Chinese Trilobites - Mountains & Mole Hills
Professor Hou Xianguang (in background, in white shirt) with crew recruited from local villages
According to the latest scientific data, there are now more than 40 geological locations throughout the world that have revealed themselves to be the cradles of early life. These are outposts where the fossil evidence is of just the right age and state of preservation to provide a unique view of what primitive fauna was like in the oceans soon after complex forms began their dizzying trek through evolutionary time. Some of these Cambrian sites provide only tantalizing clues of what these early forms may have looked like -- usually disarticulated pieces of trilobites with their hard shells, well-developed crescent-shaped eyes and an exotic array of species. But other localities reveal more… much more. In these special spots, not only have the remnants of complete trilobites been preserved in the finely-grained sedimentary deposits, but so have the fossilized impressions of a wide array of soft-bodied creatures.
The most famous of these captured-in-time locales is unquestionably the 510 million year-old Middle Cambrian Burgess Shale in British Columbia, Canada, perhaps the most studied, lauded and legendary invertebrate outcropping on Earth. A similar, slightly older but less prolific Cambrian biota featuring primitive soft-bodied fossils as well as an array of early trilobites can be found off the coast of South Australia in the Emu Bay Shale. Here creatures similar to those found at the Burgess site appear to mingle with many totally unique life forms.
Another intriguing locale lies in the American southwest, where amid the renowned Middle Cambrian trilobite strata of Utah, a wide variety of soft-bodied fossils have been revealed, with many being biologically contiguous with those found in similar exposures throughout the globe. Despite the legendary status of Burgess, however, and the more current paleontological renown provided by the material from Utah and Australia, there is one formation on earth that features an even older fossil bearing strata. Indeed, this location may represent the earliest look we've yet had at the amazingly diverse fauna that first filled our primitive seas.
Deep in the heart of the vast Asian continent, sequestered within the rolling hills and tree-lined valleys that define much of China's Yunnan province, lies the Lower Cambrian Chengjaing Biota, a series of 515 million year old formations that together form one of the most important fossil sites in the world. In this rather isolated wilderness not far from the border of Viet Nam, some of the oldest known soft-bodied arthropods on earth have been found, animals that predate the more illustrious material from the Burgess Shale by more than 5 million years. These are strange creatures, with equally intriguing names such as Hallucigenia and Microdyction, which have begun to provide paleontologists with a unique window onto the initial tentative steps that life took on this planet during a time that has become popularly known as the Cambrian Explosion.
While the vast majority of the 185 species (with more than half being arthropods) that have so-far been found within Chenjiang's Maotaishan shales apparently led to evolutionary dead ends, others possibly did not. With the formation featuring an impressive array of sponges, worms and echinoderms as well as a variety of arthropods, the strata presents one of the most diverse Lower Cambrian biota ever found. The shales' impressive arthropod assemblage includes four trilobite species, Eoredlichia intermedia, Yunnanocephalus yunnanensis, Wutingaspis tingi and Kuanyangia pustulosa, along with the cosmopolitan “trilobite-eater” Anomalocaris, whose fossilized remains have also been discovered in Canada and Australia as well as in the western United States. And perhaps most significantly, among the formation's array of fossils featuring soft body part detail, there is evidence of the first chordates, animals with what clearly appear to be primitive backbones -- creatures that in some currently unimaginable way may have stood at the foundation of an evolutionary line that led very indirectly to humans… more than 500 million years in the future.
“We've grown to understand a great deal about early life thanks to a century's worth of study of Burgess material,” said Fred Collier, formerly of Harvard's Museum of Comparative Zoology. “But the arrival of fossils from other locations (such as Chenjiang) have supported some of our previous thoughts, while turning others upside down.”
The Chengjiang Biota is situated some 1,500 miles southwest of China's cultural, political and spiritual center in Beijing, yet Yunnan Province as a whole might as well be a million miles away in terms of its grasp upon the 21st Century. The still-often-oppressive reach of China's central government rarely touches here, and life in and around the area remains much as it might have been 100, 200 or even 500 years ago. The main means of transportation is by oxcart and for most local residents such “conveniences” as electricity and indoor plumbing are as alien as an I-pad. Despite the distinctly backward appearance that many parts of Yunnan Province can convey to Western eyes, however, the area's inhabitants are uniformly curious about the world around them.
Rather than battling against any perceived threat posed by modern technology, when given the opportunity those who live in-and-around Chengjiang do their best to embrace it. Even when geologists first visited the Yunnan region in the late '70s looking for a quick way to tap into the area's rich phosphate deposits, the interest shown by the locals was immediate and overwhelming. After all, they had been digging in the nearby hills, utilizing its resources as well as finding strange “shapes” in the rocks, since the 10th Century. By sheer good fortune those phosphate deposits happened to lay directly above and below the thick fossil bearing layers of the Maotaishan shales, and led somewhat unintentionally to the discovery of the area's now-renowned Lower Cambrian fossils.
Without great prompting or the promise of financial gain, locals have always been eager to impart as much information as they could about their home territory, and in the process of doing so, absorb whatever new knowledge was to be provided by the visiting academics. What these residents wanted to know more than anything else was simple -- what was interesting enough about the craggy cliffs that had surrounded them their entire lives to draw scientists to their remote corner of the globe? But it wasn't until Chinese paleontologist Hou Xian-guang discovered the Chenjiang Biota in the early '80s that they -- and the rest of the scientific community -- began to fully learn the answer.
Almost immediately after the first exploratory paleontological work had begun in the area, these locals started to understand that something special had been found in their hills, and they were more than willing to do whatever they could to contribute to the visiting scientists' quest for discovery. Perhaps most didn't fully fathom that fossils more than half-a-billion years old were being uncovered, and that such discoveries would directly lead to a greater understanding of earth's distant past. But such facts seemed to matter little in terms of their interest and labor. Indeed, their efforts directed towards digging out and then breaking apart layer-upon-layer of sedimentary rock led directly to the eventual recovery of thousands of fossil specimens.
Yet, as is so often the case with scientific exploration in underdeveloped parts of the world, there is another side to this story -- one that questions where exploration ends and exploitation begins. The vast, 160 foot-thick strata of hard, yellow mudstone that comprise the Maotaishan shales may have initially appeared impervious to anything outside of an army of giant bulldozers and modern rock-moving machinery. Yet an “army” of another sort -- hordes of local residents spurred on by curiosity and the chance to earn a small wage by breaking rock and finding fossils -- has over the years, begun to turn the mountains that are Chengjiang into something more resembling proverbial mole hills.
During that time hundreds of metric tons of rock have been removed by hand. Yet the subsequent damage done to the area's topography has never been properly offset by the minimal benefits to the local economy brought forth by the fossil trade. After nearly two decades of uncontrolled digging at the site, the Chinese government slowly began to realize the inherent ecological dangers posed by the on-going work being conducted at Chengjiang. They then took immediate, drastic, and highly uncharacteristic measures to protect the site. In 2001, they placed the entire Maotaishan shale under the jurisdiction of a National Historical Park -- which immediately limited access to the area -- and legislation is currently being drawn to provide the site with a World Natural Heritage designation, intended to strictly control all excavations done throughout the vicinity.
“There is immediate need to save the entire formation,” a Chinese spokesperson stated. “We need to make sure that scientists have the opportunity to study everything important that is found at the site. The fossil exploration has done considerable damage, but the on-going phosphate mining -- which accounts for a great deal of the economic stability of the entire region -- has threatened the destruction of the entire formation. The change in landscape over the last three decades is astounding… and somewhat horrifying.”
Whether or not we choose to involve ourselves with the political issues that will soon seemingly control all fossil-related activities being conducted anywhere within China, the scientific importance of the material being found in Yunnan Province is beyond question. After all, Chengjiang may well prove to be the oldest site in the world featuring such an impressive array of primitive soft-bodied fossils, for it would seem difficult to imagine a more ancient or revealing Lower Cambrian strata. The fact is, however, that despite the antiquity and diversity of material found within the Maotaishan shales, it may still be possible for science to draw even closer to the root-stock of the explosion in life that began with the dawning of the Cambrian.
We do know of a far more ancient Precambrian fauna in Australia, where bacteria some 3.5 billion years old have been found, and 3.8 billion year old carbonized traces found in Greenland may be of organic forms. But it wasn't until late in the Precambrian -- during what is known as the Ediacaran era that began 600 million years ago -- that we begin to see indisputable signs of multi-cellular life… with the first remnants of hard-shelled organisms beginning to appear at the very end of this time period, approximately 540 million years ago.
Theories involving an increase, or even possibly a decrease, in the ocean's oxygen level, as well as au-courant postulations concerning a “Frozen Earth”-- where the entire planet was essentially trapped within an ice ball until shortly before the beginning of the Cambrian -- have all been presented by leading scientists in their attempts to explain why the planet suddenly burst forth with life soon after the dawning of the Paleozoic era. And while locations such as Chengjiang, Burgess and Emu Bay each present tantalizing clues as to why some of the most important changes in earth history took place over a relatively short period of geologic time, the simple fact is that we may never know the full answer to the most basic question we can ask: What triggered the emergence of multi-cellular life? But as more and more vital information pours forth from the hills of Southern China, and as more amazing discoveries are made and scientific analysis completed, it seems that we are slowly drawing ever-closer to understanding the essence of early life on Planet Earth.