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Precambrian body plans
Until the late 1950’s, the Precambrian era was not believed to have hosted multicellular organisms. However, with radiometric dating techniques, it has been found that fossils initially found in the Ediacara Hills in Southern Australia date back to the late Precambrian era. These fossils are body impressions of organisms shaped like disks, fronds and some with ribbon patterns that were most likely tentacles.
These are the earliest multicellular organisms in Earth’s history, despite the fact that unicellularity had been around for a long time before that. The requirements for multicellularity were embedded in the genes of some of these cells, specifically choanoflagellates. These are thought to be the precursors for all multicellular organisms. They are highly related to sponges (Porifera), which are the simplest multicellular organisms.
In order to understand the transition to multicellularity during the Precambrian, it is important to look at the requirements for multicellularity—both biological and environmental.
==Precambrian era==
The Precambrian era, literally meaning "before life" dates from the beginning of Earth’s formation (4.6 billion years ago) to the beginning of the Cambrian era, 542 million years ago. The Precambrian consists of the Hadean, Archaean and Proterozoic Eons.〔 Specifically, this article will examine the Ediacaran, when the first multicellular bodies are believed to have arisen, as well as what caused the rise of muticellularity. 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.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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