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The Precambrian dates from the beginning of Earth's formation (4.6 billion years ago) to the beginning of the Cambrian Period, 542 million years ago. The Precambrian consists of the Hadean, Archaean and Proterozoic eons. Specifically, this article examines the Ediacaran, when the first multicellular bodies are believed to have arisen, as well as what caused the rise of multicellularity. This time period arose after the Snowball Earth of the mid Neoproterozoic. The "Snowball Earth" was a period of worldwide glaciation, which is believed to have served as a population bottleneck for the subsequent evolution of multicellular organisms.