That’s because none of those talents arise from a single gene mutation, or even from an easily identifiable number of genes. Most human traits are nowhere near that simple.
“Right now, we know nothing about genetic enhancement,” said Hank Greely, director of the Center for Law and the Biosciences at Stanford. “We’re never going to be able to say, honestly, ‘This embryo looks like a 1550 on the two-part SAT.’”
Even with an apparently straightforward physical characteristic like height, genetic manipulation would be a tall order. Some scientists estimate height is influenced by as many as 93,000 genetic variations. A recent study identified 697 of them.
“You might be able to do it with something like eye color,” said Robin Lovell-Badge, a professor of genetics and embryology at the Francis Crick Institute in London.
But “if people are worried about designer babies, they’re normally thinking of doing special — different things than the normal genetic stuff.”
The gene-modification process used in the new study also turns out to be somewhat restrictive. After researchers snipped the harmful mutation from the male gene, it copied the healthy sequence from that spot on the female gene.
That was a surprise to the scientists, who had inserted a DNA template into the embryo, expecting the gene to copy that sequence into the snipped spot, as occurs with gene editing in other body cells. But the embryonic genome ignored that template, suggesting that to repair a mutation on one parent’s gene in an embryo, a healthy DNA sequence from the other parent is required.
“If you can’t introduce a template, then you can’t do anything wild,” Dr. Lovell-Badge said. “This doesn’t really help you make designer babies.”
Talents and traits aren’t the only thing that are genetically complex. So are most physical diseases and psychiatric disorders. The genetic message is not carried in a 140-character tweet — it resembles a shelf full of books with chapters, subsections and footnotes.