What’s the difference between genetic engineering and eugenics?

For a half-century, the ethics of human genetic engineering have been discussed in the abstract. Because the tools to edit DNA didn’t exist, the question was more a thought experiment than a real concern.

Today, though, the conversation has completely changed. There has been a frenzy of excitement around the possibilities of CRISPR-Cas9. The technology, which allows scientists to design proteins that unzip and replace chunks of DNA as they please, makes it possible to edit genes quickly and cheaply. Investors have poured hundreds of millions of dollars into the innovation, which seems to have endless possibilities: making crops more resilient to diseases, designing mosquitoes so they can’t carry malaria — maybe even eliminating diseases among humans by altering the genes we pass on.

Scientists are confident that the technology could one day eliminate genetic disorders in humans. However, the research is still very young, and there are major ethical questions attached to editing human DNA that the emergence of CRISPR makes even more pressing: Wouldn’t editing out inheritable traits from the human population simply amount to eugenics...