Scientists have put a human brain gene into monkeys. Have they crossed the line?

A nightmare Planet of the Apes scenario, where intelligent apes displace humans, came to mind for many last week when a story broke out of China.

Scientists genetically modified rhesus macaque monkeys with a human gene thought to play a role in the development of our big brains.  

And many in the west believe this research crossed an ethical red line.

"The researchers were interested in what role genes played in human brain evolution," said Prof. Jim Tabery, a bioethicist and associate professor in the department of philosophy at the University of Utah in Salt Lake City, in conversation with Quirks & Quarks host Bob McDonald.

The human brain gene

About two to three million years ago, the fossil record shows our ancestors' heads started getting bigger, probably linked to an increase in the size of our brains.

"A number of genes in the past had been implicated in that story — genes that are responsible for neural development," said Tabery. "And so these researchers focused in on one of those [genes] and wanted to see what happened when you took the human version of that gene and put it in a relatively similar non-human animal: the macaques."

The gene in question is known as MCPH1, or microcephalin. It's in part responsible for neural development — something we know because babies with a dysfunctional version of the gene are born with tiny heads.

"Non-human animals have their own version of it," said Tabery. "Humans have more copies. And so, essentially what these researchers ended up doing was putting multiple copies of microcephalin — that humans have — into viruses. Then [they] infected the monkey eggs with those viruses, which got those human genes into the monkeys' genome."

The study was published in a Beijing journal, the National Science Review.

Results of transgenic monkey study

The study began with 11 monkeys, but six did not survive, leaving only five transgenic monkeys. These monkeys were then compared to five non-genetically modified monkeys

"[The transgenic monkey] brains were not any bigger than the monkeys that did not have the human genes," said Tabery. But he added that the study, which was published in a Beijing journal, the National Science Review, did find the transgenic monkeys did a "bit better on a series of short-term memory tests."

[The transgenic monkey] brains were not any bigger than the monkeys that did not have the human genes.- Prof. Jim Tabery, University of Utah

One other trait the Chinese scientists noticed in the monkeys is that their brains developed a bit more slowly.

Tabery explains: "We do know that human brains develop slower than other mammals. Human babies are dependent on their parents far longer than other similarly-sized mammals. And we think that's, in part, because their brains are developing slower, but then they get the more significant cognitive impact later."

Ethical concerns

For bioethicists like Tabery, the real worry is this kind of research where scientists are trying to humanize a non-human animal by making them more biologically similar to humans.

"The thought is you can keep doing this stuff to these non-human animals — as they get more and more human, but because they're not human, we don't have to worry about any of the ethical considerations that apply to [studying] humans. And that's just a really dangerous road to go down."  

He also pointed out that there are other weaknesses to this study that make it ethically problematic that these primates were used in this way.  The small sample size of only five animals means any results they found could be due to chance. 

This is not the first time human genes have been put into monkeys.  Scientists in the US created transgenic monkeys with the gene for Huntington's Disease. But Tabery suggests that in that case there was an obvious biomedical purpose. In the case of this new work, he thinks the ethical bar should have been higher. 

It's also not clear how much can be learned from a single gene study like this.  Human intelligence is thought to involve hundreds, maybe thousands of genes, which limits what scientists can really learn about human brain evolution by investigating one gene at a time.

Even though the study found relatively small effects, Tabery said it might have been worse had they found large effects.  The ethical challenge of dealing with a much more intelligent monkey would have been multiplied. 

"I think that's the real risk with this kind of research."

According to a statement from the Kunming Institute of Zoology of the Chinese Academy of Sciences, the research was approved by an ethics board and they followed international animal rights standards.