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There is a new human on the archaic block. Researchers announced Wednesday the discovery on the island of Luzon, Philippines, of hominins fossils that do not resemble any human species known to science. After a careful analysis, they nicknamed this new species Homo luzonensis.
This revelation is reflected far beyond the Philippines. This highlights the growing sentiment among researchers of human origin that human evolution may not be as sharp and linear as the story we often tell.
How, however, did a young man come to such a remote place? And who were his ancestors? The obvious answer is Homo erectusbecause it is the only human species that we know early enough in the region. But the H. luzonensis the fossils have characteristics similar to those of the earlier hominins, which we do not know that they left Africa.
"Our idea of what was happening is obviously a lot less nuanced than what was really happening," says Susan Antón, a paleoanthropologist at New York University, who did not participate in the study. . "[This discovery] gives us a different perspective of our place in the world. "
Armand Mijares did not at first understand the meaning of what he had discovered, but it would change the life of the paleoanthropologist – and rewrite human history.
In 2007, at an archaeological site on the island of Luzon in the Philippines, his team unearthed a vast array of ancient animal bones, dated to about 67,000 years ago. The researchers could not identify the fossils in the field. Dr. Mijares sent them to a fellow zoologist.
"He called me on my cell phone" one night, recalls Dr. Mijares, an associate professor at the University of the Philippines. "He called me," Hey, my boyfriend, you have human remains! "I said what? "" You have a human being. "
Among the ancient bones, there was only one human bone. But to what human species did he belong?
Now, having studied more of the hominin bones discovered on the site in 2011 and 2015, the researchers have come to a conclusion that upsets history: a human species previously unknown to science once lived in Luçon. The researchers introduced the new species, nicknamed Homo luzonensis, in an article published in the journal Nature Wednesday.
This discovery is echoed beyond the Philippines. This highlights the growing sentiment among researchers of human origin that human evolution may not be as sharp and linear as the story we often tell. H. luzonensis adds even more complexity to this image.
"Our idea of what was happening is obviously a lot less nuanced than what was really happening," says Susan Antón, a paleoanthropologist at New York University, who did not participate in the study. . "[This discovery] gives us a different perspective of our place in the world. "
Despite giving H. luzonensis a name, the hominin remains mysterious in many ways – and the sorting of its history could illuminate the nuances of the whole genus Homo.
Currently, only a handful of bones represent the new species: bones of the hand and foot, part of the femur and seven teeth. All the bones are particularly tiny, suggesting that this ancient man was probably less than 4 feet tall. But without long bones, it's hard to be sure, says Dr. Mijares, co-lead author of the new paper.
That would H. luzonensis the second known dwarf species of the genus Homo. The other little human, nicknamed "hobbit" for his stature, was discovered in 2004 on the Indonesian island of Flores. Both Homo floresiensis (scientific name of the hobbit) and its found counterpart would have survived until approximately 50 000 years.
Both hominins have probably undergone a process known as insular dwarfism, when a species narrows from generation to generation via evolutionary selection due to limited resources. But how they arrived in the islands and who they were when they arrived remain unanswered questions.
At the time, Homo sapiensNeanderthals and Denisovans were the only other human species known to be outside of Africa. But to become distinct hominins, the two inhabitants of the island taking generations of evolution, they are probably from a previous line of Homo.
Researchers have already found Homo erectus fossils, dated to show that the species was in the area a million years ago. So this species is an obvious competitor. He is also the only member of the genus Homo known for his presence in the region before H. sapiens arrived about 50,000 years ago, other than the dwarf humans of Flores and Luzon.
The story told of H. erectus' The migration from Africa to Asia goes a little like this: as the first hominien to have long legs propitious for walking at long distance, H. erectus was the first to leave Africa to conquer the world. A population from Southeast Asia has managed to cross wide and deep waters to these islands. Some scientists have suggested that hominins may have been washed away on a carpet of vegetation or some other accidental event. Once there, they formed a population and, over the generations, their characteristics have changed to better adapt them to island environments.
"Do you remember the Occam razor?" Says Russell Ciochon, paleoanthropologist at the University of Iowa, who did not participate in the study. "What is the most parsimonious hypothesis? We know that Homo erectus arrived with enough time to disperse and evolve towards these different species. "
But others are not so sure.
The Luzon fossils bear a strange mix of characteristics (this convinced the research team that it was an entirely new species). Small teeth look different from modern and archaic hominins. And the bones of the toe are curved, much more similar to the Australopithecus genus than any Homo.
"We could also explain this as if something like a young Homo leaving Africa is about the same time as early Homo erectusSuggests Matt Tocheri, Canada Research Chair in Human Origins at Lakehead University and Homo floresiensis searcher. H. erectus was the first member of the genus to exhibit human characteristics all over his body. Previous members of the genus looked very human to the face and head, but from neck to foot, they looked much more like Australopithecus.
In addition, Dr. Tocheri explains, stone tools dating back about 2.1 million years were discovered in China – a few hundred thousand years before the oldest. H. erectus fossil found outside of Africa.
Such a scenario would constitute a major rewrite of the classic stories of early human dispersion, especially since the legs and feet of the Australopithecus were more suited to a double life of escalator and walker than long distance treks. And it is still possible that H. erectus left Africa earlier than expected, and that the Luzon hominin has evolved from H. erectus and that these seemingly archaic features were simply a better adaptation to the island environment.
"It's an interesting idea, but I think it would be foolish to commit to one or the other in the light of the fact that the data just is not there to judge," says William Kimbel , director of the Institute of Human Origins at Arizona State University, which was not part of the study. More data is needed, he says.
Old DNA samples would also be useful, but tropical islands are not environments conducive to preservation. Dr. Mijares and his colleagues have tried to extract some of the fossils from Luzon, but have found none of those that have been preserved.
Some paleoanthropologists are reluctant to call the hominin of Luzon a new species for the moment. "Because Homo is so defined on cranial remains," says Dr. Antón, "I would have wanted heads."
This does not mean that the team is wrong, she adds, but the importance of their discovery does not depend on the possibility of qualifying this hominin as a distinct species. Instead, she says, the fact that a hominin has developed such different characteristics in the island context underscores how flexible and variable humans can be.
It also shows that the story of human evolution may not be as unique as we think, Dr. Tocheri thinks. "It's really much more like the evolution of other mammals. At the end of the day, hominins are just another mammal.
Dr. Kimbel agrees: "We are exceptional in many ways, but we must not believe that our explanations [of how we came to be] must also be exceptional. "
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