Ask any paleontologist when the first animals appeared on Earth, and they will tell you the same thing: with a few notable exceptions, it was during the Cambrian eruption 541 million years ago. Okay, no paleobiologist. A new study published in the journal Nature is turning heads with a basic suggestion: sponges, one of the simplest creatures on the planet, maybe much older than the Cambrian eruption – 350 million years old, to be exact.
The Wiggly-looking structures in the rocks of northwestern Canada resemble the inner scales of sea sponges, but they are 890 million years old. If confirmed, they could be the oldest known animal fossils in the world. “If I’m right, the animals appeared long before the first fossils of traditional herbivores,” study author Elizabeth Turner told Nature. “It means the animal has a deep background history that just couldn’t be preserved very well.”
The idea that animal life existed before the Cambrian era is controversial, but not new. Paleontologists have two main resources that they can estimate when animals first appeared: fossil records and a technique called molecular clock estimation. The former is simple: if we find a fossil that is x million years old, that animal must have lived at that time.
The latter is more abstract: it is based on the idea that evolution occurs at a relatively constant speed, and therefore can be worked out by comparing how different the species are from each other since the time the two species shared a common ancestor. The problem arises when these two methods give radically different answers. Most estimates of the atomic clock tell us that the last common ancestor of animal life evolved today, the first 100 million years ago, shortly before the definitive fossil record was created.
Turner’s paper is “quite convincing” in that respect, according to paleontologist Amelia Penny, who was not involved in the study. He told New Scientist that this new hypothesis “brings back the fossil record with the atomic clock estimate.” Turner found the first 890 million-year-old rock specimens that eventually led him to his paper as a student, but this did not happen several years later, as a professor, he was able to return to Little Dal reefs in far northwestern Canada Go.