This article was first published in the May/June 2023 issue of IQ, the magazine exclusively for British Mensa members.
Katie Cutforth explores a debunked scientific belief that fooled the brightest minds in the world at the time: the theory of spontaneous generation.
Where does new life originate? One of the earliest explanations – the theory of spontaneous generation – was posited by Aristotle in around 350 BC and was widely believed until the 17th century.
In his work On the Generation of Animals, Aristotle posited that animals and plants could appear spontaneously from non-living matter. Aristotle used this theory to explain the seemingly sudden appearance of organisms such as rats, flies and maggots on rotting meat or emerging from dust and mud. He also believed that slime creates oysters, sand produces scallops, and the hollows of rocks could give rise to limpets and barnacles.
The theory suggested that certain organisms are not descended from other organisms, but that creation requires certain environmental conditions. Aristotle believed non-living matter contained pneuma or “vital heat”, and from that vital heat, organisms could spontaneously appear.
Belief in spontaneous generation gave rise to other fascinating observations. In Georgics, the Roman poet Virgil described the process of “creating” bees in the carcass of dead oxen, a practice known as bugonia in the ancient Mediterranean region. In the 17th century, the Flemish scientist Jan Baptista van Helmont claimed that mice could arise from dirty cloth and wheat left in an open container for three weeks.
Of course, Aristotle’s theory was based purely on observing the world around him rather than on empirical scientific testing. But with the emergence of early modern science in the 16th and 17th centuries, the theory of spontaneous generation was called into question for the first time.
In 1668, Francesco Redi challenged the theory with experimental testing, by placing meat in partially covered containers and demonstrating that maggots would not appear on the meat. However, it wasn’t until the mid-19th century that the theory was widely discredited by the experiments of Louis Pasteur, and the idea that life could only emerge from other life was finally accepted.