Human Genetic Diversity and the Threat to the Survivability of Human Populations

Christian Wolfe, Washington & Jefferson College

Ohio University Institute for Applied and Professional Ethics

Student Conference

April 26-27

wolfect@washjeff.edu

(724) 503 – 1070 Ext 7844

50 S. Lincoln St

Campus Box 1174

Washington, PA 15301

Abstract

Recent advances in reproductive technologies, especially those that alter the germ-line, raise many ethical and theological concerns. I address one of the pragmatic ethical concerns, the potential loss of genetic diversity. Since genetic diversity has an inverse relation with the survivability of populations, it is necessary to have strong evidence that the implementation of these technologies will not threaten the survivability of human populations. An examination of the genetic diversity argument (GDA) and the possible models under which the technologies would be distributed (free market and state control) reveals that there is not strongly persuasive evidence regarding the effects on genetic diversity of the reproductive technologies on human populations. The only available method to produce the required evidence is through a very complex form of human experimentation. The type of human experiment that would produce the evidence is incompatible with present ethical codes of conduct. Therefore, any implementation of these technologies on human populations should be banned.

Through advances in reproductive technologies humans will eventually have the ability to utilize nearly fully artificial selection on human populations. These technologies raise many ethical and theological concerns. I will address one of the pragmatic ethical concerns, the potential loss of genetic diversity. Genetic diversity has a direct relation to the fitness and survivability of various species and populations; as genetic diversity decreases within a population, so does the fitness and survivability of that population. An examination of the genetic diversity argument (GDA) reveals that there is not strongly persuasive evidence regarding the effects on genetic diversity of the reproductive technologies on human populations. The only method available to produce the required evidence is through a very complex form of human experimentation. The type of human experiment that would produce the evidence is incompatible with present ethical codes of conduct. Therefore, any implementation of these technologies on human populations should be banned.

There are many emerging technologies that could potentially affect genetic diversity. These include genetic testing and screening, selective breeding, population control, sterilization, selective abortion, embryo testing and selection, sperm donation, egg donation, embryo donation, surrogate pregnancy, fertility drugs, contraception, cloning embryos, and germ line or somatic cell manipulation (Resnik 2000, 454). Each of these reproductive technologies affects the composition of the human gene pool by increasing or decreasing the frequency of different genotypes or combinations of genotypes (Resnik 2000, 454).

The germ-cell line, or just germ-line, constitutes a cell line through which genes are passed from generation to generation (World of Genetics 322). Germ-line therapy is often differentiated from somatic cell therapy, which is the alteration of non-reproductive cells. This distinction is not as clear as much of the literature supposes, but the problems with the germ-line/somatic cell distinction are beyond the scope of this paper. The focus of this paper includes the screening of embryos with the possibility of destruction of certain embryos, the modification of DNA (deoxyribonucleic acid) of early stage embryos through in-vitro fertilization (IVF), and the modification of parent gametes (Zimmerman 594-5). These technologies pose the clearest threat to genetic diversity of human populations.

Genetic testing and screening examines the genetic information contained in a person’s cells to determine whether that person has or will develop a certain disease, is more susceptible to certain environmental risks, or could pass a disease on to his or her offspring (World 305). Parents could subject themselves to testing to determine whether or not to reproduce based on the likelihood of their potential children inheriting their genetic maladies. Also, embryos can be subjected to testing and screening to determine the likelihood that the future individual will develop a genetic disease. From that information, parents can decide to destroy the embryo, alter the embryo, or leave the embryo unmodified and risk that the child will develop a genetic disease.

Germ-line gene therapy (GLGT) is germ-line manipulation on the genetic level in order to prevent genetic diseases in future persons (Richter and Bacchetta 304). The goal of GLGT is to treat human diseases by correcting the genetic defects that underlie the genetic disorders (Anderson and Friedmann 907). Therapy presents an alternative to destroying embryos likely to develop genetic disease by actually correcting genetic defects. Also available is the alteration of parent gametes in order to eliminate the possibility of passing on genetic disease to their offspring. GLGT allows for the alteration of either the early stage embryo or the parent gametes to prevent genetic disease. By either eliminating those genotypes that are likely to produce genetic disease or by altering the genome to actually prevent the genetic disease from developing, these technologies have great potential to affect the genetic diversity of a population.

Genetic diversity is the variety and frequency of different genotypes or combinations of different genotypes within a population. A population is a geographically, socially, or culturally linked group whose reproductive decisions affect those within the group. Genetic diversity is measured by genetic variability, which diminishes in a population when the number of different phenotypes or the number of different combinations of genotypes decreases. Since populations are composed of individuals that carry genotypes, individual reproductive outcomes affect the genetic variability within specific populations (Resnik 2000, 452). Genetic diversity provides the resource for phenotypic variation that is integral in determining the rate of evolutionary change in an environment. A population that lacks genetic diversity will be poorly equipped to meet environmental changes and demands (Resnik 2000, 452). The importance of genetic diversity is undeniable; the survivability of a population is directly related to genetic diversity.

While genetic diversity has no intrinsic value, genetic diversity has a clear instrumental value. Humans place positive value in genetic diversity as it promotes the extrinsic value of survivability. There is an ethical duty to prevent decreases in the genetic diversity of populations because of its importance in the survivability of those populations. Decreases in genetic diversity in populations are ethically undesirable because actions that reduce the survivability of the population are unethical.

The genetic diversity argument (GDA) starts from the fact that scientific and technological developments in the realm of genetics and human reproduction will greatly affect the genetic diversity of human populations. There are both pessimistic and optimistic versions of the argument. I will briefly describe both versions of the GDA.

The pessimistic version of the argument contends that the increased ability to control human reproduction will result in a loss of genetic diversity that will threaten the health and survivability of human populations (Resnik 2000, 451). This threat to health and survivability is due to a decrease in the populations’ ability to adapt to environmental changes and demands. In effect, these technologies have the potential to make the pool of available phenotypic traits limited enough so that human populations will not be able to respond to changes in environmental demand.

This version of the GDA warns that germ-line altering reproductive technologies will reduce populations’ gene pools and eliminate potentially useful genes. Genetic diversity provides a resource of these useful genes. Evolutionary change is blind and has no way to know which genes are useful, therefore it is potentially damaging to population survivability to eliminate genes of any sort. As Glenn McGee notes, “The point of the GDA is that human beings also have no way of knowing which genes will be useful in the future or in different environments” (cited in Resnik 2000, 456). For instance, genetically homogenous populations of corn face problems with blight due to lack of genetic diversity. Although human populations have an ever-increasing level of control over the environment, the pessimistic response still turns on the inability to determine which genes will be useful in the future.

The optimistic version of the genetic diversity argument contends that these reproductive technologies could lead to increases in human health and survivability resulting in an improvement of the well being of populations (Resnik 2000, 457). The basis for this response rests on the historical fact that advances in technology increase humans’ ability to control nature. The ability to control nature often leads to positive changes in the adaptability and survivability of human populations. The optimistic GDA relies on this historical fact and the seemingly obvious inference that the above technologies will increase the ability to affect the genetic diversity of human populations (Resnik 2000, 457). A commonly cited example of how genetic diversity can be increased with the implementation of such technologies is the incredible diversity of canines. Of course, there are important dissimilarities such as the explicit intention to increase phenotypic diversity.

A major factor in whether these reproductive technologies will increase or decrease genetic diversity is what model they are implemented under, free market or state control. Each model addresses the concerns and motivations of those affected differently.

The free market model is based upon the reproductive decisions of a diverse group of potential parents with separate interests, motivations, and means. The free market is the method by which many consumer decisions are made in the United States. This model is fundamentally based on the interaction between supply and demand. If a market demands diversity of a product, then the market will often supply the desired diversity. If the market demands the standardization of goods, such as building supplies, then that homogeneity is likely to be supplied. Also, markets create new preferences and demands by introducing new goods and services to the market. Most often, advancements in technology increase market variability, except of course if that development results in the formation of a monopoly.

The diversity of goods in the free market system of America seemingly justifies the inference that a free market model for reproductive technologies would lead to increases, not decreases, in the genetic diversity of human populations. Both J. Glover and W. Gardner’s individual studies conclude, “Increases in our ability to control human reproduction will result in more genetic diversity in the human population because parents will have a variety of preferences and values that they can use in selecting offspring” (cited in Resnik 2000, 458). Just as technological advancements have increased the availability of diverse consumer products, germ-line altering technologies could increase the available options in reproduction and therefore increase the diversity of human populations. Nevertheless, confounding factors such homogeneity of desirable characteristics makes the above inference much more dubious than it first appears.

The major problem with the free market model is the potential emergence of the homogeneity of desirable characteristics. Many characteristics such as intelligence, athleticism, and health, are almost universally accepted as desirable. Other characteristics such as height, eye color, and hair color, also have particular value attached to them. Genetic homogeneity could arise if the consumers of reproductive technologies have similar preferences for traits. As Resnik states, “If most people want tall, intelligent, healthy children with blonde hair and blue eyes, then parental choices could produce a phenotypically and genetically homogeneous population” (2000, 459). This problem is only exacerbated when one considers the phenomenon of fads. Societal pressures and obligations may also produce conformity. While these social effects may not take hold immediately, it seems possible, if not probable that these pressures would eventually affect reproductive decisions. Genetic homogeneity may be an unintended consequence of a population sharing common values (Resnik 2000, 459). If most people within a population have similar characteristic preferences and a desire to conform, genetic homogeneity is almost inevitable.

Of course much of this line of reasoning depends on genetic determinism, which is incredibly naïve and misinformed. Environmental factors often play a decisive role in which phenotypes are displayed. If certain desirable traits, such as intelligence or health, were strongly linked to environmental factors regardless of genotype, then the inference from individual choices to phenotypic characteristics would be dramatically weakened (Resnik 2000, 465). On the other hand, if certain genes or series of genes are linked to a trait, and that genotype is most frequently selected, it would still poses the potential threat of a genetically homogeneous population, although not phenotypically homogeneous.

There are good reasons to believe that the free market system will create greater genetic diversity within human populations. On the other hand, the influences of societal pressures and expectations should not be underestimated or ignored (Resnik 2000, 459).

State control involves the local or federal government dictating the standards of practice in certain industries, such as the power industry, education, and mass transit. This model of control in implementing genetic technologies appears likely to lead to decreases in genetic diversity within a population. It is imaginable that the government would develop specific standards to which all human beings produced in that state would be subject. The effects of state control of reproductive technologies are not clearly predictable. A state controlled system could lead to a genetic caste system. For instance, if the state determined that all people should be a certain height, weight, IQ, color, sexual orientation, etc., then those who diverge from those state determined standards could be forced into different strata of the genetic caste system. Such scenarios are certainly plausible, if not likely under state controlled conditions.

Under free market conditions, reproductive technologies could lead to increases or decreases genetic diversity. On the other hand, state control would almost inevitably lead to decreases in genetic diversity, but the extent of such effects is not clear. As David Resnik claims, “the consequences of not exerting social or governmental control over human genetics may be just as troubling, since parents will in all likelihood attempt to provide their children with genetic advantages, and the long-term results of parental control over human genetics may further exacerbate existing social and economic inequalities and create a genetic caste system” (1997, 428). The inability to produce definitive evidence of the effects of reproductive technologies under either control model points to urgency of the issue and the minimal knowledge of these technologies’ implications for the future of humanity.

Each version of the GDA provides ground for arguments that could support or undermine the utilization of germ-line altering reproductive technologies. The most obvious conclusion from examining both versions is that there is no definitive evidence that implementing the above technologies will have positive or negative consequences for the survivability of human populations. Furthermore, an examination of the two most plausible options for methods of implementing the technologies within a population does not produce strong evidence that implementation will result in either increases or decreases in genetic diversity. This leaves medical science at an ethical crossroads between either continuing with the technologies and dealing with the results afterwards, or abstaining from research, or at least clinical trials, until such evidence arises. Neither of these paths seems to be positive, or even tenable.

The only method for producing clear evidence about the potential threat to survivability that these reproductive technologies pose would be to continue research and perform a massive clinical trial. Animal experimentation is not a viable alternative to human experimentation because it completely eliminates many of the confounding factors such as social influences. Since the arguments on either side of the GDA cannot produce conclusive results, and given the potential harm done to populations if the reproductive technologies are implemented and genetic diversity does decrease, some form of human experimentation seems necessary before the technologies should be implemented. Of course, there are many questions that arise in response to such a claim, including the justification of the inference to the necessity of human experimentation. I will discuss these concerns below.

To clarify the inference, one should be reminded of what is at stake with respect to genetic diversity. The cautionary tales of the GDA describe potentially analogous situations, such as the effects of artificial selection on the survivability of maize and the variety of canines that have been produced by artificial selection. It is not at all clear what effects the above reproductive technologies will have on a population’s genetic diversity. Their implementation could result in increases in disease susceptibility like the result of artificial selection on maize, or it could result in populations with incredible arrays of genetically distinct individuals, such as in the canine example. What is clear though is that genetic diversity has an inverse relationship with the adaptability and survivability of populations. Since human populations value their own survivability, it is clear that technologies that pose a great potential threat to genetic diversity should be closely examined before being implemented. Due to the great potential threat these technologies present to humans, it is necessary to produce very strong, if not definitive, evidence about the effects of these technologies on genetic diversity. The only way to produce such evidence is human experimentation.

There are many factors that must be accounted for in a human experiment that would produce definitive evidence. The number and diversity of subjects would have to emulate a population that would be affected by the technologies. The experiment would have to be extensive enough to determine the effects on future generations. To account for potential homogeneity of desirable characteristics, the experiment should account for both diverse cultural and societal pressures. Furthermore, the experiment should be carried out under the two control models mentioned above, free market and state control. Also, there would have to be a method of curtailing influences from the non-experimental population. Finally, in the event that something goes awry with the experiment, there must be a method of destroying the test subjects.

Given present ethical standards concerning human experimentation, the ethics of such an experiment are, at best, deeply problematic. While ethical norms can dramatically change with time through changes in societal norms and beliefs, the means necessary to employ such an experiment are almost incomprehensible. For instance, it is not at all clear how the experiment would quarantine the subjects or how to handle the necessity of multiple generations of researchers. The role of informed consent is unclear with such an experiment. In the proposed experiment, an unethical researcher could use informed consent in a manner to produce the results that the researcher desires and undermine the purpose of the experiment. Additionally, an integral part of informed consent is the ability to withdraw from the experiment at any time. This element could pose a serious problem for this type of research. Therefore informed consent must either be eliminated or be drastically altered. Under present ethical norms it is clear that the kind of experiment necessary to provide strongly persuasive evidence of the effects of germ-line altering reproductive technologies would be unethical. Ethical considerations aside, the pragmatics of such an experiment are daunting to say the least.

The use of germ-line altering technologies should not be implemented until strongly persuasive evidence regarding the effects on genetic diversity is concretely established. Decreases in the genetic diversity of a population would put at risk the survivability of that population. Humans place a clear value in the survivability of populations. Therefore anything that threatens the survivability of populations is unethical. Germ-line altering reproductive technologies may potentially decrease genetic diversity within a population. Until there is concrete evidence demonstrating that such technologies will not lead to decreases in a population’s genetic diversity, those technologies should not be utilized. The only method of assessment to produce such evidence is through human experimentation. The nature of the necessary experimentation involves unacceptable ethical violations and unavoidable pragmatic difficulties. Without strong proof that such technologies do not pose a threat to genetic diversity, and therefore population survivability, those technologies should not be implemented. Due to the fact that such evidence is not possible, germ-line altering technologies should be banned.

Works Cited

“Genetic Testing and Screening.” World of Genetics. Eds. K. L. Lerner and Brenda W. Lerner. 2 vols. New York: Gale Group, 2001. 305-309.

“Germ Cells and the Germ Cell Line.” World of Genetics. Eds. K. L. Lerner and Brenda W. Lerner. 2 vols. New York: Gale Group, 2001. 322.

Anderson, W. French and Theodore Friedmann. “Gene Therapy.” Encyclopedia of Bioethics. Ed. Warren T. Reich. Volume 2. New York: Simon & Schuster Macmillan, 1955. 907-914.

Resnik, David B. “Genetic Engineering and Social Justice: A Rawlsian Approach.” Social Theory & Practice 23.3 (1997): 427-49.

—. “Of Maize and Men: Reproductive Control and the Threat to Genetic Diversity.” Journal of Medicine and Philosophy 25.4 (2000): 451-467.

Richter, Gerd and Matthew D Bacchetta. “Interventions in the Human Genome: Some Moral and Ethical Considerations.” Journal of Medicine and Philosophy 23.3 (1998): 303-317.

Zimmerman, Burke K. “Human Germ-line Therapy: The Case for its Development and Use.” Journal of Medicine and Philosophy 16 (1991): 593-612.

This entry was posted in 2003 Conference, Bioethics and tagged , , . Bookmark the permalink.

Comments are closed.