Chinese mining operations at the Weng'an fossil site threaten to obliterate 600-million-year-old rocks. (ZHU Maoyan)
BEIJING—Paleontologists have argued for years about the identity of the enigmatic curling shapes and embryolike spheres found in the 600-million-year-old rocks of the Doushantuo Formation in China. But some say those fossils, no bigger than a grain of salt, may be the remains of some of the world's first animals. Now researchers fear that the rock formation may be pulverized, along with its cargo of fossils, before scientists can identify the creatures and what they may reveal about the evolution of animals. A massive phosphate mining operation in southern China threatens the site, and scientists are urging the Chinese government to step in to protect it.
The mining operations, which produce raw material for fertilizer, are already destroying unique fossil evidence at a distressing rate, says Zhu Maoyan, fossil expert and professor at the Nanjing Institute of Geology and Palaeontology in China. The site, with its mysterious Weng'an biota, is located in rural Guizhou, a Chinese province bordering Vietnam. Piecemeal phosphate mining has taken place there for years, but a large-scale project that began in 2015 could wipe out the entire site, including a wealth of as-yet-undiscovered fossils—a "disaster [to] all human beings," Zhu says. The mining project already has demolished one of the three key fossil sites, he says.
"If you want to know about how animals evolved on Earth, this site is the most important one we know of," says David Bottjer, earth sciences professor at the University of Southern California in Los Angeles, who has been visiting the Weng'an site to collect fossils since 1999, a year aftertheir discovery. "If this fossil deposit is lost, we will lose this unique window on evolution of life, which may never be replaced."
Weng'an fossils—putative embryos and occasional adults—lived 30 million years before the oldest widely accepted animals: the Ediacaran biota found in Newfoundland, Canada, and other sites. Those sea creatures, which come in an array of bewildering shapes, represent a lost era of life on Earth: They were later replaced during the Cambrian Explosion, when animals with more familiar body plans burst onto the scene. As precursors to the Ediacara, the Doushantuo fossils "provide an unparalleled window into the early evolution of lineages leading to animals and possibly [the evolution of] animals themselves," says Douglas Erwin, a paleobiologist at the Smithsonian Museum of Natural History in Washington, D.C.
This tiny tubular creature, only half a millimeter across, was unearthed at the Weng'an site and may be the world's oldest sponge.
The phosphate coveted by miners also helped preserve the ancient fossils. Bottjer explains that after the organisms died, phosphate replaced their tissues cell by cell, yielding exquisite soft-body preservation at tiny scales. "With a focus on the embryos, we have been able to learn a lot about the developmental process for early animals," he says. "We are just beginning to understand fossils of adult animals, which are also found but which are much rarer than the embryos."
Some scientists still maintain that the spheres and other forms represent not animals but some kind of precursor, as a paper last month in theJournal of the Geological Society argued. But a 2015 study in the journalEvolutionidentified an unusually well-preserved fossil as most likely being the world's oldest known sponge.
Regardless of the dispute, says Zhu, "the majority of the science community considers Weng'an's fossils invaluable" for deciphering the origins of animals. He led a group of concerned international scientists, including Erwin and Bottjer, to meet with government officials earlier this month to appeal for curbs on the mining. Officials at all levels of government, from local to national, listened to the scientists' concerns.
The officials must balance that plea against local interests: The phosphate and fertilizer industry is the pillar of the local economy, supplying 60% of total revenue to the Weng'an county government, according to one account in Chinese media. But after the meeting, Zhu says, officials took incremental steps to protect the fossils, halting mining "in the parts of the site that are most likely to hold fossils and the most vulnerable to being dug out." He says he believes that the government is beginning to understand the global significance of the Weng'an biota and hopes that they will act to stop mining permanently.