What Has Science Done?

Monday, June 20, 2005

The Origin of the Origin of Species

How did Charles Darwin come to formulate his theory of biological evolution by natural selection? The Origin was published in 1859, and the laws of Mendelian genetics would only rediscovered at the turn of the last century, and it would be another fifty years till Watson and Crick discussed in detail the structure of the molecule of inheritance. The story is important not only of importance for historians of science but also as a pedagogical tool in biology classes.

Fossils were being uncovered at an ever increasing rate throughout the 19th century, with even U.S. president Thomas Jefferson using the East Room to store his bone collection from Big Bone Lick. These dead animals often slightly resembled living species found on other continents like the elephants and sloths, but some which became known as dinosaurs to their discoverers were like nothing they had ever seen before. The problem was of how to fit these dead animals only known to exist because of their bones into the contemporary view of natural history. A discussion of natural history, unlike natural philosophy (physics, astronomy, chemistry) had not shed its connection to theology at this time. One widely held theory of geology was that of catastrophism which stated that changes to the Earth were due to global occurrences like a flood which do not occur with an observed regularity. Though not an explicit recitation of the story of Noah, this theory would mesh well with a Christian view of God changing the Earth with water or fire from heaven. Then to explain the fossils found in various layers of sediment, natural historians proposed that these catastrophes occurred numerous times throughout history wiping out all life on the planet, and God would then create new life again in a manner like that described in Genesis 1.

So sticking with the current theme of geology, we move onto Sir Charles Lyell whose work developing the theory of uniformitarianism crucial to the Origin's development. Uniformitarianism is a theory which states that changes in the surface of the Earth can be attributed to slow-acting observable processes like that of erosion. In order for erosion to create something as large as say, the Grand Canyon, it would require an enormous amount of time. Efforts to calculate the age of the Earth in the 19th century involved studies of salting of oceans, the condensation of gas nebula into stars, and the cooling of molten metal. A commonly stated figure was 100 million years, which Huxley decried as too small, though greater precision in age calculation was only brought on by the discovery of radioactivity and atomic isotopes. But back to our supposed main character Charles Darwin. He was a very close friend of the elder Lyell and an active proponent of uniformitarianism himself. He took a copy of Lyell's masterwork, The Principles of Geology with him on the HMS Beagle and his surviving 1837 copy is heavily annotated.

For the biology portion of this history, we have start with the Swedish ecologists Carl Linnaeus who developed the system of organizing species by their external and internal characteristics (taxonomy). Taxonomy can be a contentious enterprise, as anyone whose opened a few biology texts will note, since views of what phylum or family a particular species belongs in varies among scientists even today. Jean Baptiste Lamarck, a French biologist, created a taxonomy based on a line of increasing complexity with humans, as one could expect, being at the pinnacle. Lamarck's theory of evolution was that animals gained new forms by the inheritance of acquired traits, and that each successive generation would further develop along the line. He did not believe in extinction, but that evolution produces ongoing spontaneous generation of new species. Darwin calls Lamarck's hypotheses absurd quite regularly in his notebooks with regard to both extinction and taxonomy. From Darwin we get the familiar branching tree model, but more will be said on this in a minute.

In 1830, at the age of 21 Darwin goes off on the HMS Beagle, a survey vessel to study the geology, fauna, and flora of South America. He writes about the importance of Lyell's geology while studying layers of sediment in Patagonia and how earthquakes can raise land. The book about his trip, The Voyages of the Beagle became a best seller in England documents the discovery of extinct species of gaunaco and armadillo buried in the ground in the same area as contemporary species. The questioned asked was, are these animals at all related? From uniformitarianism, Darwin knew that the Patagonia, the Andes, and the Galapagos were not always as they were when he saw them. So if these species were related, it is another jump to speculate how if possible could the changes in the habitat create new species. The final piece in the puzzle of Darwin's though comes from an unlikely source, political economist Thomas Malthus, whose "Essay on Population" produced a eureka moment for Darwin as well as Alfred Russel Wallace. Darwin artfully describes the importance of population pressure and the struggle for limited resources in the 1845 republication of the Voyages, particularly in his description of the variety of different finches found in the Galapagos Islands. The finches he described were all the descendent of a single ancestor from South America, not the product of special creation, and the variety they displayed were due to available food supply on each island, which would make certain beaks more preferable then others. Those who ate more, were healthier, more apt to survive to produce offspring who were themselves healthy.

Charles Darwin had his theory of evolution by natural selection in his head by 1838, but only published The Origin of Species, at the request of Lyell in 1859, almost thirty years after he had left to tour South America. In this age of publish as fast as you can, one right asks why thirty years of mulling the problem. Darwin, plain and simple was obsessive about his theory, wanting to make it as solid as he could with mounds of evidence like that of his studies in orchids and barnacles. Understanding how controversial it would be in his own time, he wanted to make it irrefutable, and the comments in the Origin follow from his inability to fit every anomaly into his theory upon its 1859 publication. He was working on his Big Species Book, when the writings of Wallace compelled him to publish his theory, so without external motivators he may have waited even longer to publish.

My apologies for making this entry drone on forever, but few things in history are ever able to be squeezed sensibly into 100 words, and many historians just have a gift to gab. I also hope in a latter entry to go over all those contemporaneous arguments used against Darwin that are often thrown about as an aside by creationists to contend that evolution has always been controversial. Not only do we need better teaching of science in this country, but better history curricula as well. Bleh!