the earliest critters

Scientists may have discovered traces of the eldest ancestors of contemporary animals: spongy goo fossilized in stone.

The previous oldest animal fossils date from "only" 650 million years ago, although "molecular clocks" based on rates of genetic divergence indicate that animals should have originated about 850 million years ago. The new findings may therefore help solve the problem of the 250 million-year-gap.

Palaeontologists have looked long and hard for traces left by the first multi-celled organisms, fully aware that the soft-bodies might have left very few fossils.

The breakthrough came when Elizabeth Turner, of Laurentian University in Sudbury, Ontario, spotted odd patterns in the rocks of 850-million-year-old limestone reefs in the Mackenzie Mountains of Canada's Northwestern territory, and has spent the last 15 years, with Fritz Neuweiler of University Laval in Quebec, trying to deduce their origin.

Now Turner and Neuweiler, along with David Burdige of Old Dominion University in Virginia, have shown that the patterns match the distinctive textures found in reefs built by sponges.

As all science goes, these findings are tentative, subject to further theorizing. And, as always, read the whole thing.