Designer babies or not? MIT scientist Steven Pinker has a fascinating essay on so-called designer babies in the Ideas section of yesterday's Globe. Pinker's bottom line: the prediction that embryos will be genetically engineered so that children will be smarter, taller, better-natured, or whatever is little more than futuristic hype. Genetics, he writes, is a whole lot more complicated than is popularly believed.

Yet Pinker places an oddly artificial limit on his own predictive abilities when he writes: "Not only is genetic enhancement not inevitable, it is not particularly likely in our lifetimes." In our lifetimes? Is that what we're really talking about? What about 100 years from now, or 500, or 1000?

Last year, University of California scientist Gregory Stock offered a very different view in his book Redesigning Humans: Our Inevitable Genetic Future. Stock concedes the difficulty and, ultimately, the futility of direct manipulation of genes -- although he doesn't rule it out entirely.

Instead, he focuses much of his attention on a truly mind-bending concept: artificial chromosomes that could hold genes that fight disease, enhance intelligence, and the like. Such an approach, he argues, would be both easier and safer than "germline" engineering, the term for manipulating genes so that the changes will be passed on from generation to generation.

By contrast, the Stockian approach would limit any changes to the individual on which they are made.

In one particularly fanciful section, Stock writes:

Human conception is shifting from chance to conscious design.... Imagine that a future father gives his baby daughter chromosome 47, version 2.0, a top-of-the-line model with a dozen therapeutic gene modules. By the time she grows up and has a child of her own, she finds 2.0 downright primitive. Her three-gene anticancer module pales beside the eight-gene cluster of the new version 5.9, which better regulates gene expression, targets additional cancers, and has fewer side effects. The anti-obesity module is pretty much the same in both versions, but 5.9 features a whopping nineteen antivirus modules instead of the four she has and an anti-aging module that can maintain juvenile hormone levels for an extra decade and retain immune function longer too. The daughter may be too sensible to opt for some of the more experimental modules for her son, but she cannot imagine giving him her antique chromosome and forcing him to take the drugs she uses to compensate for its shortcomings. As far as reverting to the pre-therapy, natural state of 23 chromosomes pairs, well, only Luddites would do that to their kids.

Is this where we're going? Is it a good idea? Who knows? But I do know this: although I would certainly not presume to argue with Professor Pinker, the changes that may lie ahead in generations to come are bound to be far more formidable than anything we can imagine happening "in our lifetimes."