Charles Darwin adored his first cousin - love Vs scientific fear of inherited disease?

As I discussed, Charles Darwin (1809-82) was sick all his life, but he had no idea why. It wasn’t until 2013 that John Hayman solved the problem in Charles Darwin’s Mitochondria. Charles’ ill­ness, his brother's, mother's and others on the mother’s side showed a gen­etic pattern of maternal in­her­it­ance that was the hallmark of mitochon­d­rial mutations. The symptoms were severe depression, an­xiety, nau­sea, vomit­ing, visual hallucinations, headaches and cardiac pal­pitations.

Emma and Charles Darwin loved each other and had 10 children together, 

even though they were first cousins. 7 of their children grew into healthy adults.

Charles inherited any weaknesses his own parents had PLUS he also chose to marry, of all the possible women, his own first cou­sin Emma Wedg­wood. It was therefore important for Prof Hayman to dis­cov­er what happened to the next generation. Hayman showed that Charles Darwin’s children were unaffected.. since defective mit­o­chondria can only be in­her­ited from the mother. And Emma Wedgwood was genetically clean!

Now back to 1832. Charles Darwin set out on a 5-year, around-the-world voyage on the naval ship HMS Beagle. As the ship exp­lored the oceans and coasts of the Southern Hemisphere, it dropped Darwin off at various ports, for his expeditions. There Darwin collected thousands of specimens of extinct and still-living plant and animal species.

In 1838, 2 years after disembarking from the Beagle, Darwin fell deeply in love. Emma was an intelligent young woman, an excel­lent pianist who had studied briefly with Chopin and the grand-daughter of Josiah Wedgwood, the famous potter who’d made his fortune making gorgeous porcelain.

Yet at the same time that Darwin was falling for Emma, he didn’t feel at all ready for marriage. In his note book Darwin wrote of his fears about giving up bachelorhood. “If I married tomor­r­ow: there would be an infinity of trouble & expense in getting & furnishing a house, morning calls, awkward­ness, loss of time every day”. Thinking about Emma and imag­in­ing marriage as slavery, Darwin scribbled two lists: ‘Not Marry’ included freedom to go where one liked and loss of evenings. ‘Marry’ included charms of music & female chit-chat. If only Prof John Hayman could advise Darwin back then!

Emma was shocked when Darwin proposed. She’d had no idea that they had been courting, thinking instead that they were friendly relat­ions who enjoyed occasional fireside chats. But she was 30 and still single, so she accepted his proposal quickly.

In Jan 1839, they married. Though the love between Darwin and Emma proved unshakable, Darwin knew that Emma’s grandfather Josiah Wedgwood was his grandfather too!

On the Origin of the Species by Means of Natural Selection (1859).

Darwin understood the consequences of inter-breeding.

Charles and Emma Darwin eventually had ten children. Mary died 3 weeks after her birth. 10-year-old Annie died of a res­pir­at­ory dis­ease, probably tuberculosis. 18-month-old Charles died of scarlet fever. The other children lived to normal adult­hood.

Of course many C19th children died in the weeks after birth, even in families that were not impoverished. Antibiotics were unknown. Raising only seven out of ten children to mat­urity might have been about average for middle class British families then. Darwin fretted anyway that his dec­ision to marry his first cousin was the cause of his child­ren’s weaknesses. And of all men on the planet, Darwin should have known bet­ter. In the years before his marriage, he’d long been investig­ating the consequences of inter-breeding!

Analysing his specimens and writing books about them was Darwin’s life role. He had long developed the ideas that would comprise his break­through work, the 1859 On the Origin of Species by Means of Natural Sel­ection. In it Darwin prop­osed that all of the complex plants and animals of the modern world were the progeny of only a few simple organisms that existed eons ago. The deviation of modern organisms’ morphology from that of their pre-historic prog­enitors was a result of Natural Select­ion, the ability of organisms with certain genotypes to survive and thrive in the environment, more than their siblings. As the surviving organisms created progeny, their characteristics helped define the species.

Buttressed by the huge specimen library that Darwin collected before his travels, Origin of Species re-aligned Western thought about life on earth. Meanwhile other scientists and religious lead­ers responded with ideas of their own. Origin was such compelling reading that it quieted the some­times acrimonious conversation.

12 years after Origin was published and 32 years after the Darwins married, Charles released Descent of Man, and Selection in Relation to Sex (1871). It applied Darwin’s theory of evolut­ion to the human species, and boldly proposed that humans and mod­ern apes shared a common ancestor. It also outlined how the mating preferences of an­imals within a species could influence natural sel­ection. A year later, Darwin’s The Expression of the Emotions in Man and Anim­als (1872) catalogued a wide range of gestures and behaviours shared by animals and hum­ans. The presence of nearly identical ges­t­ures across species sug­gested that the species’ emotional experiences were similar.

Charles Darwin's state funeral, Westminster Abbey, April 1882. 

Wood engraving. wellcome collection

The Darwins’ marriage lasted 43 happy years, despite him having been so ill. Regardless of how many scientific symposia Darwin was invited to attend, he rare­ly agreed to spend a night away from Emma - she tended to his every need, enabling Darwin to work at home peacefully. The memor­ies of anx­iety, grief and joy were indelibly inscribed on his brain when he worked inside his study. Did his love for Emma colour his later scientific writings?

Darwin was buried with a grand state funeral in West­min­ster Abbey. Being enshrined with the great stars of British science was a well-deserved honour; to this day his work profoundly influences all of the biological sciences. Thank you to Rebecca Coffey's journal paper.