Wall Street Journal, March 3, 1997, p. A18
The recent cloning of a sheep by Scottish researchers — producing an offspring from the genetic material of a single parent — has prompted alarm among nonscientists and warnings from medical ethicists and researchers. Alarm may be warranted, but not because any human clones would be identical replicas of their parents, mirroring their selves in every way.
For one thing, personality and consciousness are not direct products of DNA. And, even more fundamentally, a clone’s genome–its complete set of genetic material–would not be identical to its parent’s. The reason is that the function of most DNA is to regulate the development of genes in the growing organism. This regulatory DNA creates a unique genome for each individual, even for those that have inherited DNA identical to another’s.
Another reason not to worry about human clones is that varying environmental influences on each individual continue after birth. For example, identical twins–those who share all their genetic inheritance — generally differ in their assertiveness; it is hard for both members of a pair to be leaders. There are even more remarkable examples of such differences. Interviews of twin pairs in which one is gay and the other straight often find that the gay twins report that they felt that they were homosexual early in life. Their heterosexual twins are often equally adamant about their sexual identities.
How is this possible? The answer is that environmental influences contribute to all personality traits, even those as fundamental as sexual orientation. Even those who argue for a large genetic component in homosexuality, like researchers Michael Bailey and Richard Pillard, find that only half of gay men who are identical twins have gay brothers.
It may seem surprising that the degree of heritability of such traits is still unclear. Consider alcoholism, the heritability of which has been researched for decades. This trait is widely claimed to be inherited, yet the heritability statistic calculated for alcoholism ranges from almost total identity (0.98 out of a possible 1.0) to zero and below.
How can a trait have a negative heritability? The standard calculation of heritability involves subtracting the co-occurrence of traits in fraternal twins–those who share on average only half of their genetic data–from that found in identical twins. This figure represents the degree of genetic influence on the trait, since the environmental influences on each twin in both types of pairs supposedly even out.
In 1992 researchers at two of the leading behavior genetics centers in America — at the University of Minnesota and the Medical College of Virginia — reported on the heritability of alcoholism in women, using the same definition of alcohol abuse and research design. The Minnesota group found zero heritability of alcoholism among women (they actually found a negative figure). The Virginia group computed a heritability figure of 0.56 out of 1.0. Obviously, we have a very long way to go in determining the genetic influence on personality with any precision.
But even if two identical twins should have the same drinking problems, both be homosexual and finish each others’ thoughts (a trick many twins perfect because others seem to appreciate it), they will have separate consciousnesses and remain separate individuals. They will not make the same choices, prefer the same kinds of lovers or mates, or function as mouthpieces for one another. Society must treat them as individuals.
When one end of this connection is a parent and the other a child, the discrepancies in experience and outlook will be quite a bit larger. So no need to worry that a cloned child would think or act exactly the way a parent does. We should think of the parent and child as individuals. To think that identical strands of DNA could ever create identical humans is to misunderstand badly both human nature and genetics.