biogenesis

Biogenesis is the principle that living organisms arise only from preexisting living organisms. It contrasts with the ancient notion of spontaneous generation and is a foundational concept in modern biology, reinforced by the cell theory, which holds that new cells are produced by division of existing cells.

Historically, arguments for biogenesis gained support through controlled experiments in the 17th–19th centuries. Francesco Redi demonstrated that maggots on decaying meat came from fly eggs, not from the meat itself. Lazzaro Spallanzani showed that boiled broths remained sterile when sealed from the air, and Louis Pasteur’s swan-neck flask experiments provided strong evidence that microorganisms originate in the environment rather than spontaneously forming in broth. These findings helped discard spontaneous generation as a general explanation for the origin of life.

In contemporary biology, biogenesis describes the reproduction and propagation of life, including cellular division (such as mitosis and meiosis) and various modes of reproduction (asexual and sexual). It underpins germ theory, heredity, and the persistence of biological lineages across generations.

In the study of life's origins, the related concept of abiogenesis refers to how nonliving matter could give rise to simple life forms. Biogenesis, by contrast, asserts that once life exists, its further reproduction and diversification occur through biological processes that operate within and among living organisms.