spontaneous generation

Aristotle

1500

He was the first to believe in spontaneous generation.

Redi's experiment - Francesco Redi

1626

Redi believed that maggots came from the eggs that were laid by flies so he put meat in various jars and sealed a few and left a few open. As he expected, only the jars that were open to air had maggots in it. This proved his theory because when the jars are sealed, flies were unable to lay eggs on the meat so there were no maggots.

Needham’s rebuttal - John Needham

1745

John Needham conducted an experiment to boil chicken broth to prove spontaneous generation. When he boiled chicken broth and put it in a sealed jar and microorganisms grew, people were more certain about the theory of spontaneous generation.

Criticism from Spallanzani - Lazzaro Spallanzani

1745

He modified Needham’s experiment and vacuumed the air out before sealing the chicken broth and boiling it. During that experiment, no microorganisms grew. However, some believers disagreed with Spallanzani and said he simply just proved that the theory needs air to work.

Pasteur puts spontaneous generation to rest - Louis Pasteur

1862

He performed a combined experiment of Needham’s and Spallazani’s. He boiled meat in a flask and heated the neck of the flask and bent it to an S shape. This allowed air to go into the flask but does not allow air borne microorganisms because they will settle on the S. Since no microorganisms grew, Pasteur proved the spontaneous generation theory wrong and also demonstrated microorganisms are everywhere.