Vitalism died a death of a thousand cuts. There was no single experiment, no one find that falsified the idea. Rather it was a shadow that shrank as the light of discovery grew.
One such event has become legendary in most modern science classrooms. In the late 18th century Italian physician Luigi Galvani was said to have brushed the sciatic nerve a frog he was dissecting with his metal instruments in such a way to cause the legs to twitch. This observation, it’s said, led to his research into connections between the emerging field of electrochemistry and physiology.
Galvani’s ‘electrical fluid’ theory paved the way for understanding how nervous impulses stimulate muscle movement, removing the need for some vague impetus or desire for movement.
Perhaps there’s some serendipity in the fact that a discovery made by Herman Boerhaave—who opposed Stahl’s metaphysical theories while building on his mechanistic contributions to physiology—eventually led to an event that shook the foundations of vitalism. In 1727 the Dutch physician purified urea from urine. A century later, in 1828, this humble human chemical became the first biological material to be produced synthetically. In his effort to make ammonium cyanate, the German chemist Friedrich Wohler earned the title of ‘father of organic chemistry’ by being the first person to create a chemical previously thought to be produced solely through organic processes.
“I must tell you that I can make urea without the use of kidneys, either man or dog. Ammonium cyanate is urea,” Wohler wrote enthusiastically to the chemist Baron Jöns Jacob Berzelius.
Decades later the French chemist and pioneer in microbiology, Louis Pasteur, settled the question on whether there was a force which could spontaneously cause basic, non-living materials to generate simple life forms. His experiment involved sterilising meat broth in a flask with a long, curving neck that permitted the contents to access fresh air, without permitting contaminants to inoculate the broth. While the typically vitalist theory of spontaneous generation was gaining fewer advocates, his simple experiment seemed to close the door on it for good.
Yet in the late 19th century one tiny bastion of vitalism held tight. If life was truly governed by the forces of physic and chemistry at even the most microscopic level, how could replicating units fracture and grow without reducing in complexity? How could all of the tissues and organs in an animal arise from something as simple as an egg, if that egg was fundamentally machine-like?
This was the question facing Wilhelm Roux (with whom we began Part 1). Although he had no answer, he set about investigating the embryonic development of a frog by using a heated needle to pop one of two cells in a newly divided zygote. On seeing the remaining cell grow into an incomplete ‘half embryo,’ Roux figured the eventual structure of an adult was already being established when the embryo was barely two cells in size. This inspired his mosaic theory, where the cells in a growing embryo come to act like tiles in a mosaic.
Several years later in 1891, a contemporary of Roux’s named Hans Driesch had his eye on the dividing cells of a newly fertilised sea urchin. He noticed teasing apart the cells allowed them to continue into normal larvae—far from the demi-sea-urchins Roux would have anticipated.
This wasn’t some amazing talent particular to sea urchins. Two decades later, American zoologist Jesse Francis McClendon showed pulling apart frogs’ cells would do the same thing. In hindsight, Roux would have done better to have separated than to have stabbed the replicating cells, which was more than likely responsible for stunting the development of the remaining embryo.
Hans Driesch showed that every cell in a growing embryo contained something that could produce a fully functioning adult. His conclusion? In his book The History and Theory of Vitalism, he cites a force which he describes as a passive form of teleology. He borrows Aristotle’s term for a tendency towards an outcome—”entelechy.”
Aristotle used the term energeia to describe a tendency for things to work or change, which is related to our modern term energy. Entelecheia relates to this concept, being a tendency to reach a particular end point. As such, vitalism was not dissimilar to energy, only it had a goal in mind—the differentiation of cells to produce a living thing.
Driesch’s theory was the last heroic stand of vitalism. It would take half a century for it to be once again superseded; this time thanks to a man better known for his dead-but-alive cats than his role in one of the greatest discoveries in the history of biology.
What is life?
Erwin Schrödinger was one of the 21st century’s greatest physicists. Yet in a series of lectures he delivered to the public in 1943, biology was his focus. Specifically, how can chemistry and physics account for the amazing processes that turn a single cell into something as complex as a human being?
His idea was insightful—an aperiodic crystal of the right size could not only contain enough information within its covalent bonds to create a wealth of complexity, it could be contained within the cramped space of a tiny cell.
DNA had been discovered nearly a century earlier. In the same year Schrödinger was giving his lectures, this molecule was shown to be responsible for transferring genetic information in bacteria. The two researchers who would later be credited with creating a model of the famous DNA helix structure—James Watson and Francis Crick—cited the book based on Schrödinger’s “What Is Life?” lectures as an inspiration behind their pursuit.
Schrödinger’s aperiodic crystal left vitalism nowhere scientific to hide. However, the second half of the century would see a significant resurgence in vitalist traditions such as homeopathy and chiropractic within various counter-cultures, not to mention the rise of creationism and Intelligent Design. Fringe beliefs in vitalism will perpetuate for much the same reason the theory existed in the first place: it serves as a counter to reductionist philosophies; it compliments other supernatural beliefs; and, it eases the discomfort of lacking a more convincing hypothesis. Yet as far as the scientific community was concerned, life’s mysteries simply were no longer mysterious enough to leave room for a ghostly force.