62.Origin of Earth dates back to A. 3500 million years ago B. 4500 million years ago C. 2900 million years ago D. 10,000-20,000 million years ago
Option B It is generally agreed that all life today evolved by common descent from a single primitive lifeform. We do not know how this early form came about, but scientists think it was a natural process which took place perhaps 3,900 million years ago. A scientific study from 2002 shows that geological formations of stromatolites 3.45 billion years old contain fossilized cyanobacteria. It is now widely agreed that stromatolites are oldest known life form on Earth which has left a record of its existence. Therefore, if life originated on Earth, this happened sometime between 4.4 billion years ago, when water vapor first liquefied and 3.5 billion years ago.
