spontaneous generation

Erroneous belief that living organisms can arise spontaneously from nonliving matter. This idea survived until the mid-19th century, when the French chemist Louis Pasteur demonstrated that a nutrient broth would not generate micro-organisms if it was adequately sterilized. The theory of biogenesis holds that spontaneous generation cannot now occur; it is thought, however, to have played an essential role in the origin of life on Earth 4 billion years ago.