The Sad Side Of Darwin’s Discoveries About Inbreeding

“Is that drooling problem you have due to genetic inbreeding, or are you just really attracted to me?” —Darby Conley, “Bucky Katt’s Big Book of Fun”

In A Nutshell

Charles Darwin wrote an entire treatise on the impact of inbreeding in plants and animals. He noted their infertility problems, their tendency to be ill and weak, and their susceptibility to disease. His findings made him look at his own family and his own sickly children. Married to his first cousin, he had 10 children. Three died before the age of 10, and three left behind no children of their own. More research into his family tree has found a whole trend of cousins marrying cousins, and it’s likely Darwin’s family was suffering from the very thing that he was researching.

The Whole Bushel

Charles Darwin has made some incredible contributions to science and biology and was one of the first researchers to explore and document the negative consequences that we all associate with inbreeding. He crossed both plants and animals to produce inbred offspring and documented the results, and a recent study had found that the same exact thing was happening in his own family.

Darwin ended up having 10 children with his wife, Emma Wedgwood. Wedgwood was also his first cousin, and he often wrote about his concerns for his children. Three died young after contracting various infectious diseases. He often reported that the others seemed unusually weak and sickly.

Darwin himself had been a sickly child, and the journals and diaries he wrote paint a picture of someone who was obsessed with the state of his own health. He recorded all of his various ailments, from heart palpitations and dizziness to numbness in his fingers. He participated in all the medical treatments that were the rage in his day, submitting to water therapy and electric currents applied to his body. He took opium and mercuric chloride and refused to eat sugar, butter, or anything with spices.

One of the most visible effects of Darwin’s ill health was his beard. Part of his problems involved a skin disease that made shaving unbearably painful, which is how he ended up with the beard we know today. After Darwin died, he was diagnosed with Chagas disease, most likely contracted when he was bitten by a bug in South America. It’s also been theorized that he suffered from Crohn’s disease or possibly a psychosomatic stress disorder that came from the knowledge of how much his theories would change the world.

A recent study of his family tree suggests that all the medications and miracle cures in the world couldn’t really help him: The cause of his problems was likely in his genes.

There aren’t as many branches as you’d think there should be in Darwin’s tree. He married his first cousin, who was the daughter of a pair of third cousins. Three of her brothers also married their first cousins, and going back even farther, researchers found more uncles that married their own cousins.

Darwin’s own children had no real outward signs of deformities and showed no physical consequences of inbreeding, but they were definitely there. Susceptibility to bacterial infections is associated with inbreeding, and that was the cause of death of two of his children. One child, who was noted not to have a normal early development, died at 18 months. Three of the children who lived to adulthood and married had no children. (Infertility is also associated with inbreeding.)

When researchers looked at the larger family picture, they found some uncomfortable numbers. Through four generations of the Wedgwood-Darwin family, there were 176 children. A large number (21) of them died before they reached 10 years of age. When a computer program was tasked with mapping out Darwin’s genes, it was found that his children had a 6.3 percent chance of receiving duplicate copies of genes from their parents. When that’s applied to the possibility of developing genetic disorders, it means there’s about a 2 percent chance of a child being born with it.

Show Me The Proof

Featured photo via Wikipedia
NY Times: In Darwin Family, Evidence of Inbreeding’s Ill Effects
BioScience: Was the Darwin/Wedgwood Dynasty Adversely Affected by Consanguinity?
Ohio State University: Study: Darwin was right to worry that marriage to his cousin affected his offspring
Scientific American: Charles Darwin’s family tree tangled with inbreeding, early death