Monday, January 7, 2013
Charles Darwin’s theory of evolution by natural selection was a synthesis of ideas that had been brewing for centuries, indeed millennia, about the origins of and relationships between the organisms inhabiting the planet.
That its time had come is evidenced by the nearly identical theory of Alfred Wallace that almost scooped Darwin’s publication. In what follows, I will briefly outline Rebecca Stott’s book “Darwin’s Ghosts,” which provides an excellent sketch of the people and ideas before Darwin.
In the third and subsequent editions of “The Origin of Species,” Darwin added a preface called “An Historical Sketch”. This is a list, along with some brief notes, of some 30 men who had made significant contributions to understanding the relatedness of all organisms, living and extinct.
The list begins in the fourth century BC with perhaps the first natural philosopher, Aristotle. Three books, “Parts of Animals,” “The History of Animals” and “On the Generation of Animals” represent the first systematic, empirical attempt to understand the nature of life.
In a prelude to what would follow over two millennia later, Aristotle wrestled with the most appropriate classifications of the animal kingdom. He cautioned his students to investigate what is, not what might be.
He was the first to enunciate this most fundamental principle of science, that nature is what it is and is not obliged to conform to our wishes.
In the middle of the ninth century a man named al-Jahiz, who lived in Basra in what is now Iraq, wrote a book entitled, “Book of Living Beings.” This was a rudimentary harbinger of the theory of evolution by natural selection that would follow a millennium later.
The list remains sparse until the late 15th-early 16th century when the likes of Leonardo da Vinci and Bernard Palissy speculated about fossil seashells found on mountain tops.
By the early 1740s the pace quickened, hastened on by introduction of magnifying glasses and improvements in microscopes. Abraham Trembley demonstrated how fresh water polyps (Hydra) were actually animals and, when cut into parts, each part regenerated a new polyp. At the same time Charles Bonnet discovered aphids could unexpectedly reproduce asexually.
These were early days in the development of scientific methods. Bonnet cautioned Trembley to follow Francis Bacon’s admonition to avoid hypothesizing and just collect and sort facts. But the very act of sorting data, looking at shared characteristics energized their minds.
These discoveries, and others that soon followed, caused uproar by challenging long held ideas about the laws of nature. Furthermore, they were transforming science from a discipline of pure observation and classification to one including drawing inferences.
In 1748 a book was published entitled “Telliamed,” or “Conversations Between an Indian Philosopher and a French Missionary.” While serving as French consul in Egypt, the author, Benoit de Maillet, studied the region’s unique geology, history and unfamiliar ideas.
As had been the style used by Galileo to deflect accusations of heresy, the book entailed an imaginary conversation. In the course of the conversation the Earth was proposed to be billions of years old and that its surface had been gradually transformed over that time while all existing animals had arisen from primitive aquatic organisms.
Back in France, these were heady and dangerous times for such disquieting ideas. The Comte de Buffon and Denis Diderot were routinely hounded by the authorities for their scandalous writings.
Diderot was publisher of Encyclopedia (yes, he originated the encyclopedia concept) which was designed to bring knowledge to the common man on such subjects as fossils, glaciers, the sea, mountains, geologic strata, earthquakes and much more. The section entitled “Animals” had excerpts from Buffon’s “Natural History.”
One of the milder criticisms of “Natural History” said it would “… do harm to Natural History by bringing back the taste for hypothesis”. Again, we see the struggle to define natural science. Shame on Buffon for suggesting he saw “imperceptible shadings” between species and for thinking all species might have a common origin.
One cannot overlook Charles Darwin’s grandfather, Erasmus. His “Zoonomia,” or the “Laws of Organic Life,” published in 1794, was a medical book on the functioning of the body. In it he wrote about the “great similarity of the warm-blooded animals” going on to ask, “… would it be too bold to imagine, that in the great length of time, since the earth began to exist, perhaps millions of years … that all warm-blooded animals have arisen from one living filament”.
Jean-Baptiste Lamarck and Georges Cuvier epitomized the ongoing battle to define science. Cuvier was one of the founders of the fields of comparative anatomy and paleontology through studies of living animals and fossils. His most famous work, The Animal Kingdom was published in 1817.
As with Cuvier, Lamarck was a taxonomist, concerned with classifying organisms. He started as a botanist (plant scientist), but, in 1801 published “Natural History of Animals Without Backbones,” followed by “Researches on the Organization of Living Bodies” in 1802.
His was truly the first draft of a comprehensive theory of evolution. He argued life became increasingly complex as it adapted to environmental forces. Cuvier opposed such thoughts, arguing the natural sciences should stick to data collection and classification without venturing hypotheses on their implications.
Robert Grant, author of “Outlines of Comparative Anatomy,” toiled over how sea sponges might yield clues to the increase in complexity of life. He argued successive geological strata showed a progressive, natural succession of fossil animals.
Geoffroy Saint-Hilaire espoused an underlying unity of design among organisms, and that there might have been transmutation of species over time. In addition to his work in comparative anatomy and paleontology, he did extensive work comparing embryo development in different animals.
Space precludes naming all the contributors, but Carl Linnaeus, father of modern taxonomy, deserves mention for the system of classification he developed in the mid-1700s.
Darwin was a perfectionist, dragging out the writing of Origins so it nearly cost him the credit he deserved. Hot on his heels was Alfred Wallace, a solo naturalist working tirelessly in the forest of the Malay Archipelago. Poor Wallace had formulated substantively the same theory as Darwin, but he was far away and lacked the reputation and connections of Darwin.
Though the naturalists before Darwin had useful insights, in many cases they had parts that were wrong and all were incomplete. Primarily they were wrong because their knowledge was insufficient. Sometimes they were wrong because they were trying to make new information fit outmoded ideas.
Darwin and Wallace’s great genius was in connecting the dots between ideas that had been brewing for a long time and for describing the mechanism, natural selection, which tied it all together.
In my next article I will tell how new knowledge in such fields as genetics, microbiology, organic chemistry, and developmental biology has augmented Darwin’s ideas. “On the Origin of Species” was ground breaking in formulating an idea whose time had come and upon which biology could be founded.
Steve Luckstead is a medical physicist in the radiation oncology department at St. Mary Medical Center. He can be reached at firstname.lastname@example.org.