SPRING QUARTER, 2006
Department of History
University of California, Irvine
Instructor: Dr. Barbara J. Becker
Lecture 16. Biogenesis
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Optical instrument makers improved microscopes enabling those following up on the pioneering work of Robert Hooke and Antoni van Leeuwenhoek to view specimens with greater clarity and confidence, even when highly magnified. By the nineteenth century, microscopists were treated to unparalleled views of microbial forms. Increased magnification revealed that some of the tiny moving specks -- barely visible under low power -- were, in fact, complex, self-animated organisms. But what about the new little specks now seen happily swimming around the field of view? They were so small their presence had escaped detection by previous observers. If they could be subjected to higher magnification, would they turn out to be complex living things, too? Just how small can something be and still be alive?
Advances in microscopy changed the terms of the debate over spontaneous generation. In the nineteenth century, the idea that some living beings -- like mice and flies -- could and did develop from lifeless matter could be laughed off as preposterous, but what about microbes? At some point, don't you get down to brass tacks: the inert chemical, electric, or mechanical whatever-it-is of which everything is made? Could it be that chance encounters, electrical attraction, and/or chemical cohesion was all that was needed to bring enough necessary ingredients together to produce a simple living "molecule"? [The word "molecule" was commonly used to describe microscopic particles, not, as today, to describe a fixed chemical aggregate of atoms.]
Girded with a range of ideas on what distinguishes a living from a non-living thing, and armed with their favorite microscopes and microbial infusions, life scientists entered the lists at the dawn of the nineteenth century and charged full tilt at one another until the field was littered with collapsed theories, abandoned methods, and bloodied reputations. You'll find the full story in Strick's Spark of Life.
Among the first contestants in the new debate on spontaneous generation were English physician, Erasmus Darwin (1731-1802) and English-born chemist Joseph Priestley (1733-1804).
In his epic poem The Temple of Nature, Darwin declared:
Hence without parent by spontaneous birth
Rise the first specks of animated earth;
From Nature's womb the plant or insect swims,
And buds or breathes, with microscopic limbs.
In Zoonomia, he likened life's organizing principle to that which chemists use to account for all the observed combinations of inanimate matter. In "Observations and Experiments..." Priestley decried Darwin's reintroduction of this "exploded" antiquated doctrine as unbefitting their modern age. Priestley criticized Darwin's erroneous interpretation of clear experimental evidence, his use of sometimes contradictory terms to confuse the argument, and -- above all -- his offensive godlessness.
New questions were brought into the debate in 1828 when English botanist, Robert Brown (1773-1858) announced his discovery of a constant, almost life-like motion in microscopic matter, particles he referred to as "active molecules." [Microbes were often called "living molecules". By using the word "active," Brown is leaving open the question of whether or not these particular microscopic particles are alive. To read more on "Brownian movement," see Strick's Spark of Life, especially the Introduction and Chs 1-2.]
In 1837, newspapers reported the astonishing news that living insects had been created artificially by country squire and self-taught English amateur naturalist, Andrew Crosse (1784-1855). Needless to say, the stories aroused considerable popular excitement and interest. However, his published account which described his experimental methods and interpretations raised both eyebrows and critical questions among members of the scientific community concerning the boundaries of acceptable research in the on-going debate:
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