Spontaneous generation

Previous thoughts

1500

Aristotle was the fist person to believe in spontaneous generation. He thought life could indeed emerge from non-living matter.

Francesco Redi

1668

In 1668, Francesco Redi, an italian physician and poet, conducted an experiment against the spontaneous generation theory.

Redi's experiment

1668

Redi believed that maggots came from the eggs that were laid by flies, not from spontaneous generation. As we can see in the picture, he made an experiment where 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 were sealed, flies were unable to lay eggs on the meat so there were no maggots.

Lazzaro Spallanzani

1745

Lazzaro Spallanzani, an italian biologist didn't agree with Needham's conclusion so he modified his experiment as a rebuttal to Needham and to deny spontaneous generation.

John Needham

1745

However, John Needham, an english biologist, still believed in the spontaneous theory and he made an experiment on 1745 that helped to strengthen the theory.

Spallanzani's experiment

1745

First, he pured the broth into the flasks, sealed them and boiled them. He waited and didn't see any microorganism. Then, he opened the flasks and observed how microorganisms started growing rapidly. He concluded that the microorganisms emerged because of the contaminated air.

Needham's experiment

1745

He boiled chicken broth to kill the microorganisms in it and put the liquid into several flasks. Then, he sealed the jars and microorganisms grew, making people more certain about the theory of spontaneous generation.

Louis Pasteur

1859

In 1859, Louis Pasteur, a french scientists, finally proved the spontaneous generation theory wrong.

Pasteur's experiment

1859

He put broth in S curved neck bottles, boiled the liquid, waited and observed no microbiological growth. However, when he broke the neck of the bottle, exposing the broth to the air, observed how life started growing inside of the jars. This finally proved that life didn't occur spontaneously and as he said later in a lecture, "life only comes from life".