Cloning techniques could in the future allow a "Noah's Ark" of cells to save animals from extinction, British scientist Professor Sir Ian Wilmut predicts.
The idea would be to create an animal biobank in much the same way that seeds of rare plant species are currently preserved for posterity.
Sir Ian led the team that produced Dolly the sheep, the first mammal cloned from an adult cell, at the University of Edinburgh's Roslin Institute on July 5, 1996.
Part of the cloning process involved reprogramming adult cells to turn back their developmental clock.
Stem cell scientists later adopted the same technique to create induced pluripotent stem (iPS) cells from ordinary adult cells, such as those in the skin.
Like embryonic stem cells, iPS cells have the potential to become any kind of tissue in the body.
Speaking on the eve of Dolly's anniversary, Sir Ian said researchers had already made progress towards creating "gametes" - eggs and sperm - from iPS cells.
"We are looking some distance into the future but people are beginning to develop abilities to produce gametes from iPS cells," said Sir Ian.
"I would presume that one day with the species which are really studied we will be able to produce gametes, and therefore embryos."
This would "revolutionise" the business of conserving endangered species, he said.
Available cells of any kind could theoretically be stored in the biobank "ark" if the technology existed to transform them into reproductive cells.
The artificially created gametes could in turn be used to produce embryos from which species could be resurrected.
Success would depend on finding a suitable surrogate mother, said Sir Ian.
This would have to be a closely related species.
