The recent announcement by Dr. Jeff Steinberg of the LA Fertility Institutes that they will soon be producing “designer babies” with chosen traits like preferred hair color or eye color has caused an uproar among “medical ethicists” and others throughout the world. The public reaction underscores another common misconception about science. Designer babies are nothing new. Contrary to popular belief, parents have been producing designer babies throughout human history.
First, the media portrayal of Dr. Steinberg’s announcement has not been entirely accurate. At the current level of knowledge of human genetics, fertility doctors can only accurately select embryos on the basis of sex and select out a very few genetic diseases (such as the Down syndrome or Huntington’s disease). Our current knowledge of human genetics is not sufficient to select babies for their eye color or hair color, because we don’t know the exact combination of genes that produce blue eyes or blonde hair. Nor has Dr. Steinberg made such a promise; he made no guarantees of perfect prediction of such traits as hair and eye colors. Nevertheless, bowing to public pressure, the LA Fertility Institutes have suspended their hair and eye color selection program as of 02 March, according to the clinic’s website.
Second, even if we have completely mapped out every single gene in the human genome and knew everything about which genes produce which phenotypic traits perfectly, “designer babies” will work only for traits that are 100% heritable. So if it turns out that eye colors are 100% determined by genes and the environment, even the prenatal environment in the womb, has absolutely no effect (which seems likely although we don’t even know that for sure yet), then we will eventually be able to select embryos on the basis of their genes to have hair and eye color of the parents’ choice.
However, even if we have perfect knowledge of the human genome, we still would not be able to create a “designer baby” on traits that have less than 100% heritability, such as intelligence, height, weight, and personality. For these traits, the best that hopeful parents can do is to increase and maximize the probability that their “designer baby” will have high intelligence or be tall. But since the genes do not determine these traits 100%, the parents cannot absolutely guarantee to have the designer baby of their choice. Selection will have to be done probabilistically, not deterministically with certainty of outcome.
The probabilistic selection of offspring traits is exactly what we and our ancestors have been doing for the entire human evolutionary history. That is why we do not mate randomly. We instead select our mates carefully, and we select them on certain traits that we (or, more precisely, our genes) consider important, whether or not we are fully conscious of what we are doing when we select our mates. Why do men prefer to mate with beautiful women and not with ugly women? It is partly because beautiful women are genetically and developmentally healthier than ugly women, and they thus make better mothers. But part of the reason is so that their children (especially daughters) will also be beautiful. Why do women prefer to mate with tall men and not short men? It is partly because big and tall men make better hunters and provide better physical protection of the women and their children. But part of the reason is so that their children (especially sons) will also be tall. The same goes for why we want intelligent and kind mates.
So humans (and other species) have always created “designer babies” with various probabilities of success, and this is nothing new. With the advances in the DNA technology, the probability of producing a baby with desired traits will likely increase, but it will never be guaranteed for most traits (those with less than 100% heritability). On the other hand, if a blonde, blue-eyed woman marries (or mates with) a blond, blue-eyed man, she is virtually guaranteed to have a blonde, blue-eyed baby, whereas if she marries (or mates with) a black-haired, brown-eyed man, she substantially reduces the probability of having a blonde, blue-eyed baby. The Swedes have been producing their “designer babies” this way for thousands of years now, and they never needed any DNA technology. Every woman who chooses to marry a tall, handsome, intelligent, kind, and hard-working man instead of a short, ugly, unintelligent, mean, and lazy man is in essence unconsciously and probabilistically creating a “designer baby.”
