Homo luzonensis: new human species discovered in the Philippines

There is a new human in the archaic block. The researchers announced on Wednesday the discovery of fossils of hominids on the Philippine island of Luzon that do not resemble any human species known to science. After careful badysis, they nicknamed this new species called Homo luzonensis.

This revelation reverberates far beyond the Philippines. It underscores a growing sense among researchers of human origins that human evolution may not be as clear and linear as the story we often tell.

How, however, did a primitive human come to be in such a remote location? And who were your ancestors? The obvious answer is Homo erectus, since that is the only human species that is known to have been in the region well in advance. But H. luzonensis fossils have some characteristics similar to those of previous hominids that are not known to have left Africa.

"Obviously, our idea of ​​what was happening is much less nuanced than what was really happening," says Susan Antón, a paleoanthropologist at New York University, who was not part of the study. "[This discovery] it gives us a different perspective on our place in the world. "

Armand Mijares did not initially realize the meaning of what he had found, but it would change the life of the paleoanthropologist and rewrite human history.

At an archaeological site on the Philippine island of Luzon in 2007, his team unearthed a large variety of ancient animal bones, dating back some 67,000 years. The researchers could not identify the fossils in the field, so Dr. Mijares sent them to a zoological colleague.

"One night he called me on the phone," recalls Dr. Mijares, badociate professor at the University of the Philippines. "He called me, hey, hello buddy, you have human remains!" I said: & # 39; What? & # 39; & # 39; You have a human that remains & # 39; "

Among the ancient bones there was a single human toe. But to what human species did he belong?

Now, after studying more hominid bones discovered on the site in 2011 and 2015, the researchers came to a poignant conclusion: a human species previously unknown to the science that lived in Luzon. The researchers introduced the new species, nicknamed Homo luzonensis, in an article published in the journal Nature on Wednesday.

This finding reverberates beyond the Philippines. It underscores a growing sense among researchers of human origins that human evolution may not be as clear and linear as the story we often tell. H. luzonensis adds even more complexity to that image.

"Obviously, our idea of ​​what was happening is much less nuanced than what was really happening," says Susan Antón, a paleoanthropologist at New York University, who was not part of the study. "[This discovery] it gives us a different perspective on our place in the world. "

Despite giving H. luzonensis a name, the hominid is still mysterious in many ways, and by ordering its history could illuminate the nuances of the entire genus Homo.

Currently, only a handful of bones represent the new species: some bones of hands and feet, part of a thigh bone and seven teeth. All the bones are particularly small, suggesting that this ancient human was probably less than 4 feet tall. But without long bones, it's hard to be sure, says Dr. Mijares, co-author of the new article.

That would do H. luzonensis The second dwarf species known in the genus Homo. The other short human, nicknamed "hobbit" for his stature, was discovered in 2004 on the Indonesian island of Flores. Both of them Homo floresiensis (scientific name of the hobbit) and its new counterpart is believed to have lived until about 50,000 years ago.

Both hominids probably underwent a process known as insular dwarfism, when a species shrinks from generation to generation through evolutionary selection due to limited resources. But in the first place, how they got to the islands and who they were when they arrived, are still open questions.

At the time, Homo sapiensNeandertals and Denisovans were the only other known human species outside of Africa. But becoming hominids as different as the two inhabitants of the islands has generations of evolution, so they probably come from an earlier Homo lineage.

The researchers have previously found Homo erectus The fossils, dated to show the species, were in the region 1 million years ago. So that species is an obvious contender. It is also the only member of the Homo genus known in the region before H. sapiens They arrived about 50,000 years ago, apart from the dwarf humans Flores and Luzón.

The told story of H. erectus the migration from Africa to Asia is something like this: as the first hominid to have long legs suitable for walking long distances, H. erectus He was the first to leave Africa to conquer the world. A population in Southeast Asia somehow managed to reach these islands through wide and deep waters. Some scientists have suggested that hominids may have been dragged out to sea in a vegetation mat or some other accidental event. Once there, they established a population and, for generations, their characteristics changed to better adapt to the environments of the island.

"Do you remember Occam's razor?" Says Russell Ciochon, a paleoanthropologist at the University of Iowa, who was not part of the study. "What is the most parsimonious hypothesis? Homo erectus I arrived there with enough time to disperse and evolve in these different species. "

But others are not so sure.

The Luzon fossils have a strange mix of characteristics (that's what convinced the research team that this was a completely new species). The small teeth are seen as modern and archaic hominins in different ways. And the toe bone is curved, much more similar to the Australopithecus genus than to any Homo.

"We could also explain it as something like the early Homo who leaves Africa at the same time or at the same time. Homo erectus", Suggests Matt Tocheri, a Canadian research professor on human origins at Lakehead University and a Homo floresiensis investigator. H. erectus He was the first member of the genre to have human features throughout his body. The previous members of the genre seemed very human in the face and the head, but from the neck down, they were much more similar to the Australopithecus.

In addition, says Dr. Tocheri, it has been found that stone tools in China date back approximately 2.1 million years, a few hundred thousand years before the oldest H. erectus fossil found outside of Africa.

Such a scenario would be an important rewrite for the conventional stories of early human dispersal, particularly because the legs and feet of Australopithecus adapted more to a dual life as tree climbers and local walkers than long distance walks. And it could still be possible that H. erectus he left Africa sooner than previously thought, and that the hominino of Luzón evolved H. erectus and that those seemingly archaic features were simply better adaptations for the island's environment.

"It's an interesting idea, but I think it would be foolish to commit to one or the other in light of the fact that the data is simply not there to judge," says William Kimbel, director of the Institute of Human Origins at Arizona State University. that was not part of the study. More data is needed, he says.

Older DNA samples would also help, but tropical islands are not conducive environments for preservation. Dr. Mijares and his colleagues tried to extract some of the Luzon fossils, but could not find any that they had preserved.

Some paleoanthropologists hesitate to call the hominin of Luzon a new species yet. "Because Homo is so defined in cranial remains," Dr. Antón says, "I would have wanted some heads."

That does not mean the team is wrong, he adds, but the importance of their finding is not based on whether you can call this hominino a different species. Instead, he says, the fact that a hominin evolved with such different characteristics in the context of the island highlights how flexible and variable humans can be.

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This also shows that human evolutionary history may not be as unique as we like to think, says Dr. Tocheri. "It really looks a lot like the evolutionary record of other mammals, and at the end of the day, hominids are just another mammal."

Dr. Kimbel agrees: "We are exceptional in many ways, but do not be fooled into thinking that our explanations [of how we came to be] They have to be exceptional too. "

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