Homo Longi's place in our family tree is not far away.
The reported discovery of a new species of hominin from China caused an uproar last week. Its discoverers - paleoanthropologists Shijun Ni, Qiang Jie, Chris Stringer and their colleagues - say the skull discovered near Harbin in northeastern China contains a range of features similar to those of Neanderthals, Denisovans and Homo sapiens. separate type. The researchers named the findings Homo longi, the river in which the skull was discovered. Based on a statistical comparison of cranial measurements with other human skulls, Nye and colleagues say that Human Longi is the sister lineage to Neanderthals, Denisuans, and us. p>
Based on its age in the uranium series, the Harbin skull has been buried for at least 146,000 years, but it looks pretty good. Fossil hominid skulls are often crushed or twisted after thousands of years on Earth due to their high ground weight, but the Harbin skull is by no means deformed. It is intact, even if the only tooth still attached is the left molar. This in itself is unusual, as teeth are usually the most common fossil finds of hominins.
The skull has a broad face with small, smooth cheekbones located just below the dome of the skull. The face does not protrude like Australopithecus or the modern ape in front of the skull, although the upper jaw is still slightly protruding. There are large eye cavities under the heavy curved edges of the eyebrow. It's as big as a modern person, but it's tall and short instead of tall and round. The jaw once contained a large molar that appears to have belonged to an older member of our family - or a Denisovan. Species such as Homo erectus and Homo heidelbergensis have long skull arches like the skull of Harbin. But they both have a bony protrusion on the back of their skull called the occipital lobe (or occipital lobe). The tall, low skulls and occipital lobes are usually signs of an ancient branch of the family tree: traits inherited from our last common ancestor with modern apes, not new traits where our paths diverge. Harbin's heavy brow spurs, a prominent upper jaw, and large, sturdy mill teeth are also ancient features.
Old and Modern
On the other hand, a relatively flat face that sits just below the eyebrows is characteristic of modern humans, not protruding from the front. The same applies to the lower and lower cheekbones of the skull and the large capacity of the skull (if you calculate it is about 1420 ml). Once again, Harbin's skull is pretty cool overall. As Nye and colleagues write, "its massive overall size distinguishes it from nearly any other fossil," so we cannot be certain that its largest material is larger than its body size. According to Ney et al. Even before Harbin's skull, anthropologists didn't see all of these features together in this exact mix. This is what paleontologists call a mosaic, some features appear to be from older lineages and others are similar to ours.
Mosaic is common in the family tree of hominins. But the important question about the Harbin skull is whether its blend of features really is a trademark of an entirely separate species, related to—but distinct from—Neanderthals, Denisuans, and us. Ancient human scientists have discovered many Neanderthal skulls, but the only Denisovan fossils known so far are a few teeth, a finger bone and a skull fragment from Denisova Cave in Siberia, as well as the Xia jawbone in northern China. In other words, if we want to say that it resembles a Denisovan skull, we do not have many examples to compare the lower jaw of Harbin. Of course there is nothing wrong with the Homo sapiens skull, and it is clear that the Harbin skull, wherever it may be, did not belong to a member of our species (spoiler warning: depending on our species' definition).
Looking at the skulls of modern humans, it should be noted that the difference in size, shape and appearance can be found in a species, especially the type that is adapted to live in different environments of the world. be. Harbin's skulls could be in the normal range of diversity for Denisoans, who were also a very broad species, or something completely different. We don't have enough information about the Denisuan skulls to be aware of.
Denisuan or Homo longi?
When Ni and his colleagues performed their statistical analysis, they noticed that Harbin's skull, along with a 160,000-year-old Denisovan, had fallen from his sheikhs in a group that anthropologists rely on. They identified the proteins that were still stored in it. In other words, Harbin and Xiae likely belong to one or more closely related species. Meanwhile, the molar still attached to Harbin's skull closely resembles the Denisovan's molar from Denisova Cave in Siberia. Harbin's skull was also found well with a 200,000-260,000-year-old skull in northwest China's Dali Province, a nearly 300,000-year-old skull was found in Hualong Cave in eastern China, and a skull with 260,000-year-old Jin Noshi Cave . (sometimes spelled Jiniushan) in China. All three of these fossils have been described as something similar to Homo erectus and Homo erectus.
It is possible—though still more speculative—all or some of these fossils, along with some fossils in Taiwan and northern China whose molars look very similar to Xia's, are possible. Is a group of Denisuan individuals in East Asia.
However, the Harbin skull is an important find. It need not represent an entirely new species in science to be a valuable part of an unwritten chapter of our evolutionary story. Denisovan remains are still extremely rare, and it is becoming increasingly clear that East Asia was an important place for our early and Middle Paleolithic ancestors.Advertising
Once again, at least some Asian hominid fossils may become distinct, Nick and colleagues claim. Only other evidence can clarify this argument, and Ni and colleagues confirm this in a recent article. "More jaw samples from the Harbin population, or the mandibular proximal skull samples, test the morphological affinity of the Harbin and proximal humans," they wrote, while the new genetic material tests the relationship of these populations to each other and to Denisuans. "
Testing for DNA, proteins, and other evidence
provides the clearest answer. At one time, biologists would classify species and their relationships based on this" Now, this question often goes back to genetics . Of course, for many older hominin species, this is impossible. No Australopithecus or the original human DNA has survived, so anthropologists look like bones. "But we have the genomes of Neanderthals, Denisuans, and of course Homo sapiens, and if ancient DNA can be recovered from Harbin's skull, most of the controversy can be resolved.
Even without DNA, there is another option. Genes are encoded in DNA. For proteins, which are the building blocks of an organism and proteins may live longer than DNA in ancient bones.In 2019, Ford anthropologist Fordow Volker told Ars Technica Proteom, analyzing Chia as a Denisovan could be the key to discovering more Of Denisoan fossils previously unearthed in museums, he said. They sit. Of course, the best examples of ancient DNA in the world do not solve the more complex problem of how to identify a species from Type I - a controversy that Homo Langi directly entered.
Spacers, Bulbs, and Joint Fitness
Even by comparing entire genomes, scientists do not always agree on species, subspecies, or only diverse groups. Classically, if two organisms cannot be mixed together, they are considered two We are separated We know that Neanderthals, Denisuans, and Homo sapiens linked most of the Early and Middle Paleolithic to several continents, and the evidence is still in our genes. As expected, some anthropologists argue that if we were to call them different at all, we would call the Neanderthal and Denisovan subspecies of Homo sapiens.
According to the ancient anthropologist John Hawkes, when individuals of different types have hybrid babies, the offspring usually do not have a good chance of reproducing. Some hybrids, such as mules, are sterile, while others may face other challenges. Hawkes told Arras that levels of Neanderthal and Denisoan DNA in the modern genome "suggest that hybrids in this lineage were common and successful in humans. That's what we would expect if they hadn't spied." Others argue that there are enough genetic and physical differences between the three groups to consider them as separate species. A comparison of the Denisovan genome recovered from a fossil fragment in Denisova Cave and fragments of Denisovan DNA in the modern human genome shows that they were two distinct groups that were separated about 300,000 years ago. This means that they "could therefore be nearly as different as Neanderthals from Denisovans," anthropologist Jean-Jacques Hublin of the Max Planck Institute for Evolutionary Anthropology told Ars in 2019. (An analysis of the genomes of Neanderthals and Denisovans shows that the two sister species differed between 445,000 and 473,000 years ago.)
If Neanderthals and Denisovans were considered two separate species, should what we call Denisovans be two or three separate species? Ironically, this may be the best argument in favor of the human langi as a new species.
So where does Homo longi leave? It's hard to say until we have more evidence. And the new evidence is likely to determine where the debate really begins.
Innovation, 2021 DOI: 10.1016/j.xinn.2021.100130 (about DOI).
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