Experiments in support and against Spontaneous Generation


The doctrine of spontaneous generation was a widely accepted scientific theory that held that living creatures could arise from nonliving matter and that such processes were commonplace and regular . It was based on the observation of various phenomena that seemed to support the idea that life could emerge from inanimate material, such as dust, mud, or decaying flesh. For example, some people believed that mice could be generated from rags and wheat kernels, or that maggots could appear on rotting meat.

The theory of spontaneous generation was coherently synthesized by the Greek philosopher and naturalist Aristotle (384–322 BC), who compiled and expanded the work of earlier natural philosophers and the various ancient explanations for the appearance of organisms. Aristotle proposed that life arose from nonliving material if the material contained pneuma (“vital heat”) . He also classified living beings into two types: those that are generated from seeds (such as plants and animals), and those that are generated spontaneously (such as insects and worms). He explained the latter type by suggesting that some parts of the earth had a natural tendency to produce life, and that different kinds of living things could arise from different kinds of substrates. For instance, he claimed that seashells were spontaneously generated from slime, sand, or rocks, depending on the nature of the seabed.

Aristotle`s theory of spontaneous generation was influential and widely accepted for two millennia. It was not until the 17th and 18th centuries that it was challenged by the experiments of Francesco Redi and Lazzaro Spallanzani, and finally disproved by Louis Pasteur and John Tyndall in the 19th century .