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Lazzaro 

   Spallanzani 

 

Theodore Schwann

 

Louis Pasteur

 

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The idea of spontaneous generation goes back thousands of years. Aristotle believed in it.  It was not an uncommon sight to see worm-like maggots crawling in decaying meat and waste vegetables, and the only possible explanation seemed to be that the tiny worms arose spontaneously from the dead meat and garbage, just as, according to Athanasius Kircher, snakes apparently arose spontaneously from the soil.

Athanasius Kircher (1602 - 1680)

 
For centuries people believed in spontaneous generation and were able to interpret many things by assuming it to be true. Mice, frogs and turtles were said to come from water, air, decaying wood, or other non-living materials.  If swarms of insects, frogs or other creatures descended on a town or village, people would most likely think, ‘This is spontaneous generation acting again. These animals have grown out of the air or from water.’  Alternative explanations were rarely considered.

 
Jean-Baptiste van Helmont had an even better idea than Kircher for promoting spontaneous generation.  He maintained that if you put a dirty shirt with some wheat seeds, within twenty-one days mice would appear.  He even went as far as to predict they would be house mice.   

 

 

 

Jean-Baptiste van Helmont (1579 – 1644)

 
You can see how such idea could easily arise.  Imagine some corn scattered over a farmer’s coat left in a barn. It would almost certainly attract mice and if you did not see them get there, how could you explain their arrival?  Obviously there would have been alternative explanations, but van Helmont believed in spontaneous generation and any other idea would have been unacceptable to him because it did not fit in with his beliefs.  

 

Kircher and van Helmont did not ignore alternative conclusions intentionally and indeed they interpreted their observations as carefully as seemed possible to them.  But, as happens to many people, their beliefs strongly influenced their thoughts.    

 

 
Today we realise that however careful we are in our observations and interpretations, they often lead us to false conclusions. We can only observe as much as our senses and instruments allow us.  If you see tiny worms come from decaying meat and there is no apparent way in which they could have arisen it may be quite sensible to conclude that there has been spontaneous generation.

 

Bibliography

Grace Monger and Richard Gliddon eds, The Perpetuation of Life: revised Nuffield biology text 4, Longman 1975

Roy Porter, The Greatest Benefit to Mankind, Harper Collins 1997

G. Rattray Taylor, The Science of Life, Thames and Hudson 1963