A fossil smaller than a sesame seed has revealed the invisible early history of animals on Earth and could reconcile a major evolutionary paradox. Previous phylogenetic studies, which model the evolution of groups of related organisms, have suggested that the animals that gave rise to sea sponges, sea anemones, worms and crustaceans first appeared 600 million to 700 million years ago. But until now, scientists had no undisputed fossil evidence of any animals at all prior to about 575 million years ago.
展开▼
