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Period: 611 BCE to 547 BCE
Anaximander (Pre-Socratic Philosopher)
Anaximander believed that everything came from the universe’s nature which he called the “apeiron” or “unbounded”, and that living creatures were formed in the “wet” when acted on by the Sun, and they were different then than how they are currently. He also thought humans were a kind of fish and took a long time to develop. -
Period: 588 BCE to 524 BCE
Anaximenes (Pre-Socratic Philosopher)
Anaximenes believed the air was the element that gave live, motion and thought. He claimed that there was a primeval terrestrial slime that was a mix of earth and water, from which the suns’ heat formed plants, animals, and humans directly. -
Period: 576 BCE to 480 BCE
Xenophanes (Pre-Socratic Philosopher)
Xenophanes traced origin of mankind back to the transitional period between the fluid stage of the earth and the formation of land. He also believed that plants and animals formed under the influence of the sun. -
Period: 500 BCE to 428 BCE
Anaxagoras (Pre-Socratic Philosopher)
Also believed in the terrestrial slime theory, but also thought that the seeds of plants existed in the air from the start. -
Period: 495 BCE to 435 BCE
Empedocles (Pre-Socratic Philosopher)
Empedocles accepted the theory of the spontaneous generation of life, yet believed there had to be trials of combinations of parts of animals that were formed. Successful combos formed the species we now see, while the unsuccessful ones failed to reproduce. -
Period: 460 BCE to 370 BCE
Democritus (Pre-Socratic Philosopher)
Democritus also believed in the terrestrial slime theory. -
Period: 384 BCE to 322 BCE
Aristotle (Greek Philosopher)
Aristotle said that there were four elements (earth, air, fire, and water) and a fifth essence later named the “quintessence” or “ether” that existed only beyond the moon, in the heavens. The principles of the elements: hot, cold, dry, and wet. The properties of organisms were due to a mix of these principles and elements in each part of a body, added to an animating force called “pneuma”, which means “soul”. There were numerous souls; growth, motion, sensation, thinking, and in humans, reason. -
Period: Jan 12, 1580 to
Johannes Baptist van Helmont (Physician and Alchemist)
He believed that mice arose when a flask of wheat and old rags was put in a warm dark closet. -
Period: to
Francesco Redi (Italian Physicist and Naturalist)
He demonstrated in 1668 that maggots did not arise spontaneously, but from eggs laid by adult flies. -
Period: to
Gottfried Wilhelm Leibniz (German Philosopher, Mathematician, and Scientist)
He claimed there were fundamental “living molecules” called “monads” from which all things sprang. Very simple organisms were comprised directly of monads. -
Period: to
Georges-Louis Leclerc (French Naturalist) and John Needham (Roman Catholic Priest)
Attempted to disprove the work of Louis Joblot, who had tried to show that simple organisms were not spontaneously generated by boiling a medium, placing one part in a sealed vessel, and the other in an open one. The sealed one did not become infused with organisms. To prove the medium could still support life, he exposed the sealed material in the air and it was soon filled with organisms. Leclerc and Needham's results: Boiled or not, sealed or not, life arises in the vessels. -
Period: to
Lazzaro Spallanzani (Italian Biologist)
Spallanzani wanted to disprove Needham and Buffon’s results.
His Result: No life would develop as long as the flask was kept sealed. -
Period: to
Jean Baptiste Lamarck (French Naturalist)
Assumed that each species was the result of an independent event of spontaneous generation. -
Period: to
Lorenz Oken (German Biologist)
Oken followed the “slime” theory of the origins of life like Anaximander. He also believed spontaneous generation occurred where land and sea met, and tiny bladders of foam embodied three life principles: feeding, respiration, and digestion. -
Period: to
Theodor Schwann (One of the founders of the cell theory, German Physiologist)
Schwann's experiments showed that airborne microorganisms instead of spontaneous generation may be responsible for fermentation. -
Period: to
Louis Pasteur (French Chemist and Microbiologist)
In 1859, Pasteur proved that nothing grew in broths unless the boiled flasks were broken open, showing that the living organisms that grew in such broths came from outside, like spores on dust, rather than being formed within the broth. He famously used swan necked flasks for his experiments, and he is now known for thus refuting the theory of spontaneous generation for the formation of all organisms.