Fellows in the News

In 2013, scientists discovered a new way to precisely edit genes — technology called Crispr that raised all sorts of enticing possibilities. Scientists wondered if it might be used to fix hereditary diseases, for example, or to develop new crops.

One of the more intriguing ideas came from Kevin M. Esvelt and his colleagues at Harvard University: Crispr, they suggested, could be used to save endangered wildlife from extinction by implanting a fertility-reducing gene in invasive animals — a so-called gene drive.

When the genetically altered animals were released back into the wild, the fertility-reducing gene would spread through the population, eradicating the pests.

The idea appealed to conservation biologists who had spent decades fighting a losing battle against exotic species. Some labs began running preliminary experiments. But now, three years later, Dr. Esvelt wishes he hadn’t broached the idea.


His regret arises from a study that he and his colleagues published on Thursday on the preprint bioRxiv server.

They created a detailed mathematical model describing what happens following the release of Crispr-altered organisms. And they discovered an unacceptable risk: Altered genes might spread to places where the species isn’t invasive at all, but a well-established part of the ecosystem.


Dr. Esvelt’s study suggests that if one nation decided to release such genetically engineered mosquitoes, neighboring countries quickly would become part of the experiment — whether they liked it or not.

International negotiations might be required before such genetically modified mosquitoes were set loose. “That’s not a question for scientists to answer on their own,” said Jason A. Delborne, a social scientist at North Carolina State University and a member of the N.A.S. gene drive committee.

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