BOB ABERNETHY: At a little-noticed meeting in Chicago about a month ago, a scientist dropped a bombshell. But it wasn't until this week that word of the startling announcement began to get out, sending shock waves through the scientific, religious, and ethical communities. The scientist, who has the felicitous last name of Seed, announced plans to clone a human being. Once a faraway fantasy of science, cloning -- the experimental replication of animals -- became fact last year, when scientists in Scotland cloned a sheep, quite successfully, apparently. There's word now that Dolly the sheep has been mated the "old-fashioned way," it is said.

After the successful animal cloning, the question becomes, will humans be next? Should humans be next? The debate over that has been fierce, and we have more on cloning and the questions it raises, beginning with this report from our contributing correspondent, Herbert Kaplow.

HERBERT KAPLOW: It was a sheep named Dolly who appeared on the scene about a year ago and astonished the world. She was, after all, one of a kind, or maybe better said, two of a kind. It happened in a laboratory in Scotland. Genetic material from one sheep was implanted in another. The result: Dolly, a genetic replica of the first sheep. About the first thing the astonished world asked was, "If it can be done with a sheep, could it or should it be done with humans?" The leader of the Scottish scientists said his team wasn't going to try it, but then American physicist G. Richard Seed appeared saying he will, and he talked with ABC's Ted Koppel about the religious implications.