One of the most fundamental axioms of biology is that all life comes from preexisting life. Still, until the later part of the 19th century, life was believed to arise from nonliving matter by a process called “spontaneous generation.” Ancient Egyptians, for example, thought mice arose from the mud of the Nile. In 1600, J. B. Helmont even reported “proof” for the spontaneous generation of mice, claiming that if wheat, cheese, and soiled linen are placed together in a jar, mice will eventually appear! This idea of the spontaneous generation of life from nonlife was so deeply ingrained in biological thought that it took nearly 200 years of experimental evidence to completely disprove it.
In 1650, Francesco Redi, an Italian physician, proved that maggots come from living flies and not from lifeless meat as was widely believed. This was a serious blow to spontaneous generation, but when bacteria were later discovered, it was thought that at least microorganisms might arise from nonlife. This notion too was finally laid to rest in 1864 by the great scientist (and creationist) Louis Pasteur, who demonstrated that bacteria can only come from living bacteria. When Pasteur reported his results before the French Academy, he confidently declared that “never will the doctrine of spontaneous generation arise from this mortal blow.” Pasteur never dreamed that the widely discredited evolutionary ideas of his contemporary, Charles Darwin, would one day become widely accepted by the scientific community, reviving once again the notion of spontaneous generation. In his book, The Origins of Life, evolutionist Cyril Ponnamperuma said,
It is, perhaps, ironic that we tell beginning students in biology about Pasteur’s experiments as the triumph of reason over mysticism yet we are coming back to spontaneous generation, albeit in a more refined and scientific sense, namely to chemical evolution.