Every year sees lots of new technology, new drugs, and new techniques. Much more rarely does a whole new field open up, with the prospect of transforming whole economies and societies. This year, however, we may have seen two such breakthroughs.

One is the advent of practical cloning and genetic modification of animals, with all that that implies for reshaping and replicating animals - and humans too, if we wish to go that way.

In February 1997, scientists at the Roslin Institute in Scotland revealed the existence of "Dolly", a sheep grown from a cell taken from her mother's udder. They all swore blind that they would never clone a human being, of course - but they did say that it would be technically possible within two years. In July, Dr Ron James of PPL Therapeutics, the Scottish firm that funded the Roslin research, announced that their next goal was to breed sheep and cows with human DNA who would "manufacture" key components of human blood in their bodies.

"We know from our work with Dolly that we can create genetically engineered animals from a single cell," he said. "Now we want to use that technology to produce one of the fundamental constituents of the human body."

In the same month, at Juntendo University in Japan, a team led by Dr Yoshinori Kuwabara released pictures of an "artificial womb" in which they have been bringing premature goat foetuses to term. The embryos were removed from their mothers at 17 weeks and spent the rest of their gestation period in an open-topped acrylic tank filled with liquid at blood temperature that simulated amniotic fluid. The placenta was replaced by a machine that pumped oxygen and nutrients into the embryo's blood. "This system should be used on behalf of the mother who cannot keep the foetus in her uterus," said Kuwabara. If I have time and money for experiments, maybe within 10 years we will have made the move from animals to humans."

But observers noted that the same technique might be used to grow clones from human tissue for use as "organ banks", without any need for messy wombs and meddlesome mothers. Growing complete human beings, even clones, and then "harvesting" organs from them would be illegal anywhere on earth. (It's called murder.)

But in October, Dr Jonathan Slack of Bath University in England announced that he can create headless frog embryos by manipulating certain genes. The same technique could easily be applied to human beings, he observed - which might solve the ethical dilemma of growing humans as "organ banks".

"It occurred to me that a half-way house could be reached," Slack added. Instead of growing an intact (human) embryo, you could genetically reprogramme the embryo to suppress growth in all the parts of the body except the bits you want, plus a heart and blood circulation."

So, when your vital organs start to fail, the doctors may just clone a "partial embryo from one of your cells, grow it in a Kuwabara tank, and harvest healthy, rejection-proof new organs from it. Some people will call it murder, and some won't - and that's going to be one of the major fault lines of 21st-century politics.

- Gwynne Dyer