Abiogenesis and Spontaneous Generation are two completely different things, even though they are the same thing.
The discovery of the microscopic world was to biology what Guttenberg’s printing press was to literature and widespread literacy.
But before the microscopic world was even conceived of, it had to be seen.
This brings in the curious personality of Zacharias Janssen. Although records of his time and life are sketchy – it isn’t even certain exactly when he was born, only that it occurred sometime between 1580 and 1588.
Janssen, who is widely regarded to be the inventor of both the microscope and telescope. Or at least he stole those ideas from those around him and copied them well in between his spectacle business and counterfeiting currency.
It’s also important to recognize that these arguments were coming to a head following 1637, when Rene Descartes published his Discourse on the Method outlining the framework for the scientific method. This book would revolutionize the way the people looked at the world and represented critical change from a reliance on philosophy alone to describe the world to one where ideas were supported by evidence from the natural world.
Descartes argued that “animals, and the human body, are ‘automata’, mechanical devices differing from artificial devices only in their degree of complexity. Vitalism developed as a contrast to this mechanistic view. Over the next three centuries, numerous figures opposed the extension of Cartesian mechanism to biology, arguing that matter could not explain movement, perception, development or life.”
Spontaneous generation, abiogenesis, and vitalism all point to the generation of life from inorganic (unliving) material. Most people equate spontaneous generation with the appearance of flies on a sandwich left out overnight- “Where did these things come from?!” -saying that the generation of life out of nowhere can, and does, occur every day. Abiogenesis is more commonly used to describe the single origin of life that set all living things in motion some 3.5 billion years ago (on this planet, at least). Both say life came from non-life at some point but differ on how frequently this occurs. Vitalism can be described almost as the magic within things that gives them the ability to create life.
The number of great minds that tackled this question is surprising. Today, it is easy to think that this these experiments are not worth doing. But, in fact, they were very worthwhile at the time. They answered the questions: ‘What is life?’, ‘Where does life come from?’, and ‘What distinguishes living from non-living things?’
The spontaneous generation of life was most often recognized as occurring on decaying matter, a fallen tree trunk becoming covered with moss and fungi, a dead animal spawning flies, etc. This idea was summed up in a theory of vitalism which states that, “living organisms are fundamentally different from non-living entities because they contain some non-physical element or are governed by different principles than are inanimate things”
Another explanation for the appearance of life was the theory of preformationism, which suggested that organisms arose from tiny, unseen versions of themselves. This idea was consistent with the notion that all life was created in one event, but that it was simply too small to be seen. The simplest illustration of this idea comes from Nicolaas Hartsoeker’s illustrations of human homunculi present inside of sperm that simply needed to grow up into larger (visible) forms. These ingenious ideas are reminiscent of the elaborate constructions imagined to maintain a geocentric universe and show how far the imagination is willing to stretch in order to maintain prior assumptions.
In 1665, Robert Hooke published his Micrographia thus establishing the publishing arm of the Royal Society. In it, Hooke presents beautiful images of natural and man-made objects as viewed through his microscope. These were among the first published images of such things and within its pages he coins the word ‘cell’ to describe the network of walls he observed in thinly sliced cork. He also presented other ideas and observations including observations of the planets and the wave theory of light.
In 1668, Francesco Redi put the idea to the test. He placed one piece of meat in an open jar and another in one closed off with cheesecloth. The open container represented what was commonly seen – flies appearing on the meat from nowhere. The covered jar represented an experimental condition in which pre-existing flies could not land on the meat and lay eggs on it. As he suspected, keeping flies away from the meat meant no new flies ‘appeared’ from nowhere on the meat.
“Life begets Life”
Redi’s experiment was adapted for examining whether micro-organisms arose spontaneously by John Needham in 1745 and Lazzaro Spallanzani in 1768. Both men boiled chicken broth (known already to kill any pre-existing organisms) and then kept the broth in sealed containers. Unfortunately, their results were mixed. Needham’s experiment was seen as open to contamination between boiling and sealing the containers, Lazzaro’s response used a vacuum to eliminate airborne agents, but many suggested that his work merely indicated the need for air for generation.
It wasn’t until Louis Pasteur took up the challenge in 1859 that the idea was challenged by an experiment that took these objections into consideration and demonstrated not only that spontaneous generation of life did not occur, but that what was previously seen as new life came – or preformed organisms, in fact came from airborne particles (organisms). Find a description of this experiment here and more on the direction of these ideas today here.