Tuesday, August 4, 2009

Spontaneous Generation of Mice

I made it back to the library today after having spent the last two weeks giving quality time to the family. I had been working on a chapter about preserved foods, many of which involved fermentation. My objective at the library was to get a footnote for an assertion about Louis Pasteur's contributions to the world of food. I had written something to the effect that although he had done some work regarding yeast and bacteria in the 1860s, his work wasn't accepted as valid until much later. That was an assumption I received from several other food writers, but none of them documented their work. I wanted to find something more concrete.

An initial search of the Deseret News (that pulse of Mormondom) yielded no results. A cursory look at other food history made very little reference to Pasteur, as we have relegated him to medical history. However, looking at his work directly, I found that his initial studies in the 1850s were directly related to yeast fermentation. Yes, we have been here before.

In 1857 there was an active debate about the notion of spontaneous generation. One camp believed that, along the lines of Alchemy, you could put the right elements together and generate something completely unrelated. The origins of these ideas seem to lie in the 1600s with a guy named van Helmont. He had a notion about stuffing an old shirt into a barrel that would create the spontaneous generation of mice in the course of three weeks. Others had similar ideas about the spontaneous generation of frogs from marsh mud, or eels from river water. These ideas persisted into the early 19th century.

In this atmosphere, the question of yeast carried similar arguments. One camp held that if you combine sugar and water, yeast will spontaneously generate. The idea that yeast was a living organism was only settled in 1837 when it was first seen under a microscope. This group also believed that yeast "did its thing" only upon decay. They thought that as yeast cells died, it caused the "decomposition" of the sugars in a like manner.

Pasteur and others such as John Tyndall however believed the opposite. In a series of papers presented to French Academy of Sciences in 1859, Pasteur argued that yeast particles floated in the air, and were attracted to sugary substances which fed them. The Academy sided with Pasteur and awarded him a prize for his work. In later years, John Tyndall asserted the dusty coating on the skins of grapes was yeast (which he had verified by microscope). He put to rest the idea that yeast spontaneously generated in grape juice by showing that wine makers had inadvertently introduced yeast by crushing the whole grape with its yeasty skin.

Even so, not all scientists were convinced. In the face of this evidence, Pasteur's primary detractor Justus von Liebig continued to hold to the decomposition and spontaneous generation theories into the 1870s. Indeed, Tyndall was compelled to continue arguing against spontaneous generation into the 1880s, when Pasteur had moved on to medical applications. The broad popular acceptance of Pasteur's work in the 1850s didn't come until after his rabies vaccine proved its success. Many continued to disbelieve Tyndall's arguments about "Floating-Matter of the Air" and "animalcules" (microbial life forms) nearly to the end of the century.

Today it seems ludicrous to us, this idea that life could just sponaneously generate. Even if we don't thoroughly understand the conversion of lactic enzymes to lactic acid, we understand there is a cause and effect relationship driven by basic scientific principles. A hundred and fifty years after Pasteur, it is part of our popular view of the world. The curious thing to me is that 150 years after Darwin, many people still argue against evolution. I suppose the evolution argument requires a bigger petri dish than we have at the moment.


Randy Lynn said...
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Tawna said...

Very interesting. I hope you got your flash drive back. I didn't know there was yeast on grapes. That seems obvious now that there is some in there somewhere with the wine and everything, but how interesting for him to find it under a microscope. Did you ever read "Galileo's Daughter"? I was amazed at how primitive the instruments were at the time, and that he could STILL make all those discoveries. Some people are just brilliant. If I can be above average, I'll be thrilled.