The first monkeys to be created from the embryos of several individual monkeys were born at the Oregon National Primate Research Center at Oregon Health & Science University, a study published in the journal Cell reported.
The researchers say they essentially glued cells from separate rhesus monkey embryos together and successfully implanted the mixed embryos into mothers to create normal healthy monkey infants.
The key, they said, was using cells from very early stage embryos, when each individual embryonic cell is what is known as totipotent -- capable of giving rise to a whole animal as well as the placenta and other life-sustaining tissues.
This is in contrast to pluripotent stem cells, which can differentiate into any tissue type in the body, but not into extra-embryonic tissues or entire organisms.
"The [totipotent] cells never fuse, but they stay together and work together to form tissues and organs," researcher Shoukhrat Mitalipov said. "The possibilities for science are enormous."
Chimeric animals, especially mice, have become a powerful research tool, giving insights into processes of embryonic development -- such as why a particular cell gives rise to a specific kind of tissue and how individual genes work.