Tuesday, February 1, 2011

HISTORY OF LIFE ON EARTH




The history of life on Earth began about 3.8 billion years ago, during the Achaean era, initially with single-celled prokaryotic cells, such as bacteria. Multi-cellular life evolved over a billion years later and it's only in the last 570 million years that the kind of life forms we are familiar with began to evolve, starting with arthropods, followed by fish 530 million years ago (Ma), land plants 475Ma and forests 385Ma. Mammals didn't evolve until 200Ma and our own species, Homo sapiens, only 200,000 years ago. So humans have been around for a mere 0.004% of the Earth's history.

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