THE ancestors of major animal groups may have existed 700 million years
earlier than biologists realised.
The fossil record suggests an 鈥渆xplosion鈥� of animal life 530 million years
ago, when many groups appeared. But a team led by Blair Hedges of Pennsylvania
State University has traced the origins of nematode worms to 1.2 billion years
ago (Proceedings of the Royal Society of London B, vol 266, p 163).