Every practical observer of the world around him knew
that life develops spontaneously from nonliving matter by the action
of heat, light, moisture, and (after it was discovered) electricity.
Maggots come from decaying meat, and lice from sweat-soaked clothing.
Beetles develop from rotting wood, and horseflies from transmuted
It is difficult to put forward so thoroughly eroded
an idea as spontaneous generation today without arousing smiles
from the listeners. If ever a generally accepted idea was revealed
by careful experiments to be nothing but old wives' tales, spontaneous
Francisco Redi demonstrated more than 300 years ago
that meat, shielded from egg-laying flies by cloth, never developed
maggots. Others following him showed that nutrient broths that are
boiled and then kept isolated from airborne contamination never
Spontaneous generation died hard; its proponents
claimed that the life forces were delicate and were destroyed by
boiling. The early experiments were crude, and failed just often
enough to keep the controversy alive.
This reluctance to abandon spontaneous generation
was not an example of the obstinacy of the superstitious, but was
the stubbornness of those who considered themselves defenders of
the rational approach, and the only alternative to divine whimsy.