Spontaneous generation

Aristotle thinks about spontaneous generation

300 BCE

Aristotle was the first to believe that spontaneous generation was how small life is created, that those organisms just appear there.

Redi's experiment

1700

Redi was a scientist that belived that spontaneous generation is not real. He made an experiment to prove that by putting meat into a jar and sealing it. With that he showed that when the jar was sealed the flies did not appear inside so rotting meat was not what made flies appear.

John Needham

1745

John Needham made an experiment to prove that microorganisms, such as bacteria, could appear by spontaneous generation. Making an experiment where microorganisms appeared in a broth after boiling it, to kill possible mircroorganisms that lived there before, and putting a cap on it so nothing could enter. Due to some experimental issues the result that Needham got was the one he was expecting and some microorganisms appeared.

Lazzaro Spallanzani

1770

Spallanzani made Needham's experiment again but instead of leaving the flask open while it cooled down he directlly closed it after being boiled and no microorganisms appeared. Not much people believed him and spontaneous generation was still thought to be how microorganisms appeared.

Louis Pasteur (1)

1859

Pasteur was the one that finally refuted this theory. He used a flask with a S-shaped neck. That permitted the air to flow by, so the 'life force' that the believers of spontaneous generation thought that was what created life was able to get in, but it trapped the microorganisms in the neck.

Louis Pasteur (2)

1859

There was not bacterial growth in the broth proving 'life force' didn't exist. But then he swiched the positon of the flask and those bacterias could get into the flask. With that he stated that life was created from other life.