Scientists adds human brain genes to monkeys

Scientists in China have created a new kind of monkey. It’s got a human brain gene. And that just might make its intelligence a little bit more like ours.

That, in turn, makes its fate — and its very existence — very ethically fraught.

In a study published last month in Beijing’s National Science Review journal, researchers took human copies of the MCPH1 gene, which is believed to play an important role in our brain development, and introduced it into monkey embryos by means of a virus that carried the gene.

Of the 11 transgenic macaque monkeys they generated, six died. The five survivors went through a series of tests, including MRI brain scans and memory tests. It turned out they didn’t have bigger brains than a control group of macaques, but they did perform better on short-term memory tasks. Their brains also developed over a longer period of time, which is typical of human brains.

Although the sample size was very small, the scientists excitedly described the study as “the first attempt to experimentally interrogate the genetic basis of human brain origin using a transgenic monkey model.” In other words, part of the point of the study was to help tackle a question about evolution: How did we humans develop our unique brand of intelligence, which has allowed us to innovate in ways other primates can’t?

The Chinese researchers suspect the MCPH1 gene is part of the answer. But they’re not stopping there. One of them, Bing Su, a geneticist at the Kunming Institute of Zoology, told MIT Technology Review that he’s already testing other genes involved in brain evolution:

One that he has his eye on is SRGAP2C, a DNA variant that arose about two million years ago, just when Australopithecus was ceding the African savannah to early humans. That gene has been dubbed the “humanity switch” and the “missing genetic link” for its likely role in the emergence of human intelligence. Su says he’s been adding it to monkeys, but that it’s too soon to say what the results are.

Su has also had his eye on another human gene, FOXP2, which is believed to have graced us with our language abilities. Pondering the possibility of adding that gene to monkeys, Su toldNature in 2016, “I don’t think the monkey will all of a sudden start speaking, but will have some behavioral change.”

He would not be breaking any laws. (In the US, scientists have created human-animals hybrids in an attempt to grow human organs for medical transplants — for example, by injecting human cells into a pig embryo and a sheep embryo — but such studies are not eligible for public funding.)

Su’s prediction that his tinkering would cause behavioral change raises a slippery slope concern: If we deem it acceptable to make an animal slightly more human-like, we may end up normalizing that process and find ourselves generating animals that resemble humans to ever greater degrees.