Refuting Spontaneous Generation: Redi, Spallanzani, Pasteur
The Fallacy of Spontaneous Generation
Spontaneous generation was a long-held belief, even described by Aristotle. Observation suggested that worms, flies, and other organisms emerged from mud, rotting meat, and moist places. The idea that life continuously arose from organic matter became commonplace in science. Today, the scientific community considers this theory refuted.
Francesco Redi’s Experiment
Francesco Redi, an Italian physician, conducted an experiment in 1668. He placed pieces of snake, fish, eels, and beef in four glasses. He prepared another four glasses with the same materials, leaving them open, while the first set remained sealed. Flies were attracted to the food in the open vessels, ate, and laid eggs. After some time, larvae appeared in these vessels. This did not occur in the closed vessels, even after several months. Redi concluded that the larvae (maggots) originated from flies, not from the spontaneous generation of decaying flesh.
Spallanzani’s Contribution
Spallanzani demonstrated that there is no spontaneous generation of life, paving the way for Pasteur. In 1769, after rejecting the theory of spontaneous generation, Spallanzani designed experiments to refute those of the English Catholic priest John Turberville Needham. Needham had warmed and then sealed meat broth in various containers. Finding microorganisms in the broth after opening the containers, Needham believed this demonstrated that life arises from nonliving matter. However, by prolonging the warming period and more carefully sealing containers, Spallanzani demonstrated that these wines did not generate microorganisms while the containers were sealed and sterilized.
Pasteur’s Definitive Proof
Pasteur: In the second half of the nineteenth century, Louis Pasteur performed experiments that definitively proved that microbes also originated from other organisms. Pasteur independently studied the same phenomenon as Redi. He used swan-necked flasks (similar to distillation flasks with long, curved necks). These flasks had very elongated necks that became increasingly thin, ending in a small opening, and shaped like an “S”. He placed equal amounts of beef broth (or nutrient broth) in each flask and boiled them to remove any microorganisms. The “S” shape allowed air to enter, but trapped microbes at the bottom of the tube.
The Origin of Life
The question of the origin of life on Earth has generated a specialized field of study in the natural sciences, aiming to clarify how and when it arose. The prevailing scientific view proposes that life came into existence from inanimate matter sometime between 4,400 million years ago, when conditions allowed water vapor to condense for the first time[2], and 2,700 million years ago, when the first signs of life appeared.[a] Ideas and assumptions about a possible extraterrestrial origin of life (panspermia), which may have occurred over the last 13,700 million years of the universe’s evolution after the Big Bang, are also discussed within this field.