Genetic engineering—when properly controlled—can enhance and lengthen human life.
DISCUSSIONS OF HUMAN GENE modification and gene enhancement tend to divide people into two camps: those bitterly opposed and those overwhelmingly in favor. Many opponents are thinkers who hold conservative religious beliefs. At the opposite extreme are the gene enthusiasts, who look forward to every new possibility as a sign of human creativity. Some of the enthusiasts are scientists, such as DNA co-discoverer James Watson and UCLA biophysicist Greg Stock. Others identify themselves as "transhumanists" who look forward to a day when we will mold our biology as readily as we do plastic or steel.
Human gene modification has the potential for great personal and social harm if it is introduced carelessly and allowed to proceed untended, but sooner or later we will begin to modify our genes, and we will survive doing so. I believe we are capable of bringing intelligence- "design" in the best sense of the word to our reproductive lives. Eventually we will grow accustomed to a world where human beings will use genetics to be physically and mentally better than they are today.
To put this view in perspective, consider how far we have come without genetic self-modification. Two centuries ago human beings died at an average age of about 40, many people suffered from the effects of serious ailments such as polio or tuberculosis and others bore obvious deformities, from disfiguring skin lesions to clubfoot or cleft palate. Modern medicine has changed all that, extending life spans and eliminating many physical and cosmetic problems.
According to Robert W. Fogel, a University of Chicago researcher on economic and population trends, new studies show that many chronic ailments, such as heart disease, lung disease and arthritis, are occurring, on average, 10 to 25 years later than they used to. There is also less disability among older people today. Thanks to better nutrition, disease prevention and treatments, says Fogel, humans in the industrialized world have undergone "a form of evolution that is unique not only to humankind, but unique among the 7,000 or so generations of humans who have ever inhabited the earth." In the future genetics will help us continue this trajectory.
Behind much of our opposition to directed human evolution lies a subtle form of status quo bias: the belief that the human genome in its present form represents the highest expression of human biological possibility and must not be tampered with in any way. While those who hold this view imagine cultural changes in the future that may take human civilization to higher levels, they generally believe that, at least in terms of genes, our biological nature has advanced as far as it can go. Leon Kass, former chairman of the President's Council on Bioethics, has said, "Man is the peak, both in possessing the highest, and also in possessing the complete range, of faculties of soul....The story of the ascent of soul may already be complete." This view, sometimes supported by appeals to religious texts such as the Book of Genesis, has little theological or scientific foundation.
There is nothing in our religious traditions that prohibits human beings from improving on nature, including their genetic inheritance. Throughout the Bible human beings are seen as Gods "co-creators," capable of introducing animal husbandry, medical arts and other technical innovations. Modern religious traditions carry forth this perspective. In a 1982 discourse Pope John Paul II explicitly approved the use of gene therapy to "ameliorate the condition of those who are affected by chromosomic diseases."
Nor does science support the view that the human genome is a stable and finished phenomenon. Genomic research provides evidence that the human genome has continued to evolve rapidly beyond the appearance of anatomically modern human beings about 200,000 years ago. Some of the change involves disease resistance. For example, when human beings started clearing African forests about 10,000 years ago they created an environment for malaria-bearing mosquitoes. In short order the disease spread, and natural selection responded by leading to the proliferation of human gene mutations that enhanced peoples malaria resistance. In Europe it appears that a similar process worked in response to smallpox epidemics as recently as 1,300 years ago.
Not all the changes involve disease resistance. Throughout history most human beings stopped drinking milk soon after being weaned from their mothers, and the genes that permitted them to digest milk sugar (lactose) were turned off. In cultures that are not milk-dependent, the turning off of these genes still produces adult lactose intolerance. But about five or six thousand years ago human populations in northwestern Europe became heavily dependent for survival on whole milk derived from domesticated cattle. In northern Europe (and in some cattle-raising regions of Africa) people with mutations in lactose-digesting genes survived and those who could not process this essential food died. Today, in most of Europe and America, we take it for granted that a glass of milk a day is good for you, but that is only because we are part of a newly evolved type of humanity.
In September 2005 the prestigious journal Science carried two articles that took the recent nature of human evolution and its significance to new levels. The articles detailed findings by teams led by Bruce Lahn, a human geneticist at the University of Chicago, including evidence of mutations that occurred about 37,000 years ago in a gene known as Microcephalin. This gene controls the number of neurons produced during fetal development. Individuals with seriously impaired versions of it suffer from microcephaly, a birth defect characterized by severe reductions in brain size coupled with mental retardation. But mutations found by Lahn's team seem to have had the opposite effect. By increasing brain size or function they conferred a selective advantage on those possessing them. In a relatively short time the mutations were widely prevalent. A second study found an even more recent mutation in another gene that regulates brain size known as ASPM.This occurred about 5,800 years ago and spread rapidly by natural selection.
These two articles raise many questions. Are these genetic changes related to historical and cultural shifts? The report on the Microcephalin gene, for example, points out that the dating for the novel mutation corresponds to the start of what archaeologists call the "upper Paleolithic revolution," which was marked by the appearance of striking new uses of symbolism, including statuettes and cave paintings found at many sites in Europe. The time of the ASPM change roughly correlates with the rise of cities and spread of written language. Although neither article suggests causation, together they raise the possibility that these cultural changes may have been initiated or accelerated by changes at the genetic level.
Like all science, Latin's teams' findings will remain tentative and suggestive until they are replicated and their implications are better understood. But when combined with the other, less controversial discoveries of the sweeping genetic changes in populations I've mentioned, they offer us a new way of viewing the human genome. It is not the stable, onceand-for-all achievement that many have tended to believe. We are not necessarily at the pinnacle of biological creation, as we have often thought. Just as our physiology and neural architecture may differ from our not-so-distant ancestors, so the biology of our descendants may lead them to look, act and think differently than we do. What nature accomplished in the past by natural selection, we may do by direction. Emerging genetic technology permits us to replace the destructive and wasteful process of natural selection with intelligence and design.
If we are to achieve a transformed but recognizably human future, we have to avoid the realization of our nightmares. We have to find ways of monitoring and moderating our steps to avoid the dangers. The genetic enhancement of human traits and capacities will not be possible for a long time, and the most complex traits, such as intelligence and temperament, may never be fully subject to control, but there are good reasons for starting to think about these possibilities. Advances that were almost unthinkable just a few years ago are now routinely being deployed in laboratories around the world. New microchip technologies, the unraveling of a host of mammalian genomes, including our own, and the ability to precisely insert genetic changes into organisms all work together to vastly augment our powers. Each development in one sector speeds breakthroughs in others, and some advances have already reached the clinic. In the past two years British medical authorities have authorized the use of in vitro fertilization, genetic analysis and embryo selection to help families avoid passing on genes associated with breast cancer.
Babies by design are in our future.While some will try to prevent this fromever happening, others want unfetteredfreedom to experiment. The challenge isto find a middle way. The time to starttalking about this challenge is now.
We are not necessarily at thepinnacle of biological creation,as we nave often thought.
RONALD M. GREEN is professor for thestudy of ethics and human values and directsDartmouth's Ethics Institute. His most recentbook is Babies by Design (Yale UniversityPress, 2007), from which this has been adapted.