No one knows exactly how life originated on Earth. The planet is approximately 4.6 billion years old. Fossils of microorganisms similar to blue-green bacteria are present in rocks three billion years old. This suggests that life evolved within the first billion years after the Earth was formed, at a time when the planet's environments were very different from those of today. Experiments performed over the past 50 years suggest that many important ingredients of organisms, including amino acids and nucleic acids, may have formed under pre-life conditions existing on Earth; their presence must have facilitated the actual genesis of the first organisms.

Background of the origin of life

All organisms are made of chemicals rich in the same kinds of organic, or carbon-containing compounds. Moreover, the same 20 amino acids combine to make up the enormous diversity of proteins occurring in living things. In addition, all organisms...