Imagine you are a great historical scientist and discover a disturbing truth about nature. Perhaps you discover that the world is not flat like a map, but is in fact round like a tomato. Or, maybe you discover that instead of the Earth having a special place at the center of the universe, it is a just an ordinary rock floating in space – distasteful and troubling revelations.

The naturalist, Charles Darwin, was in such a situation in 1859. Although a devout Christian, Darwin’s pursuits led him to discover the mechanism by which life on Earth developed from a common ancestor, leading to the obvious conclusion that humans evolved from their closest relatives, the great apes. It was the most disgusting idea of the century, and he was personally troubled by it for the rest of his life.

The path Darwin’s life took made him a likely candidate to discover the mechanism of evolution. He had an obsessive-compulsive personality, avidly collecting and cataloging beetles and other insects around his home. And, his own grandfather, Erasmus Darwin, had already put forth the idea of common ancestry in a poem 60 years earlier:

“The Temple of Nature”

Organic life beneath the shoreless waves
was born and nors’d in ocean’s pearly caves;
First forms minuk, unsceen by spheric glass,
move on the mud, or pierce the watery mass.
These, as successive generations bloom
New powers arquire and larger limbs assume
whence countless groups of vegatation spring.
And breathing realms of fin and feet and wing.

-Erasmus Darwin 1802

Most auspiciously, his family was affluent. His father, frustrated with Charles’ unending curiosity and lack of academic direction, eventually agreed to let him travel abroad with the HMS Beagle even though he considered it to be a complete waste of time. Darwin’s writings of the journey solidified his position as a well respected author and a well connected member of the scientific community.

He became close friends with Charles Lyell and Joseph Dalton Hooker, the most influential geologist and botanist of his time respectively. Through Lyell, he came to see the natural world as a gradually changing process. Hooker was a trusted confidante with whom he could share some of his troubling revelations. After writing his first essay on natural selection, Darwin told Hooker it was like “confessing a murder”. Hooker gave him the calm, critical feedback Darwin needed to proceed.

The final push came from the naturalist Alfred Russel Wallace who wrote his own version of natural selection in 1858, ahead of Darwin. Both Darwin and Wallace had been inspired by the ideas of the Reverend Thomas Malthus who promoted the idea that population outstrips food supply, and both came to similar conclusions about how this creates selection pressure in nature. Hooker and Lyell arranged to have some of their ideas presented at a conference in 1858. This inspired Darwin to kick into high gear and finish “The Origin of Species” the following year, unleashing the most consistent and comprehensive explanation of natural diversity ever conceived, then and since.

Darwin did not doubt the literal translation of the Christian Bible as a young man, but bravely came to question the nature of the Christian God after observing nature in exacting detail. His attitude was well summarized by his observations of the Ichneumonidae wasp. He wrote:

“I cannot persuade myself that a beneficent and omnipotent God would have designedly created the Ichneumonidae with the express intention of their feeding within the living bodies of Caterpillars, or that a cat should play with mice.”

-Charles Darwin 1860

Like Copernicus’ realization 350 years earlier that the Earth was not at the center of the universe, Darwin’s theory of natural selection pressed heavily against the religious views of his time. Though the religious conflict was never fully resolved in his own mind, Darwin lived to witness his theory gain acceptance in the scientific world and among much of the general public before his death in 1882.

Darwin might have found some solace in the poet Alexander Pope who foresaw the impingement of science upon religion. In “An Essay on Man”, Pope describes Man as passionate and ignorant, existing between God and beast, and that science is a valuable tool for understanding our nature, but not useful in answering religious questions:

Know then thyself, presume not God to scan,
The proper study of mankind is Man.
Placed on this isthmus of a middle state,
A being darkly wise and rudely great:
With too much knowledge for the Sceptic side,
With too much weakness for the Stoic’s pride,
He hangs between, in doubt to act or rest;
In doubt to deem himself a God or Beast;
In doubt his mind or body to prefer;
Born but to die, and reas’ning but to err;
Alike in ignorance, his reason such,
Whether he thinks too little or too much;
Chaos of thought and passion, all confused;
Still by himself abused or disabused;
Created half to rise, and half to fall:
Great lord of all things, yet a prey to all;
Sole judge of truth, in endless error hurl’d;
The glory, jest, and riddle of the world.

- Alexander Pope 1734

More:

• Full text of “The Origin of Species”
• Richard Feynman on doubt, uncertainty, and religion [video]
• Stephen Hawking rules out God [video]