Origin and Evolution of life on Earth

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When Earth was born around 4.6 million years ago, the geological conditions for life to exist on it were very adverse. When the meteoritic bombardments ended and planet cooled, its surface solidified into a crust, the then proto-continents, which grew for some 2.5 billion years to form present size continents

The history of life on Earth began about 3.8 billion years ago, initially with single-celled prokaryotic cells, such as bacteria. Multicellular life evolved over a billion years later.

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.

Author: Dr Devleena Mani Tiwari, UGC-Assistant Professor, Centre for Earth, Ocean and Atmospheric Sciences, University of Hyderabad.

Posted By : ScienceIndia Administrator