TThe human The species is a lonely one. Today there are two species of gorillas, two of chimpanzees and a whopping three species of orangutans, but only one species of human. It was not always like that. People are familiar with the idea that Homo sapiens Once shared Eurasia with another human, H. neanderthalensis. In 2004, researchers announced with great enthusiasm that they had found the bones of a third contemporary relative, a rather short human species that lived on the Indonesian island of Flores. This became H. floresiensis, and was quickly nicknamed the "Hobbit". Then, in 2010, geneticists declared that a single finger bone found in a cave in the Altai Mountains, in western Siberia, carried a different genome that suggested it belonged to a fourth group, the Denisovans.
Two new studies reveal that the landscape the ancestors of H. sapiens Wandering through was even more crowded, until quite recently. One report is based on the power of genetic sequencing to show that denisovans comprised at least three different populations, which evolved separately for hundreds of thousands of years. The other study announces a completely new species of hominids, H. luzonensis. Both findings focus on the islands that lie on the margins of the ancient world; in Southeast Asia, a region that until recently has been ignored by paleoanthropologists.
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The flashes of the new species occurred in 2010, when a collaboration of Filipino, French and Australian researchers announced that they had found a bone similar to a human (pictured opposite) in Luzon, the largest island in the Philippines. The bone was 67,000 years old, which means that its owner was alive shortly before. H. sapiens He ventured out of Africa. It was discovered next to animal bones slaughtered on an island separated from mainland Asia by a sea. All this pointed to a fairly sophisticated human, capable of creating sharp cutting tools, and possibly also could build and direct a boat or raft (although some argue that it may have floated, or swum to the islands).
The same team, led by Florent Détroit of the Musée de l'Homme in Paris, reports in Nature This week, next to the foot bone, they also found two finger bones, two toe bones and several teeth. Of these, they have identified at least three individuals with characteristics that indicate that they belonged to a new species of human.
The fossil remains of H. luzonensis They are bizarre The bones of the toes, for example, suggest that they adapted to climb trees and walk on two legs, something more typical of distant australopithecine relatives who lived millions of years ago in Africa. Luzon's premolar teeth also look primitive, but the molars are modern and H. sapiens-I like it. As with the Hobbit, it is likely that these characteristics have evolved in H. luzonensis As a result of his life on the island. Previous studies have shown that when species are isolated, as on an island, unusual characteristics arise.
The islands of Southeast Asia were also home to the mysterious Denisovans. The little that is known about them has more to do with laboratory work than digging in the ground for debris. That's because very few Denisovan fossils have been found. A finger bone, a skull fragment (announced in March) and a handful of teeth are the only physical testimonies of its existence. They are not enough to say what the Denisovans looked like or to badign them a species name.
However, when comparing DNA extracted from the finger bone to the genomes of living people today, researchers have shown that Denisovans and Neanderthals shared a common ancestor about 500,000 to 700,000 years ago, and that they crossed paths with each other and with the direct ancestors of H. sapiens On more than one occasion These matings transmitted new traits to their descendants. Even today, Tibetans have a Denisovan gene that helps them reproduce at high altitudes. And the Denisovans seem to have traveled a lot, with genetic evidence that at some point they could be found from Western Siberia to Indonesia.
Murray Cox, a computational biologist at Mbadey University in New Zealand, and colleagues pushed the badysis further by exploring a new genetic database, which contains modern genomes from the islands of Southeast Asia, a region that is densely populated and it is not represented to a large extent in genetic surveys. The database includes genomes from New Guinea, where previous studies have indicated that modern genomes contain more Denisovan DNA which is found in other regions.
Three is a crowd
As they inform in Cell, Dr. Cox and his colleagues found evidence of not one, but three distinct groups of Denisovans that intersected with the ancestors of modern Papuans. A group, nicknamed D2, evolved separately from the individual whose finger bone was found in the Siberian cave for 12,500 generations, or approximately 360,000 years. That makes it "almost so different from the individual that is in Denisova cave [in Siberia] as it is for the Neandertals, "says Dr. Cox. D2 It evolved separately for more than 300,000 years that H. sapiens It has been around
There could be profound consequences, says Dr. Cox's collaborator, Guy Jacobs, of the Nanyang Technological University in Singapore. For starters, D2 It could have seemed very different from the Siberian individual. "If we are going to call Neanderthals and Denisovans by special names," says Dr. Cox, "this new group probably also needs a new name."
Genetic badysis estimates that the D2 Denisovans crossed with H. sapiens in Papua, about 30,000 years ago, suggesting that they survived the Neandertals for about 10,000 years. Another Denisovan population may have crossed H. sapiens Only 15,000 years ago, researchers say. That would mean that the Denisovans, not the Neandertals, were the last cousins of humanity to disappear, leaving H. sapiens as the only hominid game in the city.
The fact that they have mated in the islands provides part of the first social and behavioral information about this group of early hominids. I like it H. luzonensis or their ancestors, the Denisovans may have been able to navigate, to cross the strong currents of the Wallace Line (see map). Current attempts to reproduce such trips show that this is not an easy task. Successful crossings require crafts and careful planning.
Through his promiscuity with H. sapiensThe Neandertals and the Denisovans transmitted fragments of genetic code that survive in humans today. Some of the fragments identified by Dr. Cox and his collaborators seem to have played a role in the aid H. sapienss It adapts its diet and immune system as it spreads to new regions, and they are still present to varying degrees in modern populations. As Michael Petraglia, a paleoanthropologist at the Max Planck Institute for the Science of Human History in Germany, puts it: "This is a story not only about history, but also about ourselves today."