Course title: Issues in Applied Ethics
Date: April 2006
Introduction
Cloning technology was one of the breakthroughs in genetics and reproduction biology in the last century. It ignited debate as well. Some voices went straight to prohibit this research. The safety issues were being questioned. Some fears were about human dignity. The latest controversies were about the South Korean biomedical scientist Hwang Woo-Suk. He reported that he created human embryonic stem cells. Indeed, it was a fraudulent claim. He was dismissed from Seoul National University last month.
In this essay, I outline several main ethical problems surrounding this issue. I also attempt to enquire the permissibility of this technology.
Here is the flow of this essay. First, I will give a brief description of cloning. Then, a central argument behind the debate, acting naturally or unnaturally, will be discussed. The Principle of Agency will be introduced in this section. Afterwards, I will turn to look at the purpose of cloning and suggest that if cloning is beneficial, it is permissible to act even if it may be unnatural. Next, I will stress some concerns about human cloning. They are personhood and uniqueness, genetic diversity and the misuse of cloning technology. Last but not least, animal cloning will be mentioned.
What is cloning?
In order to avoid confusion, it is essential to describe what I mean by cloning. Cloning may have different meaning in different context. Basically, "the asexual reproduction of plants, the budding of yeast in beer, the formation of identical twins and the multiplication of cells to repair damaged tissue in the normal process of healing" can be regarded as cloning. Also, "cloning techniques in plants have been in widespread use for centuries in gardening and crop development" (House of Representatives Standing Committee on Legal and Constitutional Affairs, 2001, p.18). However, they are not the concern of this essay. I rather focus on cloning through artificial technologies. House of Representatives Standing Committee on Legal and Constitutional Affairs state that DNA, cells, tissues, organs and even the whole individuals can be cloned. It is worthwhile to note, "cloning does not necessarily mean the replication of an entire individual" (2001, p.18).
There are two major cloning technologies: somatic cell nuclear transfer, and the isolation and characterization of human embryonic stem cells. To demonstrate somatic cell nuclear transfer, consider the Dolly experiment. Dolly the sheep was the first successful cloned mammal. In the experiment, a somatic adult cell was fused, by an electric pulse, with a nucleus-removed egg. The fused cells formed an embryo. The embryo is then transferred to the uterus of another sheep. Dolly the sheep was born after a normal pregnancy. She was the only sheep born after 277 attempts and the failures "resulted in abnormal placentas and fetuses and other complications during pregnancy or at birth" (2001, p.19-20). The second technique is embryonic cloning. An early pre-implantation embryo is taken. The embryo can be separated and each part will grow into genetically identical fetuses. Consequently, more embryos can be obtained for later use (Holland, 2003, p.192).
Natural VS unnatural
Some people hold the view that "it is ethically unacceptable to alter a species genetically." On the other hand, as Wilmut points out, we are using this technology widely (1998, internet). This is indeed the argument over nature. Some people maintain that artificial manipulation of genes is unacceptable, while the others do not. In this section, I will discuss this problem in general.
Holland presents the argument from nature and rejects it. Take homosexuality as an example. It is attacked as "unnatural" and Holland defends by saying "it's an expression of some people's natural (in the sense of being bestowed rather than chosen) sexual preference." Moreover, what is natural may not be good. Holland further questions that if the natural is defined as opposite of human artifice and manipulation, then isn't everything unnatural? For example, it is unnatural to put up an umbrella because we interfere the natural tendency of rain (2003, p.152-153). Holland's argument seems convincing. He gives examples on how is natural bad and how does human being acts unnaturally. But then, the opposite side may also give examples on how is natural good and how do we act naturally. What is natural is sometimes good and sometimes bad. Hence, the argument from nature should not be overthrown universally yet. It is crucial to look at particular situation.
Rachels proposes the Principle of Agency:
This sounds plausible. According to Rachels, a challenge to this principle is that it is a consequentialist principle and consequentialism is controversial. So Rachels goes on to explore the problem. A central argument is about intentions. There are two views of intentions: the direct effect view and the indirect effect view. In the former view, the same act may be right when done with one intention; and may be wrong when done with another intention. In the latter view, "actions done with different intentions are different actions." So, the morality of the action depends on intentions. Rachels claims that if you found trouble with the direct view, you would simply replace "to act so" by "to act with intention" in the principle. He then moves on to talk about rights. He states that there is no conflict between the Principle of Agency and rights. It is unlikely that we violate anyone's rights by acting to bring about the good (1998, p.154-160).
The Principle of Agency is convincing. It is permissible to act if the intention is good. This is equivalent to good intention is a sufficient condition to act. Consider taking medicine as an example. If one is sick, one will probably take medicine. Taking medicine is unnatural because it attacks the nature that one is sick. But he takes medicine because he wants to overcome the sickness and this is good for his health. Thus, acting unnaturally should not be forbidden. We should ask what is the purpose of the action instead. This leads to the next question: what is the purpose of cloning?
What for?
By analyzing Stephen Holland and James Rachels' arguments, we have seen the discourse upon natural and unnatural. Applying to the case of cloning, whether or not artificial manipulation of genes is acceptable depends on the purpose. The crucial question is: why do we need cloning?
John Harris describes several potential applications. I will outline them as follows. First, cell nuclear replacement (CNR) can be applied to cell therapy. The key is that "embryonic stem cell (ESC) have the capacity to differentiate in all human tissues (except for extra-embryonic)," that is to say, any damaged or fault part of our bodies can be repaired or rebuilt with the help of ESC. Also, there won't be shortage of tissues and immunological rejection anymore. Second, compatible organs can be created. This solves the problem of shortage of organs. The third one is about the treatment of mitochondrial disease (2004, p.6-8). These applications are permissible, given that it significantly benefits human beings.
Harris gives the fourth application that an embryo can be cloned or created for the purposed of research (2004, p.9). This is often controversial. Should we consider an embryo as a human being? Or we may put it like this: does the early embryo have moral status? Some authors refuse creating embryos for research (for example, see Holland, 2003; Keenan, 2001, p.67). While the others find it permissible. For instance, Campbell premises uses of embryos as research resources, but ethical justification should be taken into account (2001, p.47).
It is worthwhile to discuss why using an early embryo in research is permissible. Peter Singer states that if we reject medical advances because they are unnatural, then we have to reject the modern medicine entirely (2001c, p.536). This is similar to the point I made in the last section. Singer then attempts to answer the question. When does an embryo acquire rights? He proposes that we cannot harm the embryo until it has the capacity to feel pain. The embryo has the potential to become a person. But before the embryo turns to a sentient being, it has not been harmed even if we damage it. Controls should be taken into consideration only when the embryo is capable of feeling. Singer argues that an embryo can be used for research before "it has formed a brain and a nervous system" (2001c, p.539-540).
Another challenge is that the embryo has potential to become a human, so it is morally significant. Harris opposes this view. He claims that an embryo does matters when it had undergone changes. The following example is given. All human beings are potentially dead, but we do not treat anyone as dead beings. Furthermore, the egg and the sperm have potential to become an embryo, and that an embryo has potential to become a human. If we had to regard everything, which has potential to become a human being, morally significant, then we would be exhausted. Even if we assume that only the fertilized egg has potential to become a human, it is not so morally important (1998, p.50-52). Overall, if medical advances are beneficial to human beings, it is permissible to create and use early embryos in research. As Harris states, embryo research improves in vitro fertilization. More importantly, it helps to save lives (1998, p.59-60).
So far, I have discussed the concern that cloning is unnatural and suggested that it may be resolved by considering the purpose of cloning. If it has positive benefit, it is permissible to act unnaturally.
Concerns and worries about human cloning
This section discusses several concerns and worries about cloning. They are personhood and uniqueness, genetic diversity and the misuse of cloning technology.
It is claimed that cloning may lead to loss of personhood. Does it really matter? Technically, the cloned person is genetically identical to the person being cloned. That is it. Like twins, cloning will not produce identical person (Gillon, 2001, p.190; Harris, 2004, p.45-46). What makes a person unique? Genes, consciousness, memory, mental features and the body may be taken into account. But the gene itself does not matter, given that the cloned person and the person being cloned are two individuals. Growing up in different environment probably makes different persons. How a person thinks depends on what he already knows. It can be shown that prior knowledge affects perception and learning greatly. Personhood is far from being affected by genetic identity even at the beginning stage. Therefore, the cloned person does not violate the rights of anyone, nor can he cause others to lose their personhood.
Genetic diversity is another concern. Evolutionary biology tells us that genetic diversity is good to protect human beings from diseases. It is argued that cloning limits this genetic progress. This critic assumes that cloning will be a mass production. This is unrealistic (Brock, 2001, p.112; Harris, 2004, p.50; Pence, 2004, p.82-83). There is a general worry that if human beings took control of something, the consequences would possibly be bad. Rachels illustrate this worry with the following examples. "If euthanasia is permitted, we will end up killing the inhabitants of retirement homes; or if cloning is permitted, there will be rooms of artificially-created people silently growing spare parts." People tend to feel that the only way to prevent bad consequence is prohibiting the whole action. Rachels comments that it is slippery slope and the worries are less fundamental issues (1998, p.154-156). Nonetheless, have we underestimated this problem? Imagine millions of Albert Einstein or Adolf Hitler are hanging around. To prevent this, something has to be done.
If technology improves human life, it should not be banned. Of course, cloning technology has both advantages and disadvantages. The point is, how do people use it? As Mary Warnock puts it, "control should not be over research, but over the uses of research" (2001, p.233). The concerns mentioned above focus on the misuse of cloning technology. After the birth of Dolly the sheep is announced in Nature, the public worries about human cloning. Warnock insists "to legislate in such circumstances, in response to popular feeling, is almost always a mistake." Meanwhile, scientists are not absolutely free to do whatever they want. Also, the parliament and general public are ignorant of scientific research. So scientists should report the facts and probabilities to the public. Then judgment is made. Although legislation may not be necessary, regulation should be imposed. Scientists, practicing doctors, lawyers, philosophers and level-headed persons form a committee of inquiry. They should also seek public opinions before making moral judgments. The most important is "anonymous departmental civil servants – even if, as one hopes, they are strictly impartial and not under pressure from their ministers - cannot take on the educative role that is necessary in such cases" (2001, p.234-236).
Animal cloning
In the last section I focused on human cloning. Now I turn to discuss animal cloning.
How should humans treat animals? First, as Peter Singer states, "the principle of the equality of human beings is not a description of an alleged actual equality among humans: it is a prescription of how we should treat human beings" (2001a, p.275). He also fights for animals. He suggests that moral principles should be extended to animals (2001a, 2001b). It sounds reasonable to treat human beings and animals fairly. But what if human rights and animals right conflict with each other? I urge that there is a priority. Human beings are more important than non-human animals. I am not allowing anyone to cut a mouse's leg off and make it run for the purpose of his enjoyment. The point is, when two rights conflict, decision has to be made.
Now return to the question that when is animal cloning permissible? Or generally, can researches on animals be justifiable? We may, as Peter Singer advises, treat the animal as a brain-damaged human being (2001a, p.279). The basis is, if certain experiment on humans is allowed and human rights are not violated, then the experiment on nonhumans is also allowed.
Conclusion
My claim in this essay is that cloning can be ethically permissible under certain circumstances and such technology needs not to be banned. The crucial point is that if cloning is beneficial to human being, it is permissible. Particularly, say, embryo researches are allowed because they help to advance medicine. Pain and suffering of any sentient being should be prevented.
Cloning technology was one of the breakthroughs in genetics and reproduction biology in the last century. It ignited debate as well. Some voices went straight to prohibit this research. The safety issues were being questioned. Some fears were about human dignity. The latest controversies were about the South Korean biomedical scientist Hwang Woo-Suk. He reported that he created human embryonic stem cells. Indeed, it was a fraudulent claim. He was dismissed from Seoul National University last month.
In this essay, I outline several main ethical problems surrounding this issue. I also attempt to enquire the permissibility of this technology.
Here is the flow of this essay. First, I will give a brief description of cloning. Then, a central argument behind the debate, acting naturally or unnaturally, will be discussed. The Principle of Agency will be introduced in this section. Afterwards, I will turn to look at the purpose of cloning and suggest that if cloning is beneficial, it is permissible to act even if it may be unnatural. Next, I will stress some concerns about human cloning. They are personhood and uniqueness, genetic diversity and the misuse of cloning technology. Last but not least, animal cloning will be mentioned.
What is cloning?
In order to avoid confusion, it is essential to describe what I mean by cloning. Cloning may have different meaning in different context. Basically, "the asexual reproduction of plants, the budding of yeast in beer, the formation of identical twins and the multiplication of cells to repair damaged tissue in the normal process of healing" can be regarded as cloning. Also, "cloning techniques in plants have been in widespread use for centuries in gardening and crop development" (House of Representatives Standing Committee on Legal and Constitutional Affairs, 2001, p.18). However, they are not the concern of this essay. I rather focus on cloning through artificial technologies. House of Representatives Standing Committee on Legal and Constitutional Affairs state that DNA, cells, tissues, organs and even the whole individuals can be cloned. It is worthwhile to note, "cloning does not necessarily mean the replication of an entire individual" (2001, p.18).
There are two major cloning technologies: somatic cell nuclear transfer, and the isolation and characterization of human embryonic stem cells. To demonstrate somatic cell nuclear transfer, consider the Dolly experiment. Dolly the sheep was the first successful cloned mammal. In the experiment, a somatic adult cell was fused, by an electric pulse, with a nucleus-removed egg. The fused cells formed an embryo. The embryo is then transferred to the uterus of another sheep. Dolly the sheep was born after a normal pregnancy. She was the only sheep born after 277 attempts and the failures "resulted in abnormal placentas and fetuses and other complications during pregnancy or at birth" (2001, p.19-20). The second technique is embryonic cloning. An early pre-implantation embryo is taken. The embryo can be separated and each part will grow into genetically identical fetuses. Consequently, more embryos can be obtained for later use (Holland, 2003, p.192).
Natural VS unnatural
Some people hold the view that "it is ethically unacceptable to alter a species genetically." On the other hand, as Wilmut points out, we are using this technology widely (1998, internet). This is indeed the argument over nature. Some people maintain that artificial manipulation of genes is unacceptable, while the others do not. In this section, I will discuss this problem in general.
Holland presents the argument from nature and rejects it. Take homosexuality as an example. It is attacked as "unnatural" and Holland defends by saying "it's an expression of some people's natural (in the sense of being bestowed rather than chosen) sexual preference." Moreover, what is natural may not be good. Holland further questions that if the natural is defined as opposite of human artifice and manipulation, then isn't everything unnatural? For example, it is unnatural to put up an umbrella because we interfere the natural tendency of rain (2003, p.152-153). Holland's argument seems convincing. He gives examples on how is natural bad and how does human being acts unnaturally. But then, the opposite side may also give examples on how is natural good and how do we act naturally. What is natural is sometimes good and sometimes bad. Hence, the argument from nature should not be overthrown universally yet. It is crucial to look at particular situation.
Rachels proposes the Principle of Agency:
If it would be good for a particular state of affairs to occur "naturally", without being brought about by human action, then it is permissible to act to bring it about (1998, p.154).
This sounds plausible. According to Rachels, a challenge to this principle is that it is a consequentialist principle and consequentialism is controversial. So Rachels goes on to explore the problem. A central argument is about intentions. There are two views of intentions: the direct effect view and the indirect effect view. In the former view, the same act may be right when done with one intention; and may be wrong when done with another intention. In the latter view, "actions done with different intentions are different actions." So, the morality of the action depends on intentions. Rachels claims that if you found trouble with the direct view, you would simply replace "to act so" by "to act with intention" in the principle. He then moves on to talk about rights. He states that there is no conflict between the Principle of Agency and rights. It is unlikely that we violate anyone's rights by acting to bring about the good (1998, p.154-160).
The Principle of Agency is convincing. It is permissible to act if the intention is good. This is equivalent to good intention is a sufficient condition to act. Consider taking medicine as an example. If one is sick, one will probably take medicine. Taking medicine is unnatural because it attacks the nature that one is sick. But he takes medicine because he wants to overcome the sickness and this is good for his health. Thus, acting unnaturally should not be forbidden. We should ask what is the purpose of the action instead. This leads to the next question: what is the purpose of cloning?
What for?
By analyzing Stephen Holland and James Rachels' arguments, we have seen the discourse upon natural and unnatural. Applying to the case of cloning, whether or not artificial manipulation of genes is acceptable depends on the purpose. The crucial question is: why do we need cloning?
John Harris describes several potential applications. I will outline them as follows. First, cell nuclear replacement (CNR) can be applied to cell therapy. The key is that "embryonic stem cell (ESC) have the capacity to differentiate in all human tissues (except for extra-embryonic)," that is to say, any damaged or fault part of our bodies can be repaired or rebuilt with the help of ESC. Also, there won't be shortage of tissues and immunological rejection anymore. Second, compatible organs can be created. This solves the problem of shortage of organs. The third one is about the treatment of mitochondrial disease (2004, p.6-8). These applications are permissible, given that it significantly benefits human beings.
Harris gives the fourth application that an embryo can be cloned or created for the purposed of research (2004, p.9). This is often controversial. Should we consider an embryo as a human being? Or we may put it like this: does the early embryo have moral status? Some authors refuse creating embryos for research (for example, see Holland, 2003; Keenan, 2001, p.67). While the others find it permissible. For instance, Campbell premises uses of embryos as research resources, but ethical justification should be taken into account (2001, p.47).
It is worthwhile to discuss why using an early embryo in research is permissible. Peter Singer states that if we reject medical advances because they are unnatural, then we have to reject the modern medicine entirely (2001c, p.536). This is similar to the point I made in the last section. Singer then attempts to answer the question. When does an embryo acquire rights? He proposes that we cannot harm the embryo until it has the capacity to feel pain. The embryo has the potential to become a person. But before the embryo turns to a sentient being, it has not been harmed even if we damage it. Controls should be taken into consideration only when the embryo is capable of feeling. Singer argues that an embryo can be used for research before "it has formed a brain and a nervous system" (2001c, p.539-540).
Another challenge is that the embryo has potential to become a human, so it is morally significant. Harris opposes this view. He claims that an embryo does matters when it had undergone changes. The following example is given. All human beings are potentially dead, but we do not treat anyone as dead beings. Furthermore, the egg and the sperm have potential to become an embryo, and that an embryo has potential to become a human. If we had to regard everything, which has potential to become a human being, morally significant, then we would be exhausted. Even if we assume that only the fertilized egg has potential to become a human, it is not so morally important (1998, p.50-52). Overall, if medical advances are beneficial to human beings, it is permissible to create and use early embryos in research. As Harris states, embryo research improves in vitro fertilization. More importantly, it helps to save lives (1998, p.59-60).
So far, I have discussed the concern that cloning is unnatural and suggested that it may be resolved by considering the purpose of cloning. If it has positive benefit, it is permissible to act unnaturally.
Concerns and worries about human cloning
This section discusses several concerns and worries about cloning. They are personhood and uniqueness, genetic diversity and the misuse of cloning technology.
It is claimed that cloning may lead to loss of personhood. Does it really matter? Technically, the cloned person is genetically identical to the person being cloned. That is it. Like twins, cloning will not produce identical person (Gillon, 2001, p.190; Harris, 2004, p.45-46). What makes a person unique? Genes, consciousness, memory, mental features and the body may be taken into account. But the gene itself does not matter, given that the cloned person and the person being cloned are two individuals. Growing up in different environment probably makes different persons. How a person thinks depends on what he already knows. It can be shown that prior knowledge affects perception and learning greatly. Personhood is far from being affected by genetic identity even at the beginning stage. Therefore, the cloned person does not violate the rights of anyone, nor can he cause others to lose their personhood.
Genetic diversity is another concern. Evolutionary biology tells us that genetic diversity is good to protect human beings from diseases. It is argued that cloning limits this genetic progress. This critic assumes that cloning will be a mass production. This is unrealistic (Brock, 2001, p.112; Harris, 2004, p.50; Pence, 2004, p.82-83). There is a general worry that if human beings took control of something, the consequences would possibly be bad. Rachels illustrate this worry with the following examples. "If euthanasia is permitted, we will end up killing the inhabitants of retirement homes; or if cloning is permitted, there will be rooms of artificially-created people silently growing spare parts." People tend to feel that the only way to prevent bad consequence is prohibiting the whole action. Rachels comments that it is slippery slope and the worries are less fundamental issues (1998, p.154-156). Nonetheless, have we underestimated this problem? Imagine millions of Albert Einstein or Adolf Hitler are hanging around. To prevent this, something has to be done.
If technology improves human life, it should not be banned. Of course, cloning technology has both advantages and disadvantages. The point is, how do people use it? As Mary Warnock puts it, "control should not be over research, but over the uses of research" (2001, p.233). The concerns mentioned above focus on the misuse of cloning technology. After the birth of Dolly the sheep is announced in Nature, the public worries about human cloning. Warnock insists "to legislate in such circumstances, in response to popular feeling, is almost always a mistake." Meanwhile, scientists are not absolutely free to do whatever they want. Also, the parliament and general public are ignorant of scientific research. So scientists should report the facts and probabilities to the public. Then judgment is made. Although legislation may not be necessary, regulation should be imposed. Scientists, practicing doctors, lawyers, philosophers and level-headed persons form a committee of inquiry. They should also seek public opinions before making moral judgments. The most important is "anonymous departmental civil servants – even if, as one hopes, they are strictly impartial and not under pressure from their ministers - cannot take on the educative role that is necessary in such cases" (2001, p.234-236).
Animal cloning
In the last section I focused on human cloning. Now I turn to discuss animal cloning.
How should humans treat animals? First, as Peter Singer states, "the principle of the equality of human beings is not a description of an alleged actual equality among humans: it is a prescription of how we should treat human beings" (2001a, p.275). He also fights for animals. He suggests that moral principles should be extended to animals (2001a, 2001b). It sounds reasonable to treat human beings and animals fairly. But what if human rights and animals right conflict with each other? I urge that there is a priority. Human beings are more important than non-human animals. I am not allowing anyone to cut a mouse's leg off and make it run for the purpose of his enjoyment. The point is, when two rights conflict, decision has to be made.
Now return to the question that when is animal cloning permissible? Or generally, can researches on animals be justifiable? We may, as Peter Singer advises, treat the animal as a brain-damaged human being (2001a, p.279). The basis is, if certain experiment on humans is allowed and human rights are not violated, then the experiment on nonhumans is also allowed.
Conclusion
My claim in this essay is that cloning can be ethically permissible under certain circumstances and such technology needs not to be banned. The crucial point is that if cloning is beneficial to human being, it is permissible. Particularly, say, embryo researches are allowed because they help to advance medicine. Pain and suffering of any sentient being should be prevented.
Bibliography
Brock, D.W. (2001) Cloning Human Beings: An Assessment of the Ethical Issues Pro and Con. In Lauritzen, P. (ed.) Cloning and the Future of Human Embryo Research. New York: Oxford University Press.
Campbell, C.S. (2001) Source or Resource? Human Embryo Research as an Ethical Issue. In Lauritzen, P. (ed.) Cloning and the Future of Human Embryo Research. New York: Oxford University Press..
Gillon, R. (2001) Human Reproductive Cloning: A Look at the Arguments against It and a Rejection of Most of Them. In Klotzko, A.J. (ed.) The Cloning Sourcebook. New York: Oxford University Press.
Harris, J. (1998) Clones, Genes, and Immortality: Ethics and the Genetic Revolution. New York: Oxford University Press.
Harris, J. (2004) On Cloning. New York: Routledge.
Holland, S. (2003) Bioethics: A Philosophical Introduction. Cambridge, U.K.: Polity Press.
House of Representatives Standing Committee on Legal and Constitutional Affairs. (2001) Human cloning: scientific, ethical and regulatory aspects of human cloning and stem cell research. Canberra: The Parliament of the Commonwealth of Australia.
Keenan, J. (2001) Casuistry, Virtue, and the Slippery Slope: Major Problems with Producing Human Embryonic Life for Research Purposes. In Lauritzen, P. (ed.) Cloning and the Future of Human Embryo Research. New York: Oxford University Press.
Pence, G.E. (2004) Cloning after Dolly: Who's Still Afraid? Lanham: Rowman & Littlefield Publishers, Inc.
Rachels, J. (1998) The Principle of Agency. Bioethics, Vol.12, No.2. Oxford: Blackwell Publishing.
Singer, P. (2001a) All Animals are Equal. In Mappes, T.A. and DeGrazia, D. (ed.) Biomedical Ethics. (5th ed.) New York: McGraw-Hill.
Singer, P. (2001b) Cloning Humans and Cloning Animals. In Klotzko, A.J. (ed.) The Cloning Sourcebook. New York: Oxford University Press.
Singer, P. (2001c) Creating Embryos. In Mappes, T.A. and DeGrazia, D. (ed.) Biomedical Ethics. (5th ed.) New York: McGraw-Hill.
Warnock, M. (2001) The Regulation of Technology. In Klotzko, A.J. (ed.) The Cloning Sourcebook. New York: Oxford University Press.
Wilmut, I. (1998) The Uses and Ethics of Cloning. Encyclopædia Britannica Online. Retrieved April 9, 2006, from http://www.search.eb.com/eb/article-9114102
