-
530 BCE
Early View on the Spontaneous Generation: Pre-Aristotelian Philosophers
Anaximander was the first western thinker to believe that everything arose out of the elemental nature of the universe. He claimed that living creatures were first formed in the "wet" when acted on by the sun. -
330 BCE
Foundation of the Spontaneous Generation: Aristotle
Aristotle set the foundations of the spontaneous generation. He wrote a book called "The History of Animals," in which he states that living things come from nonliving things because nonliving materials contain "vital heat" that generate life. -
First Attack on the Spontaneous Generation: Francesco Redi
In 1668, Francesco Redi, an Italian scientist, conducted an experiment to disprove the spontaneous generation by placing meat in a variety of flasks. Some jars were left open while some were sealed and others were covered with a gauze. Days later, he found that only the open jar contained maggots. Through this experiment, Redi demonstrated his theory that the maggots came from fly eggs. -
John Needham's Attempt
In 1745, John Needham, an English biologist and clergyman designed an experiment in which he considered to be definitive. He placed gravy into a bottle and briefly boiled it to kill any germs inside, then sealed it. Later on, he noticed presence of microorganisms in the gravy and announced that he proved that life had been created from non life. However in reality, he simply did not heat the gravy long enough to kill all the microbes. -
Lazzaro Spallanzani's Turn
In 1768, Lazaro Spallanzani, an Italian scientist, repeated Needham’s experiment with some modifications. Spallanzani boiled broth in flasks, then left one group of flasks open, and the other sealed. No microorganisms formed inside the sealed flasks, while the open flasks became cloudy due to contamination with microorganisms. He concluded that microorganisms don’t form from air, it forms from other microorganisms. Many disagreed with him and believed that air was needed for life to generate. -
The End to the Debate: Louis Pasteur
In 1859, Louis Pasteur repeated Spallanzani’s experiment but left the flasks open to the air. He designed special flasks with S-curved necks that prevented outer materials from entering the broth. He boiled the broth, which kept clear for a year, but once he broke off the curved neck, the broth became contaminated within days. Pasteur concluded that the contamination was due to microorganisms in the air that wasn’t able to enter through the curved neck. Pasteur finally ended the debate.
