Outrage was the general researcher and media response to the Chinese bioengineer He Jiankui's announcement last November that he had used CRISPR gene-editing technology to modify the genomes of several human embryos with the goal of making them resistant to HIV infection. The result was the birth of twin girls; one with the genetic modification in all of her body's cells and another whose body is a mosaic of modified and unmodified cells. He did certainly cut both scientific and ethical corners in applying CRISPR technology to human embryos. Happily, a preliminary study in June that suggested the He's modifications might shorten the twins' lifespans appears to be wrong.

Setting aside He's moral shortcomings, is it ever ethical to use CRISPR and other gene-editing technologies to modify the genomes of human embryos? Yes, argues Abertay University bioethicist Kevin Smith in the journal Bioethics. Smith addresses the question using a rigorously applied utilitarian ethics approach. He details recent advances in CRISPR gene-editing safety and concludes that the benefits of preventing heritable diseases already outweigh the risks of using the technology.

In his article, Smith deals with "several well‐rehearsed positions and arguments" against permitting parents to use CRISPR gene-editing to fix genetic flaws in their prospective offspring. These include "claims of unnaturalness, the alleged interests of embryos, questions of identity, fears of eugenics, and simply the 'yuck factor.'" Smith points out that critics once denounced in vitro fertilization (IVF) on the grounds of that it was "unnatural." Millions of parents have freely chosen unnatural IVF techniques to overcome their natural infertility. Some 8 million children have been born via assisted reproduction since the first IVF baby was born in 1979.

Some opponents argue using CRISPR would be unethical because embryos can't give their consent to being genetically modified. A requirement for prenatal consent is obvious ethical nonsense. No one has ever given their consent to be born much less to be born the specific complement of genes they bear. In addition, it's hard to imagine that a child will later feel morally aggrieved that his or her parents had prevented them from suffering a debilitating genetic disease. Providing parents with the ability to choose to prevent heritable disease and disability in their progeny using biotechnology is not to be equated with morally pernicious state-imposed eugenics. And lots of biomedical treatments and reproductive technologies have gone from yuck to yippee as their significant benefits became evident. CRISPR gene-editing will do the same.

Smith persuasively argues that not only would the early application of the technology improve the welfare of prospective parents and their progeny now, it will usher in a human germline genetic modification (HGGM) revolution that will greatly benefit future generations. As Smith explains, "The longer we wait until commencing the HGGM revolution and moving towards a world of increased utility, the greater will be the quantity of suffering accrued meantime through genetically influenced disease."

When should CRISPR and even better gene-editing technologies be made available to parents seeking to prevent genetic diseases in their offspring? Given that some folks are still spooked by He's announcement last November, Smith prudentially suggests that "we kickstart the next biomedical revolution by proceeding not immediately but within around 1–2 years to intervene in the human germline."

The revolution, however, may start sooner than that. Russian researcher Denis Rebrikov says that he hopes to gain permission in the near future from the appropriate authorities to gene-edit embryos to repair a gene that causes congenital deafness.