The Origin and Early Evolution of Life

Terrestrial life emerged in a murky and violent period of history that has left little trace of its existence. Astrobiologists have been left to infer its likely origins from what meager and indirect evidence nature has left for us to decipher. We know, for example, that one of the building blocks of cells—a group of chemicals called amino acids—are found in the nebulae from which planets condense. Amino acids are also ubiquitous in a class of meteorites called carbonaceous chondrites. These observations imply that they could have been delivered to Earth very early in its history, but it does not say that they were.