Oldest animal fossils may be in Canadian rocks

A Canadian geologist may have found the earliest fossil record of animal life on Earth, according to a report published in the journal Nature. Around a billion years ago, a region of northwest Canada now defined by steep mountains was a prehistoric marine environment where the remains of ancient sponges may be preserved in mineral sediment, the paper says. Geologist Elizabeth Turner discovered the rocks in a remote region of the Northwest Territories accessible only by helicopter, where she has been excavating since the 1980s. Thin sections of rock contain three-dimensional structures that resemble modern sponge skeletons. The dating of adjacent rock layers indicates the samples are about 890 million years old, which would make them about 350 million years older than the oldest undisputed sponge fossils previously found. Many scientists believe the first animal groups included soft sponges or sponge-like creatures that lack muscles and nerves but have other features of simple animals, including cells with differentiated functions and sperm. Scientists believe life on Earth emerged around 3.7 billion years ago. The earliest animals appeared much later, but exactly when is still debated. Until now, the oldest undisputed fossil sponges date to around 540 million years ago, an era called the Cambrian period. This would be the first time that a sponge fossil has been found from before the Cambrian, and not only before, but way before – that’s what’s most exciting. The dating of 890 million years ago is significant because, if the sponge’s identification is confirmed, it shows that the first animals evolved before a time when oxygen in the atmosphere and ocean reached a level scientists once thought was necessary for animal life. Yet recent research shows that some sponges can survive with very little oxygen.