Defining Darwin

Edward O. Wilson, Pellegrino University Professor Emeritus of biology at Harvard, is celebrated worldwide for his contributions to evolutionary biology, spurred by a lifelong passion for ants. He is also the distinguished recipient of two Pulitzer Prizes for nonfiction writing. But on Nov. 29, Wilson assumed the role of amateur historian to commemorate another famed scientist and writer. The Geological Lecture Hall was filled to capacity when Wilson delivered a lecture on “Darwin in the Twenty-First Century.” This lecture was hosted by the Harvard Museum of Natural History to celebrate the release of “From So Simple a Beginning,” a four-volume anthology of selected works by Charles Darwin published by WW Norton and edited by Wilson.

Wilson’s lecture was framed as a biographical timeline of Darwin’s life peppered with colorful anecdotes. He began by taking a jab at his own career, relating the story of a servant in the Darwin household who found her employer watching ants near the home of his neighbor, famed writer William Thackeray. “What a pity it is that Mr. Darwin doesn’t have a way to pass his time like Mr. Thackeray,” she remarked.

Wilson traced the development of Darwin’s theory of evolution from its humble beginnings in 1831, when a 22-year-old Darwin, recently graduated with a B.A. in divinity, embarked on an expedition that would uproot his plans for a clerical career. Accepting an unpaid position as naturalist on the five-year voyage of the HMS Beagle, Darwin traveled the world and lived what Wilson characterized as “one of the greatest adventure stories.” As he traveled from South America to Tahiti to Australia, Darwin was exposed to fossil evidence, natural calamities, and indigenous cultures that inspired him to seek a tangible explanation for the diversity of life.

In the years following the expedition, Darwin settled outwardly into the life of a gentleman. He pursued an assortment of natural history projects including the classification of barnacle species and the selective breeding of show pigeons, while furtively honing his theory of evolution. Darwin amassed a great deal of supporting evidence, but it wasn’t until 1859 that he was pressured into publishing his theory in “The Origin of Species” by the imminent emergence of a similar theory by Alfred Russell Wallace.

In “Origin,” Darwin stopped short of applying his theory to the origins of man, writing “light will be thrown on the origin of man and his history.” Not content for long with this platitude, he tackled the topic in subsequent publications. “The Descent of Man” (1871) expanded the theory of evolution to include humans and also documented physical differences between males and females in nature to support sexual selection, noting for instance that the size of the horn on male beetles enhances both their attractiveness and their chances of emerging victorious in combat.

In “The Expression of Emotions in Man and Animals” (1872), Darwin considered the evolution of instinct, and photographed professional actors to capture facial expressions associated with emotional displays. He died a decade later, but his work became fundamental to the establishment of psychology, ethology, and sociobiology.

“The Origin of Species” explains evolution as a two-part process. There are random variations among individuals; those with traits favorable to their given surroundings survive and procreate more successfully. Nearly 150 years after this powerful formulation, Darwin is revisited in a book by Marc Kirschner and John Gerhart titled “The Plausibility of Life: Resolving Darwin’s Dilemma.”

In a Nov. 30 lecture sponsored by Cambridge Forum, Marc Kirschner, professor and chair of Systems Biology at Harvard Medical School, presented a revisionist concept of “facilitated variation” at the First Parish Church. This modification stems from Kirschner’s belief that the current model of random mutations is inadequate. In the existing theory, random genetic mutations cause a plethora of variations, from which advantageous variations are selected for and perpetuated. But how is it possible for chance mutations to generate so many similar, well-functioning variations? Kirschner and Gerhart believe that random mutations are internally constrained.

To explain “facilitated variation,” Kirschner offers the following metaphor: It would take infinite time for a monkey with a stick to scrawl a random set of markings that would constitute the word “monkey.” If instead, the monkey was choosing randomly from the letters of the English alphabet, it could conceivably piece the word together in a decade. Given words in the English language, it could probably generate “monkey” in a day.

Kirschner believes that the creation of new body parts is similarly constrained, that genetic codes form versatile building blocks from which the same processes used to make a flipper can be modified to produce an arm, or a wing. It is difficult, he says, to conceive of the coincidental formation of a new limb, with completely new attachments and circulatory systems. But if instead you view the nervous system, the vascular system, and other crucial functions as exploratory processes that accompany migrating body parts, it becomes easier to conceive of variations that produce practical appendages. For instance, there are cases of polydactylism in which humans are born with extra fingers or toes, which contain the essential bone and blood vessel structures that make them recognizable. These extraneous digits are too common to originate from the combination of a random collection of mutations; rather, these novel structures illustrate the capacity of our bodies to adapt and compensate for changes in structure.

Both lecturers attempt to define the legacy of Charles Darwin in the 21st century. Kirschner views Darwin as an intellectual pioneer who laid the groundwork for new disciplines and healthy debate. Wilson portrays Darwin as a scientific giant, whose theory of evolution was a major victory in the perceived conflict between science and dogmatic faith, a rift that Wilson is not interested in bridging. “The input of religion on human history has been beneficent,” he said, “but there is something deep in religious belief that divides people.” The future of Darwin’s legacy is subject to the directional whims of succeeding generations, but it is certain that Darwin’s theory of evolution will continue to spark the curiosity of modern thinkers and inspire the search for truth.