China Daily via Reuters

They Cloned Monkeys. Are Humans Next?

Researchers in China recently cloned two monkeys, the first primates to be created with the technique that produced Dolly the sheep more than 20 years ago (see “Cloning Milestones,” facing page). The long-tailed macaques, named Zhong Zhong and Hua Hua, were made from fetal cells grown in a petri dish. Born in Shanghai, they’re identical twins and carry the exact DNA of the monkey fetus that provided the cells. This accomplishment brings scientists closer to being able to clone humans, a controversial idea long in the realm of science fiction. Although cloning animals has helped researchers develop new medical treatments, some question whether duplicating a human would be ethical, given the risks that something could go wrong. (Another Chinese scientist made people nervous in November when he claimed that he had altered a gene in the embryos of a pair of human twins, making them resistant to H.I.V. infection—although he offered no proof at the time.) One thing is certain: The speed of advances in genetics means that we will all need to ponder the implications soon. “We are closer to [cloning] humans than we’ve ever been before,” says Dr. Leonard Zon, director of the stem cell program at Boston Children’s Hospital. “That raises questions of where we would want to go.”

Cloning Milestones

The Asahi Shimbun via Getty Images

1952: The first successful cloning attempt: Using a frog embryo and egg, scientists are able to create a new tadpole.

1996: Dolly the sheep is the first mammal cloned from adult cells. This method had been thought impossible before.

2005: An Afghan hound clone, Snuppy, is born. It’s a breakthrough, as dogs had proved tricky to clone.

2013: Cloned human stem cells are made. Experts hope one day to use cloned stem cells to create human organs for transplanting.