Briefing on Hybrids

This issue is becoming important, so here is some more detailed background information. For the report on the Government's decision to legalise hybrids, see here. Don't forget to take part in the HFEA consultation, here.

What are hybrids? Also called 'chimera', human-animal hybrids are creatures with both human and non-human components.

Used broadly, the term includes a human with a animal organ transplant (such a pig's heart-valve), or an animal (such as a laboratory mouse) which has been injected with human brain cells. These cases can be medically and experimentally useful, and are not morally problematic. What is usually referred to, however, is the creation of an embryo with both human and animal genetic material. For this distinction see the 'Mary Meets Dolly' post here. In the latter case, if the creature were to reproduce, the genetic mixture would be passed on; in the former, it would not (it is not 'proliferative').

Hybrid embryos can be produced in three ways.
(1) A sperm of one species could be used to fertilise an egg of another, as happens when a horse and a donkey produce a mule; this might prove to be possible between humans and closely related species, such as chimpanzees, but has never been done.

(2) A human somatic cell nucleus (i.e. a nucleus from an ordinary cell, not a sperm or egg), can be inserted into an egg of another animal (such as a cow), from which the nucleus has been removed. Giving the product an electric shock can get it to start growing like a newly fertilised egg. All the genetic material would be human, with the exception of the mitochondrial DNA, which is outside the nucleus. This is called a cytoplasmic hybrid embryo. It has been claimed that this has been done.

(3) Genes of one species could be inserted into the DNA of another, at a very early stage of development; this would create a 'transgenic embryo'. So far, human genes have been inserted into animal embryos, but not vice versa. On all this see the HFEA consultation pdf here.

Why do scientists want to produce hybrids? For several reasons.

The shortage of human eggs means that making human embryos for experimentation - whether cloned or fertilised in vitro - difficult. Using human sperm or somatic cells and animal eggs would solve the problem. Also, it is hoped that there would be fewer ethical concerns about experimenting on a creature which is not fully human.

Another motive, bizarrely, is to annoy Christians by showing that humans are nothing but animals. How this would work as an argument is hard to see, but the proposal is reported here.

Finally, anything which hasn't been done before, and which is controversial, excites some members of the scientific community.

What are the medical or scientific benefits of hybrids? As with human cloning and embryonic stem cells, the claims made on behalf of hybrids are enormous, but the reality is different. A great many scientists have pointed out that hybrids tend to die very quickly, and have very little potential for medicine or research. On this, see Comment on Reproductive Ethics press release.

How much opposition is there to hybrids? It has been banned in a number of countries, including Canada, Australia, France and Germany, and condemned by a number of scientific bodies. See here for the Scottish Council on Bioethics; the Royal Society has said "There is at present insufficient scientific justification for creating human-animal hybrid embryos.''

What exactly is the ethical problem with hybrid embryos? Deliberately creating a creature with human and animal genetic material is an attack on the sanctity of human life.

It is true that the exact moral (and theological) status of a hybrid embryo is unclear, and may never be clear. It will also, no doubt, depend on the exact process used to produce the embryo. It may never be known, for example, if the products of a particular procedure would, when sufficiently developed, be rational: they may, after all, never survive very long. However, even humans with very severe handicaps have the right to be treated with respect, including the right to life, and hybrids could be thought of as severely, and deliberately, handicapped humans.

What is clear is that the deliberate creation of embryos whose humanity is unclear is itself a crime against human life: it is incompatible with respect for human life. No responsible parent would conceive a child with the intention that the child be handicapped, out of curiosity; that is effectively what the scientists are proposing to do. To subject hybrid embryos to destructive research, as is usually planned, on the plea that the moral status of the embryo is ambiguous, is another wrong: actions which may be murder should not be done.

Further information: 'Mary Meets Dolly'; 'Comment on Reproductive Ethics'; 'HFEA'