The defenders were wrong. Louis Pasteur sealed the fate of spontaneous generation in a series of careful experiments, in 1861. He demonstrated clearly that microorganisms are carried in the air, and that they grow in previously sterilized broths only when the broths are contaminated by air or similar sources.

"All Life from Life" became one of the fixed and immutable points of biological dogma. This led to a dilemma that has been expressed as the chicken-and-egg paradox.

Which came first, the chicken or the egg? If all eggs come only from chickens. and if all chickens come only from eggs, then there must once have been either a first chicken or a first egg. This demanded a Creator, a celestial clockmaker who at least set the entire machinery of life in motion before stepping back to let things take their "natural" course thereafter.

The operations of life and the mechanisms of life hence were areas of fruitful research, but the origin of life was not a legitimate subject for scientific investigation. Pasteur apparently had disproved the only theory of the origin of life that was subject to scientific testing.

While Pasteur was tamping the last dirt over the grave of spontaneous generation, another extraordinarily important idea was developing in biology - one that would not have its impact on chemistry for nearly a century. This was the theory of evolution, as proposed by Charles Darwin, Alfred Wallace, and the very able propagandist, Thomas Huxley.