Last week we looked at whether it would be possible to clone Abraham Lincoln from the hair and blood samples preserved in a museum. Sadly, it wouldn’t (the DNA is probably too degraded). But the issue of cloning a celebrity brings up the age-old nature vs. nurture debate. How much of your personality is governed by your environment and how much do you owe to your genes?
In 2004, University of Virginia psychologist Erik Turkheimer declared, “The nature-nurture debate is over … All human behaviors are heritable.” Turkheimer’s studies of adoptees, siblings and twins show that the behaviors of people who share the same genes – but not necessarily the same environments – are oddly similar. A 1979 study by psychologist Thomas Bouchard supports Turkheimer’s claim. Bouchard compared scores from thousands of I.Q. tests and found that identical twins raised apart had a 76 percent correlation in I.Q. scores (very similar), while adopted children living together had a 0 percent correlation (very different).
In a recent article in The New York Times Magazine, cognitive psychologist Steven Pinker explored the genes that shape personality. Turns out genes play a huge part in human behavior, but our surroundings and desires can trump those genetic urgings. Pinker reported that while scientists can look at genetic sequences to predict your risk for diseases like Alzheimer’s, it is more difficult to pinpoint behavioral traits like intelligence. For example, in a recent study of 6,000 children, the gene found to have the greatest effect on I.Q. accounted for less than one-quarter of an I.Q. point.
Chemically-induced personality traits like depression are easier to track down. Scientists know that SERT, the molecule that reduces the amount of relaxing serotonin in the brain, is subject to genetic variation. The brain can produce two types of SERT, a long variation and a short variation, and a genetic switch controls which kind of SERT you get. People with the short SERT variation are more prone to depression and anxiety.
“Of course, genes can’t pull the levers of our brain directly,” writes Pinker. “But they affect the wirings and working of the brain, and the brain is the seat of our drives, temperaments and patterns of thought.”
So if Lincoln were cloned in 2010, would he still rock the stovepipe hat?
Maybe, maybe not. Depends who you ask.
Francisco Ayala, professor of biology and philosophy at UCLA, is well known for his research into evolutionary genetics. Ayala believes cloned Lincoln would be very different from original Lincoln.
“We are what we are as a result of the interactions between our genes and the environment,” Ayala said.
Ayala said that if he were to go and clone himself, baby Francisco’s personality would be shaped by his modern-day school, classmates, culture and environment in the womb.
“The individual that comes out would not be me,” he said.
The environment of the womb is an interesting factor to consider. Research shows that children with a low-birth-weight have an I.Q. about 4.9 points lower that normal-birth-weight children. We also know that pregnant women who take multivitamins can reduce their babies’ risk for birth defects in the brain and spinal cord. Lincoln was obviously healthy and intelligent, but these recent discoveries in prenatal care show that we are still learning about the environmental effects on genes.
On the other hand, some experts believe cloned Lincoln would be very similar.
Harold Holzer is a historian who has authored, co-authored or edited 36 books about the era of Lincoln. He believes a clone would share some traits with the original – that the strong personality that drove Lincoln was something innate.
He explained that when Lincoln’s stepmother first brought books home, Abe was fascinated. Here were Bible stories and a book of Aesop’s fables, yet despite this “nurture” factor, “there was a pilot-light burning already” in young Abe. Holzer said that while Americans today romanticize Lincoln’s humble origins, life in the woods of Illinois was unglamorously brutal.
“There had to have been some natural, extraordinary, God-given talent in him to enable him to survive that environment,” Holzer said.
Replace “God-given” with “genetically-linked” and Holzer sounds like many geneticists today.
Despite the data regarding similarities between twins, I agree with Ayala; environmental differences would produce a different man.
The new Abe Lincoln would be famous from birth, not because he did anything important, but because of his DNA, sort of like Suri Cruise. We would expect him to be a national symbol from day one. Wannabe politicians wouldn’t just want photo-ops kissing babies, they’d want photo-ops kissing baby Lincoln. Instead of the self-taught, modest lawyer of Lincoln-past, the new Lincoln wouldn’t have to work a day in his life. He’d have a McMansion instead of a log cabin.
This summer I was having dinner with some family friends when I learned that one of them, a man named John, was a direct descendant of Abraham Lincoln’s aunt. Suddenly, I saw it: John was the spit ‘n’ image of Honest Abe. Same eyes, same cheek-bones. It was crazy. Here were Lincoln’s genes, walking and talking in front of me.
I started watching for Lincoln’s personality – the quiet reserve he was known for. And sure, John wasn’t a loud-mouth, but did he pick that up through his environment or from his genes?
Geneticists would like to find out, but analyzing the three billion nucleotide pairs of the human genome takes time. Then again, no matter the combination of upbringing and genes, at least you can keep blaming your parents.
MADELINE McCURRY-SCHMIDT likes the image of baby Lincoln in a stovepipe hat. In fact, all babies should wear stovepipe hats – just to be cute. E-mail Madeline at firstname.lastname@example.org.