BBC Focus Magazine

[Shadowwolf]

Evidence of the single-celled ancestors of animals, dating from the interval in Earth's history just before multicellular animals appeared, has been discovered in 570 million-year-old rocks from South China by researchers from the University of Bristol, the Swedish Museum of Natural History, the Paul Scherrer Institut and the Chinese Academy of Geological Sciences.

All life evolved from a single-celled universal common ancestor, and at various times in Earth history, single-celled organisms threw their lot in with each other to become larger and multicellular, resulting, for instance, in the riotous diversity of animals. However, fossil evidence of these major evolutionary transitions is extremely rare.

http://www.sciencedaily.com/releases/2011/12/111222142444.htm