Evolutionary History(3):

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• Estimates from molecular clock data suggest that the ancestors of the animals diverged from the ancestors of the fungi about 1 billion years ago
• Other studies say that the common ancestor of living animals may have lived sometime between 675 and 875 million years ago
• The first accepted fossils of animals range from 565 to 550 million years old: these fossils are members of an early group of multicellular eukaryotes, collectively known as the Ediacaran biota
• Neoproterozoic rocks have also yielded microscopic signs of early animals
• Animal diversification appears to have accelerated dramatically from 535- 525 million years ago, during the Cambrian period of the Paleozoic era [Cambrian explosion]