Science Posted on Apr 12, 2019 in Evolution “It’s quite incredible, the extremities, that is the hand and feet bones are remarkably Australopithecine-like. The Australopithecines last walked the earth in Africa about 2 million years ago and are considered to be the ancestors of the Homo group, which includes modern humans,” said Philip Piper with The Australian National University (ANU), about the discovery of fossils of a new species of human in the Philippines, Homo luzonensis is named after Luzon Island, where the more than 50,000 year old fossils were found during excavations at Callao Cave. Co-author and a lead member of the team, Piper says the findings represent a major breakthrough in our understanding of human evolution across Southeast Asia. The researchers uncovered the remains of at least two adults and one juvenile within the same archaeological deposits. “The fossil remains included adult finger and toe bones, as well as teeth. We also recovered a child’s femur. There are some really interesting features – for example, the teeth are really small,” Professor Piper said. “The size of the teeth generally, though not always, reflect the overall body-size of a mammal, so we think Homo luzonensis was probably relatively small. Exactly how small we don’t know yet. We would need to find some skeletal elements from which we could measure body-size more precisely” Professor Piper said. “So, the question is whether some of these features evolved as adaptations to island life, or whether they are anatomical traits passed down to Homo luzonensis from their ancestors over the preceding 2 million years.” While there are still plenty of questions around the origins of Homo luzonensis, and their longevity on the island of Luzon, recent excavations near Callao Cave produced evidence of a butchered rhinoceros and stone tools dating to around 700,000 years ago. “No hominin fossils were recovered, but this does provide a timeframe for a hominin presence on Luzon. Whether it was Homo luzonensis butchering and eating the rhinoceros remains to be seen,” Professor Piper said. “It makes the whole region really significant. The Philippines is made up of a group of large islands that have been separated long enough to have potentially facilitated archipelago speciation. There is no reason why archaeological research in the Philippines couldn’t discover several species of hominin. It’s probably just a matter of time.” Homo luzonensis shares some unique skeletal features with the famous Homo floresiensis or ‘the hobbit’, discovered on the island of Flores to the south east of the Philippine archipelago. In addition, stone tools dating to around 200,000 years ago have been found on the island of Sulawesi, meaning that ancient hominins potentially inhabited many of the large islands of Southeast Asia. The project team was led by Dr Armand Mijares of the University of the Philippines, and includes Dr. Florent Détroit of the National Museum of Natural History in Paris and researchers from the University of Bordeaux, Paul Sabatier University and the University of Poitiers in France, as well as Griffith University in Australia. The Daily Galaxy via ANU and Nature Image at top of page: Australopithecine with thanks to Darryl De Rutter<doc-sep>Callao Cave on Luzon Island, Philippines. Image : Callao Cave Archaeology Project Scientists are reporting the discovery of a previously unknown species of ancient human that lived in the Philippines over 50,000 years ago. Evidence suggests the new species, named Homo luzonensis, was exceptionally tiny—and possibly even smaller than the famous Hobbit species uncovered on the island of Flores in 2004. Advertisement The story of human evolution just got a hell of a lot messier—and considerably more fascinating—owing to the discovery of a previously unknown human species. Bits of teeth and bone pulled from Callao Cave on the Philippine island of Luzon point to the existence of a distinctly human species, one deserving of the Homo designation in terms of its genus. At the same time, however, the fossils found in Callao Cave exhibit features unlike anything ever seen before, thus warranting the declaration of a completely new human species, Homo luzonensis. The details of this astonishing discovery were published today in Nature. Needless to say, this is a huge deal. New human species tend to not be discovered on a regular basis. The discovery of Homo luzonensis, with its curious set of physical characteristics, is telling us some surprising new things about human evolution and what happened to the pioneering hominins who left Africa so long ago. This story begins in 2010 with the important discovery of a single human foot bone, dated at 67,000 years old, in Callao Cave. The exact species could not be determined, but it was the first direct evidence of a human presence in the Philippines. As an important aside, we’ve since learned that hominins—the sub-group of primates that are more closely related to us than to chimpanzees and bonobos—were living in the Philippines as long as 709,000 years ago. A butchered animal bone found a the Kalinga site in Luzon, Philippines, showed hominins were active on the island as far back as 709,000 years ago. The newly discovered species, called Homo luzonensis, lived in the Philippines around 67,000 years ago. It’s not known if the two groups were related. Image : Thomas Ingicco, Mission Marche aux Philippines Indeed, the story of human evolution is getting increasingly complicated. Hominins first appeared in Africa some 6 to 7 million years ago, with the first evidence of a hominid presence in Eurasia dating back about 1.8 million years ago, likely the archaic human known as Homo erectus. Incredibly, this dispersal happened long before our species, Homo sapiens, emerged; we finally entered onto the scene 300,000 years ago, spilling into Eurasia about 100,000 years later. There, we joined two other human species, the Neanderthals and Denisovans. Most extinct hominins are not our direct ancestors, but they’re our very close relatives. Each species went on its own evolutionary journey, adapting to their new circumstances and environments in different ways. By around 50,000 to 60,000 years ago, there were multiple human species living at the same time, doing their own thing at various locations in both Africa and Eurasia. Advertisement The scientists who found the human foot bone in the Philippines, a team led by Florent Détroit from the National Museum of Natural History in France and Armand Mijares from the University of the Philippines, kept working at Callao Cave in an effort to find more clues. These ongoing excavations resulted in the discovery of 12 new hominin elements, including teeth, a partial thigh bone, and several hand and foot bones. These fossils belonged to three different individuals, two adults and one child. No genetic evidence could be extracted from the specimens, and sadly, no skulls were found. These remains were pulled from the same stratigraphic layer as the foot bone found in 2010, dating these individuals to the same time period. Analysis of the bones and teeth suggested a previously unknown species of human. Also, these hominins appear to have been exceptionally small. The authors of the new study suspect H. luzonensis was subject to an evolutionary process known as insular dwarfism, in which a species’ body size becomes significantly reduced over time on account of limited access to resources. A similar thing likely happened to Homo floresiensis, an extinct human species popularly known as the Hobbit. The remains of these diminutive humans, who stood no taller than around 3 feet and 7 inches (109 centimeters), were discovered on the island of Flores in Southeast Asia back in 2004. The discovery of Homo luzonensis—who may have been shorter than the Hobbits—may signify the presence of yet another human species moulded by insular dwarfism—a rather astounding discovery, to say the least. It’s important to point out, however, that insular dwarfism in H. luzonensis remains a distinct, yet unproven, possibility. As the authors noted in the study, “further discoveries and more definitive evidence are needed.” Advertisement The Hobbits and H. luzonensis bear striking similarities, and they were around at roughly the same time, but their evolutionary relationship is not known. It’s conceivable that both human species are descendents of H. erectus, and that both ended up isolated on their respective islands. Five upper teeth of the newly described human species, Homo luzonensis. Image : Callao Cave Archaeology Project Advertisement In terms of the distinct physical differences observed in H. luzonensis, the most notable were seen in their teeth and foot bones. Their molars, in particular, were unlike anything ever seen before in a human species. Writing in an accompanying News & Views article, anthropologist Matthew Tocheri from Lakehead University in Thunderbay, Ontario, described how their teeth exhibited both ancient and modern features. When compared with the molars of other hominin species, H. luzonensis molars are astonishingly small, and the simplified surfaces of their crowns and their low number of cusps are features that look similar to the molar crowns and cusps of H. sapiens. Yet the shapes of H. luzonensis teeth share similarities with the teeth of H. erectus from Asia, and the size ratio of H. luzonensis premolars to molars is similar to that of Paranthropus, species of which are known for their massive jaws and teeth. Advertisement This is unbelievably fascinating, but the story gets even more intriguing—and potentially even more confusing. The third metatarsal—the long bone in the middle toe—in H. luzonensis is exceptionally strange, bearing an uncanny resemblance to those seen in Australopithecus—an ancient human ancestor that lived in Africa some 3 million years ago and never left Africa. Well, at least to the best of our knowledge. H. luzonensis also featured hand bones similar to those of Australopithecus. Advertisement The toe bone in question: The third metatarsal of H. luzonensis. Image : Callao Cave Archaeology Project There are at least two possible explanations for this odd toe bone, neither of which seem wholly plausible. Advertisement Crazy theory number one: Conventional thinking has it that Homo erectus was the only hominin species to have left Africa during the Early Pleistocene, the period between 2.58 to 0.78 million years ago. The evidence found in Callao Cave would seem to suggest that we’ve got it all wrong, and that other hominins, including groups more closely related to Australopithecus (or even Australopithecus itself! ), made their way into Eurasia during this period. More evidence is needed to back this extraordinary possibility. Crazy theory number two: An intriguing aspect about the H. Luzonensis third metatarsal is that it allows for more curved toes. This is significant because curved toes are great for tree climbing and hanging from branches. Australopithecus, a suspected tree climber, was equipped with this particular physical feature, and it would seem to suggest the same for H. luzonensis. But if H. Luzonensis is not closely related to Australopithecus, then why the curved toes and hands? It’s possible that some hominins retained their tree-climbing abilities for much longer than is conventionally appreciated. Another possibility is convergent evolution, in which similar physical characteristics appear in unrelated species. Should this be the case, if would mean that, after thousands of years of upright, bipedal locomotion, H. Luzonensis was returning to an arboreal existence, and evolving the requisite physical characteristics. It’s a mind-blowing theory, no doubt, but again, one in desperate need of further evidence. Advertisement<doc-sep>The announcement of a new species of ancient human (more correctly hominin) from the Philippines, reported today in Nature, will cause a lot of head-shaking among anthropologists and archaeologists. Some will greet the publication with wild enthusiasm, believing it confirms their own views about our evolutionary past. Others will howl angrily, believing the declaration goes way too far with too little evidence. Me, I sit somewhere in the middle of this spectrum of opinions. I’ve long promoted a pluralist view of human evolution and do see the hominin fossil record as strongly suggesting high species diversity. There is no reason to expect human evolution to have been any different to the evolution of other animals where, for example, among our close primate relatives, diversity was and often continues to be the rule. At the same time, each and every new discovery has to stack up and must be judged on its merits, on the basis of the evidence presented. We can’t just accept the interpretation of a new discovery because it suits our strongly held views. But we need also to keep a cool head, because the naming of any new species is still a scientific hypothesis, ripe for testing and far from set in stone, even if published in the esteemed pages of a journal like Nature. The Philippine find So, just what have they found? It’s dubbed Homo luzonensis, after the Philippines’ main island of Luzon, where it was recovered during excavations of Callao Cave in 2007, 2011 and 2015. This new hominin is represented by a handful of heavily worn adult teeth from one or two individuals, one foot and two toe bones, two finger bones, and the fragment of the shaft of a juvenile thigh bone. Its anatomy is argued to be a peculiar mix of features normally found in living humans, Homo erectus, the Hobbit (Homo floresiensis) and Australopithecus. The similarities to Australopithecus are especially intriguing when one ponders for a moment on just who the australopiths actually were. A famous example is “Lucy” who belonged to Australopithecus afarensis living in the Great Rift Valley of East Africa. Another is Australopithecus sediba, from a cave in South Africa and found just a decade ago. These and the many other Australopithecus species (and there are at least six described) lived only in sub-Saharan Africa, between about 2 million and 5 million years ago. Members of Australopithecus were among the earliest hominins who gave rise to the human genus Homo. This makes them one of our own evolutionary ancestors. Yet, despite their definite bipedalism, they also seem to have spent much of their time climbing in trees, perhaps feeding, sleeping and escaping predators. They were typically around 30-50kg, stood 1-1.5 metres tall, and had brain sizes around one-third the size of our own. They may have produced and used crude stone tools, but the evidence remains unclear. In a sense, they would have looked a lot like chimpanzees but with smaller faces and front teeth and with upright bodies. Is it a new species? The statistical comparisons made in the newly published research, led by Florent Détroit of the Musée de l’Homme, highlight a rather odd assortment of features in Homo luzonensis. But the all-important type (or holotype) specimen, referred to as fossil CCH6, comprises just a few teeth from the upper jaw, all of which are rather heavily worn down or broken. There’s not a lot of anatomy preserved here, and this leaves me feeling the case for this new species is a little flimsy. How astonishing would it be that something resembling Australopithecus would have survived a long, long, way from the African Rift Valley as recently as 50,000 years ago? Well, as it turns out, this is precisely the situation with the diminutive Homo floresiensis from Flores in eastern Indonesia, most recently dated between 60,000 and 100,000 years old. Again, while the Hobbit might have prepared us philosophically for yet more radical discoveries, the case for Homo luzonensis needs to be judged solely on its merits. I think I’d prefer to leave the fossil in what Kenyan archaeologist and anthropologist Louis Leakey used to call the “ suspense account” until we have a lot more evidence. Dating the fossil finds The thing that bugs me the most about the new research is the seemingly poor understanding of the age of Homo luzonensis. There’s not much new evidence presented here about the dating of the site or the fossils themselves, and the work that has been done previously needs to be interpreted with a good deal of caution. The method used to date the actual fossils (called Uranium-series or U/Th Dating) can be notoriously unreliable when dating bones and teeth, and frankly, some of my colleaguessimply don’t accept that it’s up to the task. This is because bones and teeth can lose old uranium or take up new uranium when buried in sediments, like those contained in a cave, and there’s no way of really knowing if this has happened in the past. The method assumes that uranium was taken up just once in the past and then decayed giving us a radioactive clock but this is probably not the case in reality. It would be usual practice to check the dating of a site with different methods and using various materials (charcoal, sediment, bone, cave flowstone, and so on) and there’s no explanation provided why this hasn’t been done for Callao Cave and Homo luzonensis, or if it has, how the crosschecks compared? I think the best we can say is that the fossils would seem to be older than 50,000 years, but just how much older is anyone’s guess. They could be 55,000 years old or 550,000 years old, and this would make a very real difference in terms of their importance and place in human evolution. Still, if Détroit and his team are right about Homo luzonensis, the new discovery would add to a growing picture of extinct human diversity in Southeast Asia, which we simply couldn’t have imagined a decade or two ago. This article was originally published on The Conversation. Read the original article.<doc-sep>
ABOVE: Teeth of the newly named hominin Homo luzonensis CALLAO CAVE ARCHAEOLOGY PROJECT In 2007, archaeologist Armand Salvador Mijares found a curious bone buried in Callao Cave in the Philippine island of Luzon. Shortly after, he and his colleagues concluded it was a third metatarsal from a human that lived some 67,000 years ago. Together with other findings, it demonstrated that humans could cross the open ocean and reach isolated islands very early on in our history. But whether that bone belonged to Homo sapiens or another species of our genus was a mystery. Mijares, of the University of the Philippines, and his colleagues have since discovered twelve additional bones and teeth from the same site. Their analysis has revealed that the remains are unlike any other hominin fossils known, and likely represent a distinct species of the Homo genus. The researchers named it Homo luzonensis, they report today (April 10) in Nature. “It’s fantastic news. It’s not every day you get to name a new species within the human family tree,” remarks Michael Petraglia, a professor of human evolution and prehistory at the Max Planck Institute for the Science of Human History who wasn’t involved in the study. “The work is very strong, very robust, and they have convinced me that we’re probably looking at a new species within our genus.” Altogether, the team—a group of French and Australian researchers, as well as Mijares himself—found a partial femur, two hand phalanges, two feet phalanges, and seven teeth, from at least three individuals. They dated one of the molars to a minimum age of 50,000 years, slightly younger than the metatarsal. They weren’t able to extract any DNA from the fossils, making it impossible to conduct phylogenetic analyses. Instead they base their conclusions on detailed examination of the remains, using a range of techniques including traditional measurements, micro CT scans, and 3-D morphometric analyses. Two premolar and three molar teeth proved especially useful because they stemmed from the same individual. The molars had modern features reminiscent of H. sapiens and Asian H. erectus teeth, but they were too small to have stemmed from H. sapiens individuals. The premolars, on the other hand, could have stemmed from H. sapiens if one only considered their size. But these also had two or three roots—a characteristic regarded as primitive. These unique combinations of characteristics weren’t present in any known hominin fossils, explains Florent Détroit, a paleoanthropologist at the Muséum National d’Histoire Naturelle in Paris and a coauthor on the new study. The hand and foot phalanges puzzled the researchers, as some of them strikingly resembled those of an Australopithecus species, a hominin known from the African fossil record that lived up until 1.5 million years ago. “If we told people that we discovered them in Ethiopia in layers dated to 3 million years ago, everybody would agree with us [that] it’s really Australopithecus,” Détroit remarks. But to see such specimens in the Philippines from only 50,000 years ago is unexpected. The morphologies of Australopithecus hand and feet bones are thought to reflect varying degrees of climbing behavior or bipedalism, but it’s not yet clear how H. luzonensis may have moved, he adds. To Détroit, the findings suggest that isolation on islands can drive speciation in humans in the same way it does for other vertebrate species. “I’m almost a hundred percent sure that [the unique combination of features] we are observing in H. luzonensis is also due to the effects of insular endemism,” he says. Fossil excavation site in Callao Cave in northern Luzon in the Philippines CALLAO CAVE ARCHAEOLOGY PROJECT The Callao Cave fossils aren’t the earliest evidence of humans on Luzon: In 2018, researchers found a set of stone tools beside the remains of a butchered rhinoceros, just 20 kilometers away from the cave. They estimated these were around 709,000 years old. That would be enough time to evolve the unique characteristics the team observed in H. luzonensis, Détroit says, but it’s not clear if H. luzonensis descended from those early hominins. Some researchers question whether the evidence is enough to warrant a new species designation. “I think it is a really interesting set of remains, but it’s really at the lower end of the amount of evidence that you would want to base a new species on,” says Bernard Wood, a professor who studies human origins at George Washington University and wasn’t involved in the study. There could be other explanations for the unique combination of tooth features, he says.