders. In 1756 Charles de Brosses theorized that there was an 'old black race' in the Pacific who were conquered or defeated by the peoples of what is now called Polynesia, whom he distinguished as having lighter skin. By 1825 Jean Baptiste Bory de Saint-Vincent developed a more elaborate, 15-race model of human diversity. He described the inhabitants of modern-day Melanesia as Mélaniens, a distinct racial group from the Australian and Neptunian (i.e. Polynesian) races surrounding them. In 1832 Dumont D'Urville expanded and simplified much of this earlier work. He classified the peoples of