Steve Connor: 'Scientists will be working on material with no potential to become a human being'

In nature, many animals exercise parthenogenesis for reasons such as the rapid generation of females when times are hard and food is too scarce to have it exploited by rival males.

The Roslin Institute has no intention of producing female babies by parthenogenetically activating human eggs. Its scientists merely want to understand the process of how a human egg matures and try to generate embryonic stem cells for medical purposes.

Since the birth of the first "test-tube" baby in 1978, a key finding of human reproductive biology has been the realisation that human eggs, sperm and embryos appear to be malleable outside the body.

It is possible to freeze them for years without any apparent damage, to inject otherwise defective sperm cells into unfertilised eggs and even to remove cells from early embryos without any ill effects.

Scientists are also discovering new ways of generating sperm, eggs and embryos from non-reproductive tissues, such as skin cells, and (in the case of embryos) from unfertilised egg cells.

A great advantage of creating an "embryo" from parthenogenetic activation of an unfertilised egg is that it would have no potential to develop.

This would mean they were in effect working on material with no potential to become a human being, which could circumvent the ethical and moral issues associated with research on human embryos created by the act of fertilisation.

Although it would be worthwhile to see if human stem cells could be derived from parthenogenic embryos, it is almost a byproduct of the research by the scientists, whose goal is to study ways of maturing human eggs from immature ovary tissue.

This is because to carry out Dolly-type cloning the scientists will need a far greater number of eggs than they currently have access to.

However, generating human embryos by the Dolly technique is a form of cloning. There should be no attempt to hide this.