Around 541 million years ago, the diversity of life on our planet suddenly exploded. This period is known as the Cambrian explosion, and it lasted for 13-25 million years. It is said that fossil records of major animal phyla first appeared in this time period. Recent research, however, suggests that there could have been animals older than those in the Cambrian explosion. This research has found what seems to be sponge fossils that are 890 million years old, about 350 million years older than the animals of the Cambrian period.
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The ancient discovery is igniting debate among palaeontologists, who have long contested when complex animal life first evolved.
“If I’m right, animals emerged long, long before the first appearance of traditional animal fossils,” says study author Elizabeth Turner, a sedimentary geologist at Laurentian University in Sudbury, Canada. “That would mean there’s a deep back history of animals that just didn’t get preserved very well.”
However, some scientists, like geoscientist and fossil reef specialist Rachel Wood, argue the validity of Turner’s suggestion, saying that “It’s such a big claim that you really have to eliminate all the other possibilities.”
Sometimes crystals also grow in a way that looks like patterns formed by living organisms, she says, meaning that the rock samples Turner found might not be fossils at all.
Turner, however, argues that there are no known reef-building organisms that existed 890 million years ago. Other scientists see the possibility of Turner’s claim.
Whatever the case, Turner’s research creates a stir in the debate about the age of animal life here on Earth.
More about this over at Nature.
(Image Credit: Elizabeth C. Turner)