THE FORGOTTEN CONTINENT Fossil Finds in China Are Challenging Ideas About the Evolution of Modern Humans and Our Closest Relatives
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NEWS FEATURE THE FORGOTTEN CONTINENT Fossil finds in China are challenging ideas about the evolution of modern humans and our closest relatives. n the outskirts of Beijing, a small BY JANE QIU government is setting up a US$1.1-million limestone mountain named Dragon laboratory at the IVPP to extract and sequence Bone Hill rises above the surround- spread around the globe — and relegated Asia ancient DNA. Oing sprawl. Along the northern side, a path to a kind of evolutionary cul-de-sac. The investment comes at a time when palaeo- leads up to some fenced-off caves that draw But the tale of Peking Man has haunted anthropologists across the globe are starting to DEAGOSTINI/GETTY 150,000 visitors each year, from schoolchildren generations of Chinese researchers, who have pay more attention to Asian fossils and how to grey-haired pensioners. It was here, in 1929, struggled to understand its relationship to they relate to other early hominins — creatures that researchers discovered a nearly complete modern humans. “It’s a story without an end- that are more closely related to humans than ancient skull that they determined was roughly ing,” says Wu Xinzhi, a palaeontologist at the to chimps. Finds in China and other parts of half a million years old. Dubbed Peking Man, Chinese Academy of Sciences’ Institute of Ver- Asia have made it clear that a dazzling variety of it was among the earliest human remains ever tebrate Paleontology and Paleoanthropology Homo species once roamed the continent. And uncovered, and it helped to convince many (IVPP) in Beijing. They wonder whether the they are challenging conventional ideas about researchers that humanity first evolved in Asia. descendants of Peking Man and fellow members the evolutionary history of humanity. Since then, the central importance of Peking of the species Homo erectus died out or evolved “Many Western scientists tend to see Asian Man has faded. Although modern dating into a more modern species, and whether they fossils and artefacts through the prism of what methods put the fossil even earlier — at up to contributed to the gene pool of China today. was happening in Africa and Europe,” says 780,000 years old — the specimen has been Keen to get to the bottom of its people’s Wu. Those other continents have historically eclipsed by discoveries in Africa that have ancestry, China has in the past decade stepped drawn more attention in studies of human evo- yielded much older remains of ancient human up its efforts to uncover evidence of early lution because of the antiquity of fossil finds relatives. Such finds have cemented Africa’s sta- humans across the country. It is reanalysing there, and because they are closer to major tus as the cradle of humanity — the place from old fossil finds and pouring tens of millions palaeoanthropology research institutions, he which modern humans and their predecessors of dollars a year into excavations. And the says. “But it’s increasingly clear that many Asian 218 | NATURE | VOL 535 | 14 JULY ©20162016 Mac millan Publishers Li mited, part of Spri nger Nature. All ri ghts reserved. ©2016 Mac millan Publishers Li mited, part of Spri nger Nature. All ri ghts reserved. FEATURE NEWS The reconstructed materials cannot fit knows what they are because they don’t seem want everything to come from China.” skull of Peking Man, into the traditional to fit into any categories we know.” Chinese researchers reject such allegations. the fossil that launched narrative of human The fossils’ transitional characteristics have “This has nothing to do with nationalism,” says discussions of human evolution.” prompted researchers such as Stringer to Wu. It’s all about the evidence — the transitional origins in China. Chris Stringer, lump them with H. heidelbergensis. Because fossils and archaeological artefacts, he says. a palaeoanthro- the oldest of these forms, two skulls uncov- “Everything points to continuous evolution in pologist at the Natural History Museum in ered in Yunxian in Hubei province, date back China from H. erectus to modern human.” London, agrees. “Asia has been a forgotten 900,000 years1,2, Stringer even suggests that But the continuity-with-hybridization model continent,” he says. “Its role in human evolu- H. heidelbergensis might have originated in is countered by overwhelming genetic data tion may have been largely under-appreciated.” Asia and then spread to other continents. that point to Africa as the wellspring of mod- But many researchers, including most ern humans. Studies of Chinese populations EVOLVING STORY Chinese palaeontologists, contend that the show that 97.4% of their genetic make-up is In its typical form, the story of Homo sapiens materials from China are different from Euro- from ancestral modern humans from Africa, starts in Africa. The exact details vary from one pean and African H. heidelbergensis fossils, with the rest coming from extinct forms such telling to another, but the key characters and despite some apparent similarities. One nearly as Neanderthals and Denisovans5. “If there had events generally remain the same. And the title complete skull unearthed at Dali in Shaanxi been significant contributions from Chinese is always ‘Out of Africa’. province and dated to 250,000 years ago, has H. erectus, they would show up in the genetic In this standard view of human evolu- a bigger braincase, a shorter face and a lower data,” says Li Hui, a population geneticist at tion, H. erectus first evolved there more cheekbone than most H. heidelbergensis speci- Fudan University in Shanghai. Wu counters that than 2 million years ago (see ‘Two routes for mens3, suggesting that the species was more the genetic contribution from archaic hominins human evolution’). Then, some time before advanced. in China could have been missed because no 600,000 years ago, it gave rise to a new spe- cies: Homo heidelbergensis, the oldest remains of which have been found in Ethiopia. About THE EVOLUTIONARY TALE IN ASIA IS MUCH MORE 400,000 years ago, some members of H. hei- INTERESTING THAN PEOPLE REALIZED. delbergensis left Africa and split into two branches: one ventured into the Middle East and Europe, where it evolved into Neander- Such transitional forms persisted for DNA has yet been recovered from them. thals; the other went east, where members hundreds of thousands of years in China, Many researchers say that there are ways became Denisovans — a group first discov- until species appeared with such modern traits to explain the existing Asian fossils without ered in Siberia in 2010. The remaining popu- that some researchers have classified them as resorting to continuity with hybridization. lation of H. heidelbergensis in Africa eventually H. sapiens. One of the most recent of these is The Zhirendong hominins, for instance, could evolved into our own species, H. sapiens, about represented by two teeth and a lower jawbone, represent an exodus of early modern humans 200,000 years ago. Then these early humans dating to about 100,000 years ago, unearthed from Africa between 120,000 and 80,000 years expanded their range to Eurasia 60,000 years in 2007 by IVPP palaeoanthropologist Liu Wu ago. Instead of remaining in the Levant in the ago, where they replaced local hominins with and his colleagues4. Discovered in Zhirendong, Middle East, as was thought previously, these a minuscule amount of interbreeding. a cave in Guangxi province, the jaw has a clas- people could have expanded into east Asia, A hallmark of H. heidelbergensis — the sic modern-human appearance, but retains says Michael Petraglia, an archaeologist at the potential common ancestor of Neanderthals, some archaic features of Peking Man, such as University of Oxford, UK. Denisovans and modern humans — is that a more robust build and a less-protruding chin. Other evidence backs up this hypothesis: individuals have a mixture of primitive and Most Chinese palaeontologists — and a few excavations at a cave in Daoxian in China’s modern features. Like more archaic lineages, ardent supporters from the West — think that Hunan province have yielded 47 fossil teeth H. heidelbergensis has a massive brow ridge and the transitional fossils are evidence that Peking so modern-looking that they could have no chin. But it also resembles H. sapiens, with Man was an ancestor of modern Asian people. come from the mouths of people today. But its smaller teeth and bigger braincase. Most In this model, known as multiregionalism the fossils are at least 80,000 years old, and per- researchers have viewed H. heidelbergensis — or continuity with hybridization, hominins haps 120,000 years old, Liu and his colleagues or something similar — as a transitional form descended from H. erectus in Asia interbred reported last year6. “Those early migrants between H. erectus and H. sapiens. with incoming groups from Africa and other may have interbred with archaic populations Unfortunately, fossil evidence from this parts of Eurasia, and their progeny gave rise to along the way or in Asia, which could explain period, the dawn of the human race, is scarce the ancestors of modern east Asians, says Wu. Zhirendong people’s primitive traits,” says and often ambiguous. It is the least under- Support for this idea also comes from arte- Petraglia. stood episode in human evolution, says Russell facts in China. In Europe and Africa, stone Another possibility is that some of the Ciochon, a palaeoanthropologist at the Univer- tools changed markedly over time, but homi- Chinese fossils, including the Dali skull, rep- sity of Iowa in Iowa City. “But it’s central to our nins in China used the same type of simple resent the mysterious Denisovans, a species understanding of humanity’s ultimate origin.” stone instruments from about 1.7 million years identified from Siberian fossils that are more The tale is further muddled by Chinese fossils ago to 10,000 years ago.