The origin of life on Earth is a controversial topic in the natural sciences. The current widely-accepted scientific theory about the origins of life on Earth is known as the nebular hypothesis, or simply out of equilibrium chemistry.
Perhaps the most fundamental and at the same time the least understood biological problem is the origin of life.
It is central to many scientific and philosophical problems and to any consideration of extraterrestrial life. Most of the hypotheses of the origin of life will fall into one of four categories:
- The origin of life is a result of a supernatural event—that is, one irretrievably beyond the descriptive powers of physics, chemistry, and other science.
- Life, particularly simple forms, spontaneously and readily arises from nonliving matter in short periods of time, today as in the past.
- Life is coeternal with matter and has no beginning; life arrived on Earth at the time of Earth’s origin or shortly thereafter.
- Life arose on the early Earth by a series of progressive chemical reactions. Such reactions may have been likely or may have required one or more highly improbable chemical events.
