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Is an animal-human hybrid an ethical monstrosity – or a scientific breakthrough?

2008 March 28
by Paul Vallely



New departures in bio-ethics, including saviour siblings, embryo selection and fatherless children

Catholics in the Cabinet, we keep being told, are “wrestling with their consciences” on the question of human-animal DNA fusions. Interestingly we have yet to hear from these ministers themselves. That may be tactical. Or it may indicate that the subject is more complicated than billed.

Catholic prelates have had a deal to say on the need for politicians to have “an informed conscience”. But that cannot mean for a Labour MP who is a Catholic that the Labour whip must be replaced by a Catholic whip. To act in good conscience they need to inform themselves on the detail of the science as well as on the teaching of the church.

The problem I have, as a Catholic, is that the science suggests something other than a  “monstrous attack on human rights, human dignity and human life”, to quote Cardinal Keith O’Brien, who also threw in words like grotesque, hideous and Frankenstein.  But we need more than the “yuk” factor to guide us here.

There are various kinds of possible animal-human hybrids. There are chimeras which could be formed by merging human and animal embryos. There could be hybrids made by fertilising a human egg with an animal sperm, or vice versa. And there could be cybrids made by inserting human DNA into an animal egg from which the nucleus has been removed.

The first two, which would justify the Scottish cardinal’s extravagant language, are not what is being considered in the bill before Parliament. It concerns only the third, which would take a human skin cell and placing it inside a cow’s egg from which the genetic material has been removed. The result would be grown in a laboratory for a few days, allowing the human DNA to revert to a state in which it is capable of issuing instructions for building every cell in the human body. The resulting stem cells would then be harvested to be used by scientists to discover how, when and why those instructions are switched on – and how they might be used to persuade the body to repair or replace its defective cells.

The idea that this violates a deep taboo or destroys the concept of human uniqueness or redefines what it is to be a human being is predicated on the assumption that what is being created is an embryo. This is why we hear talk about “unborn human life” or even “experiments on babies”. And yet using animal eggs to re-programme adult skin cells in a cell-cluster without a nervous system is not creating an embryo in any meaningful sense. This is not the product of a sperm and egg. It could not survive much more than a week in vitro. The proposed law would make it illegal to sustain it for more than 14 days or to implant it in a human or animal womb.  Nothing which is recognisably human life is being created or terminated. Indeed the creation of this cell cluster will reduce scientists demand for research on genuine human embryos.

The Church has traditionally recognised limits to the argument that we must not do things that are not natural. There were no ethical objections when faulty human heart valves were replaced with ones taken from pigs or when genes were added to farm animals to make them produce human insulin. Fusions of human and animal cells have been used as research tools since the 1960s; they helped map the human genome, identified genes that cause human cancers and produced medical treatments such as monoclonal antibodies. The history of science, from animal breeding to chemical pharmacology to blood transfusions, is full of breakthroughs which once felt taboo-breaking.

Humankind is still at work in the creation process as divine agents. To recognise that is not to deny that there is something distinctive and valuable about human beings. It is rather to acknowledge and to celebrate the gifts they have been given.


Why do we have children? To fulfil a biological need. To make a relationship complete. To carry on the family name. To provide a playmate for an existing child. To bring a daughter into a family full of boys. To bind together a shaky marriage. To find someone to love. To ensure we have someone to look after us in our old age. To provide more hands on the farm or a successor for the family firm. To move up the waiting list to get a council flat. To increase our income from state benefits. Because we forgot the contraception.

Most people could add considerably to that list, for the answer is both multifaceted and varying. We might add one more – the idea that another one reason for having a child is so that their umbilical cord, of blood or bone marrow can be used to save the life of an existing child who has a life-threatening illness?

The proposal to enshrine the principle of such “saviour siblings” in British law is another of the controversial elements of the Human Fertilisation and Embryology Bill which MPs will be voting on in coming weeks. Unease centres on three areas.

Philosophically it involves looking at the saviour sibling as a mere instrument or means to and end rather than as a child created for its own sake. Physically or psychologically the business of donation might harm the second child. Theologically it raises, again, the question of when human life begins, since it can only be done by creating a number of embryos and discarding those that are not suitable – either because they are found to have the same family gene which caused the elder sibling’s disease or because they turn out not to have the gene which would make them match as a potential donor.

The philosophical objection seems flawed because there are so many overlapping reasons in nature, some admirable, some distinctly dodgy, for having a child. Few babies are conceived only for a single one of the reasons in our opening list. The argument that saviour siblings treat the offspring to be born as a commodity would only hold if the child were merely treated as a tissue farm and then killed or given away once it had served its therapeutic purpose for its elder brother or sister.

If a child is to be loved this is no more instrumental than attempting to conceive a child as a playmate for an existing child, which is seen as reasonable. What applies here is a similar dual purpose argument as Thomas Aquinas outlined in his principle of double effect, which offers moral justification for killing someone in self-defence or as an unavoidable side-effect of drugs given to manage unbearable terminal pain. It is an complementarity which the Church recognises in other areas, such as in acknowledging that sex is not simply about procreation but also about loving bonding of a married couple.

Concerns about physical or psychological harm to the new child are very proper. But these do not require an outright ban but merely pragmatic regulation. The rule the authorities have already established seem perfectly adequate. Embryo selection can only be done where there is a risk that the second child could carry the same hereditary disease, so the process involves the good of the second child as well as the first. It can only be done where a sibling is the beneficiary, not a parent. Embryos cannot be genetically modified to provide a tissue match. Monitoring of the continuing wellbeing of the saviour is required.  No treatment can be pursued which would seriously harm the saviour.

So the only substantial argument against saviour siblings is the argument that all embryo selection to avoid hereditary diseases is wrong. I shall look at that next week.


Should a couple risk having a child if they know one of them carries a gene which could give the baby a life-threatening condition like cystic fibrosis? Or should they be allowed to screen their embryos so that only a healthy one is implanted in the mother’s womb? Welcome to another of the moral dilemmas woven in to the Human Fertilisation and Embryology Bill currently before parliament. It is perhaps the central conundrum.

Such screening, known as preimplantation genetic diagnosis (PGD), can only be used to test for single-gene defects like cystic fibrosis. If a family knows that they are at risk they may opt to use embryo selection which involves taking several eggs from the mother fertilizing them in a test tube, and then letting the fertilized eggs divide to the 8 or 16-cell stage. At this point a single cell is removed and tested; embryos with the defect are discarded; those which are defectless are implanted.

The crucial moral dilemma turns on whether the fertilised embryo can be defined as a human person. This is where the embryo selection debate diverges from the abortion one.

Conservative moral theology insists that a human person exists from the moment of conception, which is commonly taken to be synonymous with the fertilisation of the egg by the sperm. But there is another key factor in conception and that is implantation; until the fertilised egg is implanted in the womb the fact of fertilisation is insufficient. This is more than saying that the value of any human life depends on its place of residence, uterus or petri dish; it is to include the necessary consideration of viability.  Some 70 per cent of fertilised embryos are thought not to implant in nature; fertilised embryos do not seem to be paramount in the eyes of God.

This is where the space opens between the abortion and the embryology debates. If implantation is a decisive factor then it does not necessarily follow that the creation of a fertilised egg in vitro is wrong; and even if the fertilised egg is worthy of respect it does not follow that it is more worthy of respect than a child or adult with a life-threatening disease.

A dilemma, after all, is a choice between two undesirable alternatives. The destruction of discarded embryos may be a lesser evil than failing to prevent the death of a child or adult. Unimplanted embryos are clearly human life, but if they are not fully human persons then PGD may be permissible in certain circumstances. (Legislators should ensure that embryo selection is not permissible for minor disabilities, like cleft palates). For though killing a human individual can never be a therapeutic intervention the gathering of stem cells from an unimplanted embryo might be.

The Vatican’s argument against IVF and embryo selection – and indeed saviour siblings, where a child is born whose umbilical blood can save the life of its sister – is that good can never be achieved through the discarding of human beings; even if embryos have defects they are still persons and killing them is as wrong as killing disabled people would be. But if implantation is regarded as a necessary condition, transforming the fertilized egg into the viable embryo, then the argument changes considerably.

There are two alternatives to embryo selection. One is the perfectly legal, but morally much more questionable, option of a late abortion once the foetus has been tested and shown to carry the life-threatening disease. The other is to condemn such couples to a genetic Russian roulette. Embryo selection seems far less objectionable.  It is important in all this that the Church should not confuse the principles of moral theology with the interpretation of scientific fact.


Does a child need a father? At present the law requires that fertility clinics take account of the “need for a father” when deciding on whether a woman is suitable for IVF treatment. That is about to change. The draft Human Fertilisation and Embryology Bill wants to replace the need for a father with a requirement for “supportive parenting”.

In contemporary culture this is perhaps the least controversial part of the bill. The Christian and political right point to the social indicators which show that children are healthier, happier, and do best when they live in stable families where their mother and father are married. The evidence seems clear on this. But should we make the best the enemy of the good? Experience also shows that there are same-sex couples who make excellent parents.

Sexual politics rears its head here. Some clinics have a blanket ban on same-sex couples. Others routinely accept lesbians but not gay men. But things are changing. In Spain, Canada and the United States a birth certificate no longer says Mother and Father but Parent A and Parent B. The prevailing social norm is that it all really doesn’t matter so long as the child is loved.  The question is seen to turn around the equal right of any adult to have a child. But adults’ deep emotional and biological urge to have a child cannot overwhelm the right of a child to have a father.

The IVF debate diverges from the gay adoption debate here. Even some who see heterosexual marriage as the ideal concede that for a child in care living with lesbian parents is infinitely preferable to being in a children’s home. Indeed some children may, early in life, have been so damaged by their experiences with one gender, that they may be better placed with a couple of the opposite gender.

But these arguments do not have the same purchase in the case of IVF where the potential child has a right to the best available, to know both her parents, and to make sense of his identity in the light of both male and female role models. This goes well beyond health arguments, about a child being able to trace their genetic identity in case of inherited illnesses.

It is only now that the first reports are emerging of the coming to adulthood of the first generation of children conceived by married heterosexual couples using sperm donors. They can now be found on the internet, talking about their search for identity, their yen to know their biological fathers or their quest for half-siblings. They have dubbed themselves “lopsided” or “half adopted.” A law passed in Australia in 1984 will this year, for the first time, mean that young adults may receive a letter from their biological father wishing to contact them.

The evidence on all this is far from clear-cut. Paediatric research has shown that children of lesbian or gay parents have similar upbringing experiences to children in heterosexual families. There is no difference in levels of child mental health problems such as anxiety, depression, behavioural problems, ADHD or autism. And common prejudices – that children of gay fathers will become gay themselves, or be molested by their fathers – have been countered by detailed research. Most child sex abusers are heterosexual men.

There are some differences: gay fathers were found to be more consistent about setting and enforcing limits on their children’s behaviour; lesbian mums were found to have more imaginative play than single heterosexual mothers; smacking was less common. On the other hand some children of lesbian couples had lower self-esteem where they perceived stigma attached to the family. And 20 per cent of children of gay men had experienced discrimination.

More long-term studies are clearly required. But a massive social experiment is underway and legislators should proceed with care.

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