Web Links

After you read the above named box in your text, and the accompanying "Check it out!" question, go to http://www.nichd.nih.gov/publications/pubs/counrs/sub3.htm for research highlights about reproduction and assisted reproduction technology, from the National Institute of Child Health and Human Development.

After you read the above names box in your text, and the accompanying "Check it out!" question, go to http://www.ornl.gov/hgmis/resource/medicine.html The focus of this Human Genome Project Web site is "Medicine and the New Genetics." Information about disease diagnosis and prediction, disease intervention, genetic counseling, and ethical, legal, and social issues is presented.

Now that scientists have successfully cloned animals, cloning human beings seems the likely next step. Will we soon be able to duplicate a Mozart or an Einstein? Do scientists have the right to "play God" with human life and personality?

Perhaps the most familiar use of cloning is in horticulture: gardeners reproduce a plant specimen valued for its vigor or beauty by taking cuttings from the mature plant and letting them take root. Cloning human beings would be much more complicated. An ovum would have to be removed from a woman's body and placed in a test tube. Its nucleus would be replaced by the nucleus of a body cell from the person to be cloned--a cell that contains all the paired chromosomes present in a zygote. After cell division begins, the resulting blastula would be implanted in the uterus of a woman, who would, in due time, give birth to an infant endowed with the same genetic makeup as the donor of the nucleus.

The ability to replicate human beings offers intriguing possibilities. In the broadest terms, the conscious selection of individuals for cloning might raise the genetic level of the human species. On a personal level, it could give infertile couples, or those in which one partner has a risky genetic profile, an additional option for producing a child genetically related to at least one of them. Or a couple might choose to clone existing offspring, a dead or dying parent or child, or one who needs a tissue or organ transplant but lacks a suitable donor.

These potential uses raise concerns so troubling to some people that the U. S. Congress has debated proposals to ban human cloning. The chief ethical issues involve the sanctity and dignity of human life. Opponents of cloning argue that it would devalue human beings by depriving them of their uniqueness and treating them as "interchangeable commodities" (Annas, 1998, p. 123).

Others see a clone as not much different from a later-born "identical" twin, raised by the older "twin" and his or her spouse. Such relationships might involve novel challenges, but it is argued that these challenges could be met through regulations requiring informed consent and counseling for the couple, guarantees of parental rights and responsibilities, and--to discourage commercial uses of cloning--a limit on the number of clones derived from any particular individual (Robertson, 1998).

Both the potential motives for cloning and the arguments against it may reflect a misunderstanding of the role of genes in human development. Although cloning can produce identical genotypes, it cannot produce identical phenotypes. Like monozygotic twins, clones would not look, feel, be, or act exactly like their genetic donors--in fact, even less so, since they would develop in different uterine environments and would grow up in different circumstances. Even physical appearance can be affected by prenatal experiences, such as the way a fetus is attached to the placenta and the substances it absorbs from the mother's blood (Eisenberg, 1999). Brain development, both before and after birth, is highly dependent on a combination of maturation and experience. And such complex characteristics as intelligence and personality hinge on a virtually inseparable intertwining of nature and nurture.

Thus, "to produce another Wolfgang Amadeus Mozart, we would need not only Wolfgang's genome [genetic makeup] but his mother's uterus, his father's music lessons, his parents' friends and his own, the state of music in 18th century Austria, Haydn's patronage, and on and on. . . . We [cannot assume] that his genome, cultivated in another world at another time, would result in the same musical genius. If a particular strain of wheat yields different harvests under different conditions of climate, soil, and cultivation, how can we assume that so much more complex a genome as that of a human being would yield its desired crop of operas, symphonies, and chamber music under different circumstances of nurture?" (Eisenberg, 1999, p. 474).

Indeed, instead of improving the human species, widespread cloning might have a negative effect. It might limit the adaptability of the human gene pool by emphasizing characteristics (such as Mozart's musical ability) that have been successful in particular environments but might turn out to be less successful in other, unforeseen circumstances. "Social evolution demands new types of men and women. Cloning would condemn us always to plan the future on the basis of the past" (Eisenberg, 1999, p. 473).

For more information on this topic, go to http://www.genome.gov/ top.html This is the Web site for the U.S. Human Genome Project.

How much difference do parents make in the way their children turn out? This question has caught the public imagination again and again--recently, for example, with Judith Harris's (1998) bestselling book The Nurture Assumption: Why Children Turn Out the Way They Do. It's a subject on which many developmental scientists strongly disagree.

Sandra Scarr (1992) http://www.dushkin.com/connectext/psy/ch08/bio8b.mhtml argues that being reared in one family rather than another--as long as the family is not violent, abusive, or neglectful--makes little difference in children's development. Diana Baumrind (1993), http://www.devpsy.org/teaching/parent/baumrind_styles.html on the other hand, maintains that parenting practices can and do influence children's lives. Jacquelyn Faye Jackson (1993) expresses concern that Scarr's view will harm children who need special help, by giving policymakers less reason to support interventions. Let's see how each of these researchers supports her view.

Scarr's Thesis: "Good Enough" Parenting is Good Enough

Most families provide supportive environments for their children. It does not matter whether parents take children to a ball game or to a museum, since children's inherited characteristics will outweigh such environmental influences.

Twin studies and adoption studies have found a strong genetic influence on differences in intelligence and personality. "Parents do not have the power to make their children into whatever they want" (p. 15); children to a great extent create their own environment on the basis of their genetic tendencies. If the environment is varied enough so children can choose experiences that fit their inborn tendencies, the athletic child will end up playing ball and the artistic child will create, no matter what their parents do. This is not, of course, true of children in "very disadvantaged circumstances and adults with little or no choice about occupations and leisure activities" (Scarr, 1992, p. 9). Among environments that support normal development, however, variations in parenting are not very important in determining outcomes.

One reason developmentalists have overemphasized the role of the family environment is that parents also provide children's genes, and so genetic and environmental influences are correlated. Parents who read well bring books into the house, read to the child, and encourage reading. Parents with reading problems raise children in a less literate environment. When children's reading abilities are correlated with their parents' abilities, the effects of heredity can be confused with the effects of the environment.

Since ordinary parents are good enough, they can take comfort in raising their children in ways that are comfortable for them without feeling guilty when they do not conform to current wisdom about good parenting.

Baumrind's View: Excellent Parenting Is Better Than "Good Enough"

All nonabusive, nonpoor families are not alike in fostering healthy development. The person a child will become in one "normal" environment is different from what the same child would become in another.

Scarr fails to specify what kinds of environment are "good enough" or what constitutes "normal development," making it hard to evaluate her thesis. She also fails to explore cross-cultural differences.

Many American children today--from both poor and well-off families--are growing up at risk of violence, drug abuse, poor reading and math skills, eating disorders, school failure, and sexually transmitted disease. "Thus, the average environment of most young people today is not really good enough" (Baumrind, 1993, p. 1302).

Biology is not destiny. Parents affect children's development by teaching knowledge and skills, monitoring children's activities, and modeling desirable behavior. All these practices take a high level of parental involvement and commitment, not just "good enough" parenting.

Scarr's thesis is dangerous because it may encourage parents to deny responsibility for children's healthy development. Parents who ascribe a child's dysfunctional behavior to the child's genes rather than to anything the parent did or did not do are less likely to try to improve the situation, and the child is less likely to turn out well.

Jackson's View: Interventions Can Be Effective

Research based on studies of twins and adopted children -- who are atypical in important respects -- cannot adequately support a theory about the development of "normal" children raised in "average" family environments. Scarr's theory can harm disadvantaged minority children by discouraging intervention to improve their environment. Interventions have been beneficial in boosting IQs of children of mothers with low IQs and in helping children with Down syndrome learn higher-order thinking skills.

Scarr's Response

"Both biological and environmental explanations are required to account for human development" (1993, p. 1334). What is normal for a given culture is not the same as what is normal for the human species; cultures define what behavior is desirable and provide a range of opportunities for development. But, because of their genetic makeup, different people--even siblings within the same household--react differently to the same environment. Biology and culture together shape behavior.

"Genetic does not mean intractable!" (p. 1350). Minority and socially disadvantaged children do benefit from interventions that transmit values of the dominant culture. Still, this does not negate the strong effect of inherited characteristics.

It is important to recognize the power of heredity and not to bend scientific truth

to a social agenda. "All children should have opportunities to become species-normal, culturally appropriate and uniquely themselves. . . . But humanitarian concerns should not drive developmental theory" (p. 1350).