Washington D.C. -- Researchers have discovered what appears to be evidence of worm-like animals in rocks that are over 1 billion years old--about twice as old as any other evidence for multicellular life yet discovered. These findings add a new perspective to the origination of multicellular animals, typically thought to have begun with a sudden explosion during the early Cambrian period, about 540 million years ago. The study will be published in the 2 October issue of Science.

Researchers from the University of Tbingen and Yale University, as well as Jadavpur University in Calcutta, have found tunnels that may be burrows left behind as ancient worm-like animals wriggled through sand beds underneath a shallow sea covering what is now Central India. These structures, known as "trace fossils," were preserved when the beds solidified into rock 1.1 billion years ago. Before this discovery, the oldest known fossil evidence of multicellular animals was 580 million years old.

The Cambrian is often thought to have been the "big bang" of animal evolution, a time when a wide variety of organisms originated and left their mark on the fossil record. An important argument for this model of evolution has been that no multicellular organisms have been found in rocks older than the Cambrian. However, some molecular studies have suggested that soft-bodied animals arose well before the Cambrian, perhaps as much as 1 billion years ago. The new findings, reported by Adolf Seilacher and his colleagues, add to the body of evidence suggesting that the diversification of animal designs experienced a "slow burn" before the Cambrian explosion.

The trace fossils are preserved in the Chorhat Sandstone, which contains sand beds that built up during storms. The tops of many sand beds were covered with a microbial mat that blanketed the floor periodically and protected the sand below from any disturbances
'"/>

Contact: Kathy Wren
kwren@aaas.org
(202) 326-6215
American Association for the Advancement of Science
30-Sep-1998