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Why did scientists reject spontaneous generation?

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A herd of African elephants stands at the edge of the Chobe River in Botswana, drinking water with a backdrop of dry hills and scattered green trees. — life A herd of African elephants (*Loxodonta africana*) drinking from the Chobe River, Botswana.

Scientists rejected spontaneous generation—the archaic theory that living organisms develop from nonliving matter—through a series of rigorous experiments that demonstrated the principle of biogenesis, which holds that life arises only from preexisting life.12

The refutation occurred in stages:
* Higher Organisms: In 1668, Francesco Redi used controlled experiments with meat and gauze to prove that maggots were not spontaneously generated but were the result of eggs laid by flies.32
* Microorganisms: While Redi’s work addressed larger animals, the debate persisted regarding microbes. In the 18th century, figures like Lazzaro Spallanzani challenged proponents of spontaneous generation, but the issue remained contentious.42
* Conclusive Proof: In the 19th century, Louis Pasteur definitively settled the dispute. Using "swan-neck" flasks, he demonstrated that sterilized broth remained sterile unless exposed to airborne contaminants. His experiments proved that microbes do not arise spontaneously, providing the foundation for modern bacteriology and germ theory.42