Little Green Men

Little Green Men

Little Green Men

Science, technology, and life.
May 14 2008 7:53 AM

Little Green Men

The genetically engineered humans are here! The genetically engineered humans are here!

William Saletan William Saletan

Will Saletan writes about politics, science, technology, and other stuff for Slate. He’s the author of Bearing Right.

I didn't believe it when I heard the report was in the Sunday Times of London. This, after all, is the paper that butchered the gay sheep story and can't find any evidence to back up its disputed paraphrases of James Watson . But the original report, which the Sunday Times neglects to mention, turns out to have been published in a scientific journal, Fertility and Sterility . It's titled , "Genetic modification of preimplantation embryos and embryonic stem cells (ESC) by recombinant lentiviral vectors: efficient and stable method for creating transgenic embryos and ESC."


For those of you who don't have access to the pricey journal, the New York Times boils down the experiment: Scientists "put a gene for a fluorescent protein into the single-celled human embryo," and "after the embryo divided for three days, all the cells in the embryo glowed."

What's new in this experiment isn't genetic modification of humans. We've already done that in limited doses, through the same viral technique. What's new is that because this was a single-celled embryo, every cell it went on to produce, including egg and sperm cells, would (except for the  diploid-haploid transition, which gets complicated) carry the same genetic tweak. If the embryo were implanted and grew into an adult, its fluorescent gene would be passed down like any other. This is called germline modification. If you wanted to transform our species or give your offspring an advantage that persists through generations, this is how you'd do it.

Naturally, genetic watchdog groups are freaked out. Human Genetics Alert calls it a prelude to "eugenics" and "designer babies" and demands an " international moratorium on such experiments." The Center for Genetics and Society says it "could push us toward a GATTACA-like world" dominated by "the genetically enhanced ."

The scientists, based at Cornell University, offer several responses. First, they used no U.S. federal funds , so no legal restrictions were violated. Second, the gene conveyed no enhancements; it was just a green " marker " to help them see whether it was replicated in subsequent cell divisions. Third, the experiment "was done on an embryo that was never going to be viable ," due to pre-existing chromosomal defects. Fourth, they destroyed the embryo after five days, as required by a Cornell review committee.


The watchdog groups are alarmed because Britain's parliament is presently debating legislation to lift restrictions on human embryonic genetic modification. (See yesterday's post about the bill's pregnant-man loophole.) But proponents of the legislation point out that the law would still ban growing such embryos beyond 14 days or transferring them to a womb.

When you line up the points made by scientists and liberalizers, it's easier to understand what's really going on here. It's not that we're plowing unimpeded toward genetic engineering of children. To the contrary, we've drawn lines to prevent that: the 14-day limit and the no-implantation rule. What's going on is that by drawing these lines, we've created a zone where virtually no legal or moral rules apply. Look at the American and British treatment of cloning, and you'll see the same pattern. You can clone embryos, mix species, and engineer all you want, as long as you don't implant the embryos or grow them beyond 14 days.

Maybe this system will allow us to make important scientific discoveries and conquer diseases without crossing the lines we've drawn. On the other hand, maybe it'll turn embryos into a testing ground for techniques that we'll use for people-engineering when we're ready to go there. Or maybe we'll relax the rules a bit at a time, extending our techniques to more advanced embryos as we test and refine them. We'll tell ourselves that we're curing genetic diseases in the womb so that babies and their babies will be born healthy.

The argument for the latter scenario is that, far from being diabolical, the idea of loosening the 14-day rule makes a lot of sense. The Cornell scientists point out that genetically modified embryos "could be used to study how diseases develop" and that "in order to be sure that the new gene had been inserted and the embryo had been genetically modified, scientists would ideally need to grow the embryo and carry out further tests." The longer you grow the embryo, the more you learn.

How long could we grow genetically modified embryos if we lift the 14-day rule? According to the New York Times , "A spokesman for the National Institutes of Health said the Cornell work would not be classified as gene therapy in need of federal review, because a test-tube embryo is not considered a person under the regulations." Roughly speaking, U.S. law confers personhood at viability. That's five months or so. Plenty of time for good work to be done.

I don't mean to make this scenario sound imminent. But as we ease ourselves into the world of genetic engineering, let's notice what we're doing. We're chalking off a zone where the ethics of human manipulation don't apply, on the grounds that the human entities we're manipulating aren't human beings. Seven years ago, scientists and supportive ethicists set up a similar ethics-free zone based on origin : Human embryos produced by fertilization were protected, while those produced by cloning were fair game. Now we've shifted to lines based on age and location.

Will these lines hold? You can't dismiss the fear that they won't as slippery-slope nonsense from the anti-abortion crowd. Embryo research is fundamentally different from abortion. If you're a woman with an unwanted pregnancy, you have no incentive to prolong it. But if you're a scientist with an embryo modified for research, you have lots of good reasons to keep growing it and studying it. The only things holding you back are your conscience, your review board, and the law.

Here's my prediction: We won't end up extending species-mixing beyond the 14-day line. Nor will we end up deliberately growing embryos past that point for harvestable tissue, as I previously speculated . But we will extend germline genetic engineering all the way through pregnancy and beyond, and our grandchildren will wonder why it was ever controversial.