1952- First cloning experiment: unsuccessful

1970-Successful cloning of a frog

1980- Human cloning suggested in a novel

1981- First mammal, a mouse, is cloned

1984- First embryo cloning with a lamb

1994- First cloning of more advanced embryos of a lamb

1996- Research begun on clonig an adult sheep

1997- The first adult mammals (sheep) are cloned. Clinton issues moratorium on human cloning