Darwin: Caught Between Catastrophism And Gradualism

This past Saturday was Guru Purnima and I thought I would share a short post on two of Charles Darwin's mentors who had a big influence on him particularly in the early days of his scientific career. Adam Sedgwick and Charles Lyell were both geologists whom Darwin looked to for advice and inspiration. Although Darwin had a rather broad training in natural history, he initially considered himself a geologist. 

Just before embarking on his voyage aboard the H.M.S.Beagle in 1831, Darwin had spent some time doing fieldwork in Wales with Sedgwick. Over a couple of weeks Darwin became proficient in identifying rock types, describing outcrops, and mapping and interpreting the regional geology. He first met Charles Lyell after he returned from his voyage in 1836, although he had been regularly corresponding with Lyell about geology. 

Adrian Desmond and James Moore's biography Darwin: The Life of a Tormented Evolutionist has a lovely description of Darwin's early encounters with geology as he began his travels aboard the Beagle with the shadow of Sedgwick and Lyell following him around. 

The Beagle has reached St. Jago in the Cape Verde Islands, about 300 miles off the African coast. There Darwin saw a fossil bed, rich in shells and corals, about 30 feet above sea-level. 

An extract from Desmond and Moore's book: 

" Sedgwick in North Wales had inducted him into Cambridge-style geology- a science of violent crustal movements,wrenching strata, and mountain thrusts. But how had this seashell band arrived at this height above the ocean? Lyell's Principle's of Geology could help here, even though Henslow had said to beware. Lyell pictured a world constantly and slowly changing, with the past no more violent than the present - so that today's climates,volcanic activity, and earth movements balance one another, land rises in one area as it falls in another, not cataclysmically, as Sedgwick thought, but gradually".

 Darwin studied the fossil band and reasoned that the sea itself could not have fallen over the lifetime of St Jago islands (he was wrong in this assumption, but at that time the causal link between short term climate change and sea-level fluctuations was just not appreciated). The fossil layer did not exhibit any signs of a violent geological change. He decided a gradual uplift of the volcanic island was a better explanation for the stranded fossil bed.

Darwin became and remained a gradualist throughout his lifetime. Gradualism was one of the central ideas of his theory of evolution. That biological change too proceeds slowly was something he had imbibed from Lyell's thinking about geological processes. 

His geological observations about South America were well received by his two heroes. Lyell introduced him to Britain's science elite and Darwin quickly received invitations to join various Geological Societies. He was ready to embark on a serious geology career, but a nagging question about the nature of life eventually took him on a different path. 

His work on transmutation began consuming him as he wholeheartedly devoted his research energies to solve the 'mystery of all mysteries'; how do new species originate and change?  Even after he drifted away from any serious geological work, Darwin remained a close friend with both his mentors. But neither ever embraced his theories of evolution. Sedgwick and Lyell, rooted in Anglican tradition, could not shake of their religious convictions and accept a naturalist explanation for life that Darwin had proposed. 

 Sedgwick was particularly severe in his criticism. He wrote on reading The Origin of Species (quoted from Desmond and Moore's book):

.." Parts of it I admired greatly, parts I laughed at till my sides were almost sore, other parts I read with absolute sorrow because I think them utterly false and grievously mischievous. You have deserted... the true method of induction,and started in machinery as wild, I think, as Bishop Wilkins's locomotive that was to sail with us to the moon".

Sedgwick and Lyell's cold shouldering of his theory caused Darwin immense pain. He had always felt at home with the geology community of Britain whom he thought of as more of a gentlemanly fraternity than the cantankerous zoologists. Desmond and Moore describe how physically sick  Darwin felt after a futile conversation with Lyell about his ideas on transmutation. Shivers, shakes, fever, vomiting became routine maladies throughout his later life, manifestations of the inner turmoil of working on an extremely unpopular theory.  But the dogged and outstanding scientist that he was,  he could not and did not let his mentor's rejection persuade him to stop his work or change his thinking. Patiently and 'gradually'  he put the pieces together and built a body of work that changed the world forever. 

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