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Meet your long lost cousin Homo luzonensis

  Callao Cave in the north of Luzon, where the fossils were found.
Enlarge / Callao Cave in the north of Luzon, where the fossils were found.

Detroit et al. 2019

Our picture of the development of hominin in Asia has been complicated by the discovery of a hitherto unknown hominin species on the island of Luzon in the Philippines. The new species Homo luzonensis lived about the same time as the hobbits of nearby Flores ( Homo floresiensis ).

The two species share a mixture of modern and modern older features. Homo luzonensis & # 39; teeth look like those of the newer members of our genus, homo but the hand and foot bones look more like they could have belonged to an Australopithecine ̵

1; an early one Human relatives that evolved about 3 million years ago and spent as much time in the trees as on the ground, a group that contained the famous skeleton called Lucy.

The combination did not look like any other anthropologist they had seen before. [19659005] Everything we know about Homo Luzonensis comes from a handful of bones and teeth from the Callao Cave at the northern end of Luzon in the Philippines. The site has been dated to a uranium series of at least 67,000 to 50,000 years. In 2011, a team of archaeologists led by anthropologist Florent Détroit of the National Museum of Natural History in Paris found two toe bones, two finger bones, seven teeth, and the femur shaft in the same sediment layer. In 2007, they had a foot bone (metatarsal bone). found. These bony parts are all that's left of at least two hominin adults and one child who died about 50,000 years ago. Archaeologists found two upper right molars, meaning that the teeth came from at least two adults. By now the femur clearly belonged to a child.

These three hominins were not our ancestors. instead, they probably descended from species such as Homo erectus which spread out of Africa about 1.5 million to 2.0 million years ago, long before the ancestors of Neanderthals and Denisovans ventured into Eurasia 500,000 years ago ( just to follow) and eliminated by modern humans about 200,000 years ago). So you can imagine Homo luzonensis as a distant cousin – one of several who co-existed around the world until 50,000 years ago.

My little teeth you have!

Two million or three million years ago, hominins such as Australopithecines and the first members of our Homo genus had massive, heavy jaws and large, robust teeth supported by strong muscles that required thick anchor points on the skull. Over time, hominin diets shifted to foods that required less chewing work. Therefore, humans and our younger relatives tend to have smaller, less strong jaws and teeth with more subtle anchoring points on the skull. That's why some Australopithecines have cool sagittal ridges, and we do not.

The teeth of Calloahave Homo luzonensis are more similar to those of more recent members of our genus than Lucy. They are as small as ours and have easier occlusal surfaces. Their overall form looks more like Homo from the last 2 million years, though they are not quite as square as ours. In some other features, however, traces of earlier lineages are seen, such as the size difference between the premolars and the molars.

Overall, Homo luzonensis shows a pattern that is not seen elsewhere in the genus Homo "wrote Détroit and his colleagues in an article published today in Nature , In other words, the teeth look different than any other species, so it's probably a species we've never seen before.

But on the other hand …

The few hand and foot bones of Homo luzonensis are more like Australopithecines. One of the finger bones (the middle bone of a left hand finger) and a toe bone (the base of one of the middle toes of the right foot) are both curved, as you would expect in older members of our pedigree, such as Australopithecus afarensis , And the way in which the end of the toe jointed with the metatarsal bone (a bone in the middle of the foot) looked more like an Australopithecine than Homo erectus or a modern man.

You could drop that bone among Ethiopia's fossils in Hadar 3 million years ago, and you could not pull it out, "anthropologist Matthew Tocheri of Lakehead University, who wrote an article about the discovery, told Ars Technica , "I do not think there is anyone in the field who would say that this looks like the toe bones of Homo erectus from 19459017 look like this. Instead, it's just the opposite. They hypothesize that the toe bone of Homo erectus is much more like our toe bones, where they are much shorter and the morphology has changed dramatically, as we saw in earlier hominins. "

Curved phalanges are usually the mark of a life spent climbing. Bones are constantly rebuilding themselves throughout our lives, and their final shape reflects the burdens we subject them to. If you were an early hominin, you would climb about as often and hang around in trees as you were walking on the ground. After spending a lot of time grabbing branches with your weight under your arms, the bones at the base of your fingers would curve slightly to better support the strain. Curved toe bones suggest clinging to the feet.

This reveals more about an individual's lifestyle than his genetics, but might suggest that Homo luzonensis navigated the world with a mix of walking and climbing, much like Lucy and other Australopithecines first appeared three million years ago.

Of course, two fingers and two toes are not much to do, and Détroit and his colleagues warn that we do not have enough information about Homo (19459016) luzonensis to draw firm conclusions on the way things are the kind moves. They say, however, that the bones look significantly more australopithecine than Homo (19459016), and that could mean that human history is more complex than we thought.

Intrigues in the Family Tree

Homo luzonensis lived and died only 2,800 km from the Indonesian island of Flores, where archaeologists discovered the hominin species Homo fossil remains of a diminutive floresiensis . The hobbit was named 100,000 to 60,000 years ago. This discovery was a strong indication that the story of Homo erectus and its descendants among the islands of Southeast Asia may have been more complicated than we thought – and it took a long time for Denisovans and modern humans to emerge

"These new ones Fossils and their assignment to a new species ( Homo luzonensis ) fulfill one of the predictions made by Mike Morwood and others (myself included) when we first reported (15 years ago!)) Discovery of Homo floresiensis : that other unknown hominin species could be found on the islands of Southeast Asia, "said anthropologist Richard Roberts to Ars. (He is a co-discoverer of Homo floresiensis and has his seat at the University of Wollongong.) "Although a new species in the region is in some ways not unexpected, it is still exciting to see this new M aterial to finally come to light.

And there is the fascinating (but totally speculative, so far) prospect that others may still be waiting to be found.

Both Luzon and Flores had been separated from the mainland long ago Hominins ventured into the region so that all groups of hominins (which may have been accidentally washed ashore) reached the islands for hundreds of thousands of years would. As a result, they could develop in their own directions. The result could have been a sudden branching of the hominin tree into several new species. Today, they offer anthropologists the opportunity to play the same story on different tropical islands in parallel. Homo luzonensis and Homo floresiensis have enough in common to point out a common ancestor. "The skeletons of both species have anatomical features that are either rare or absent elsewhere in the genus Homo have similarities to Australopithecus," wrote Détroit and his colleagues. It is likely that the two species have a common ancestor that they do not share with us, much as we are more closely related to Neanderthals and Denisovans than to Homo erectus . At the moment, however, there is still insufficient evidence, and so far, no DNA from either species.

A Family Secret

The most accepted version of this idea is that this common ancestor is Homo erectus . There is fossil evidence of the species' presence in Asia during the proper period from which Homo luzonensis emerged, and there is no fossil evidence for other hominin species at the same time in the region. When the authors made a statistical analysis of all the traits they could quantify, [H.] H. Luzonensis looked more like Asian Homo erectus specimens than any other known species. They suggest that themselves Homo floresiensis & # 39; has developed dwarfism on Flores (and we know that the same happened to modern humans on the island) and that Homo luzonensis & # 39; Australopithecine-type feet and hands were developed on Luzon in a manner that happened to resemble its former relative.

But Tocheri, whose work focuses on hands and feet, says that this is possible, but he argues that this is less likely than the idea that other members Homo can be Africa about the same Time as left Homo erectus. From this point of view, Homo luzonensis and Homo floresiensis look a bit like the earlier hominins, for in fact they are the ones they descended from. Several species, such as Homo habilis and Homo rudolfensis which developed earlier and had more Australopithecine-like features, were still near, as Homo erectus its Eurasian Expansion began. and Tocheri says that 2.1 million year old stone tools found in China last year may indicate an even earlier migration of hominines.

"If we have missed those species that lived less than 100,000 years ago, how much are we missing? previous development phases? "Anthropologist John Hawks of the University of Wisconsin, co-discoverer of Homo Naledi said Ars in an email commenting on the study. "Could it have previously come to disputes that we have not noticed due to bad search strategies and false assumptions? I would not bet that hominins were from Africa much earlier than we thought. "

At the moment we have no direct fossil evidence in one way or another, and what we have comes late Homo luzonensis and Homo floresiensis & # 39; time. Stone tools and slaughtered animal remains on both islands suggest that hominins were there as early as 700,000 years ago. If one finds out if these early residents looked more like Lucy, or more like Homo erectus this could help to solve the family secret.

Nature 2019. DOI: 10.1038 / s41586-019-1067 -9; (Via DOIs).

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