On the banks of the Danshui River in China, scientists have unearthed a treasure-trove of pristine fossil remnants from one of the most important periods in the history of life on Earth.
The big picture: The Cambrian explosion, which occurred a little more than 500 million years ago and lasted for about 40 million years, is the period when nearly all the major groups of multicellular life forms currently on Earth first appeared. It was a period of frenzied evolutionary development and biodiversity buildup, mainly in the world's oceans.
Why it matters: Understanding the creatures that came into existence at that time will improve scientists' knowledge of where animals alive today fit into the planet's evolutionary history, and it could help researchers better understand some of the most complex organisms, such as humans.
What they found: The newly analyzed Qingjiang fossil site yielded 4,351 specimens, and it is expected to contain many more. So far, 53% of them are new to science, according to the study published Thursday in the journal Science.
- “The authors of this study are going to have a huge job on their hands just describing these alone," Allison Daley of the University of Lausanne, who was not involved in the new research, tells Axios.
Like other Cambrian fossil sites, the majority of fossils are of soft-bodied creatures, including jellyfish and sea anemones, both of which exist close to the base of the animal family tree.
- “These fossils are among the best fossils I’ve ever seen in my career," Daley says, noting that fossils at the site include soft tissues, eyes and internal organs.
The new life forms that first showed up during the Cambrian explosion include creatures that are related to modern animals, but would be utterly unrecognizable if you came across them today.
- The site appears to have been located in an area that had environmental conditions that differ from other Cambrian fossil deposit sites.
Study co-author Robert Gaines of Pomona College says the Qingjiang site shows that differences among fossil assemblages can be traced to environmental conditions that influence ecosystem structure.
One cool thing: Many of the Cambrian creatures were truly bizarre looking.
- Many had 4 or 5 eyes.
- Some, like the Hallucigenia, had heads that closely resembled their tails and were characterized by spikes sticking out from their backs.
- Most invertebrates that emerged during this period were small — though there were some that went against this trend, like the Anomalocaris, or "abnormal shrimp," which measured 3 feet in length.
The bottom line: Gaines says a central lesson from the Cambrian explosion is that it takes a rare combination of ingredients to produce a tremendous diversity of life forms, and that once it exists, such biodiversity should be preserved.
- He adds, "[The findings] also remind us of our deep kinship to all living animals."