…spontaneously generated beer

[The Leaven – exploring the relationship between science and religion (cont)]

One big difference between scientific and theological theory is that scientific hypotheses result from physical rather than spiritual observations, so therefore can be challenged by subsequent experimental investigation or  re-examination. For instance, many of Mendel’s laws and hypotheses, concerning genetic inheritance, have withstood this kind of scrutiny. In contrast, the theories of spontaneous generation presented by Antoine van Leeuwenhoek and several of his contemporaries, in the 16th century, were eventually disproved.

Leeuwenhoek was a draper, chamberlain and wine-gauger who specialised in making high quality magnifying lenses. He constructed an early form of microscope with a hand-ground lens that, although technologically advanced for that era, could only magnify specimens by about 250 times their natural size. Anyone who has observed pond water in a microscope during a science class will be aware that it contains a myriad of darting and spinning life forms of every description. These would have appeared astounding to the uninformed mind; it would naturally be assumed that these miniature life forms would eventually grow into something much larger. Leeuwenhoek used his apparatus to observe blood, serum, semen and other body fluids and found in it what he called ‘animalcules’. He perceived that animalcules had arisen spontaneously and were in fact microscopic extrapolations of larger entities. Most notably he imagined that spermatozoa were tadpole-like cells that contained their own circulatory and nervous systems.

Animalcules observed by Anton van Leeuwenhoek, c1795

In the latter part of the 16th century a number of scientists, including Leeuwenhoek and Nicolaas Hartsoeker, published drawings of sperm which they believed to be miniature versions of humans a theory known as  ‘preformation‘ .  In these drawings, miniature human foetuses were folded as they are observed in the uterus, but within the heads of sperm. Although, through lack of knowledge and the limitations of their equipment, these researchers were incorrect they attempted to give an intellectual framework to what they observed. Subsequent curiosity and the art of experimentation led to the abolishment of these theories but the discovery of microbes by Leeuwenhoek has cemented his name in scientific history.

Human forms in sperm drawn by Hartsoeker in 1695.

Incidentally, Leeuwenhoek, it seemed, was also interested in the properties of fermentation. Amongst the many microscopic structures he discovered were globular bodies, sometimes oval or spherical shaped, in droplets of fermenting beer. These were the first known microscopic observations of yeast cells.