Leading article: The argument for hybrids

Yesterday's announcement by the Human Fertilisation and Embryology Authority that it would allow "in principle" the creation and cloning of animal-human embryos is to be welcomed. This long-awaited decision is not the final green light for scientists – that will come perhaps in November when the first licence applications are expected to be approved – but it marks a milestone in the long ethical and legal debate over such research.

The insertion of human chromosomes into an empty animal's egg cell can result in a new class of embryonic stem cell. These "progenitor" cells promise to help scientists to develop a range of new techniques for the understanding and eventual treatment of diseases such as Parkinson's and motor neurone disease.

As the Authority made clear in its statement, the creation of embryos that are genetically 99 per cent human but less than 1 per cent cow or sheep presents completely novel legal, scientific and ethical issues. In 1990, when the existing law on embryo research came into force, the possibility of creating a part-animal, part-human embryo was simply not contemplated. Some lawyers thus questioned whether these "hybrid" embryos were covered by the Act.

When the HFEA decided earlier this year to delay a decision on two licence applications until it had undertaken a full public consultation, the scientific community launched a major public-relations assault. Quite rightly, it wanted to make sure the public knew exactly what was at stake if British scientists were denied the opportunity of creating such embryos – which is the case in some other countries.

This appears to be the crux of the debate. Those who do not already hold major ethical or religious objections to research on human embryonic stem cells can, it seems, be persuaded of the justification for such work when the science – and its benefits – are explained.

For most of us, there are aspects of medical science that generate an instinctive "yuck" factor. The creation of an animal-human hybrid embryo sounds bizarre, if not deviant. However, when the facts surrounding the issue are made clear – that there is a shortage of human eggs to work with and that the resulting embryo will never be allowed to develop beyond 14 days – people can be made to understand the rationale.

For this reason, it is important for scientists to realise that they must never leave the public behind. The knowledge gap between the lay public and the experts may be widening, but it is up to scientists to make sure they keep us all fully informed about what they are doing, and – no less important – why.