One Monkey, Two Monkey

By: Alysa Rogers

In July 1996, researchers at the Roslin Institute made history with the birth of the now-famous sheep Dolly. What made Dolly famous was not that she was the first cloned animal (the Roslin Institute had cloned two animals previously). Instead, she became famous through the method in which she was created: she was created using an adult cell (the two cloned animals before her were cloned using embryonic cells). Before Dolly’s birth, scientists were convinced that this was the only method in which an animal could be cloned–embryonic cells have the potential to become any type of cell, whereas adult cells are specialized and set into their specific functions. With Dolly, the Roslin Institute created a new method with which they could clone an adult animal.

Researchers created Dolly using DNA from a mammary cell of a six-year-old Finn Dorset sheep and the egg cell of a Scottish Blackface sheep. In a process called somatic cell nuclear transfer, the nucleus of the mammary cell was extracted by scientists and placed in the egg cell, which had been previously de-nucleated. Several of these hybrid cells were then implanted into a foster mother, later resulting in Dolly’s birth.


Dolly the Sheep’s creation (TIME Magazine, March 10, 1997)

Since Dolly, scientists have continued pushing the bounds of cloned animals: since the announcement of Dolly’s success, researchers have cloned horses, cats, mice, dogs, and rats, many with innovative and ingenuitive new methods. One boundary stayed constant: primates weren’t successfully cloned. Concerns that cloning primates might lead to cloning humans held researchers back, as well as complications in cell division in attempts to clone rhesus macaque monkeys. Differences in primate eggs caused somatic cell nuclear transfer to simply not work, allowing cells to survive through only a few divisions before dying.

That is, until now. It was just announced that researchers in China successfully cloned two rhesus macaque monkeys, named Zhong Zhong and Hua Hua, using somatic cell nuclear transfer. Like Dolly, the two primates break bounds that scientists thought impossible. The researchers who created the monkeys proposed that cloning monkeys be used in biomedical research to decrease variability and, in theory, reduce the number of monkeys needed. This cloning is just a first step, though–the monkeys may encounter complications due to being cloned later in their lives, and researchers simply aren’t ready to begin cloning primates on a large scale.

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Hua Hua (Qiang Sun, Mu-Ming Poo; Chinese Academy of Sciences)

The possible positives that come from the breaking of this barrier are just one side of the coin. This discovery has finally made it possible for researchers to potentially clone a human: monkeys and humans aren’t, after all, so different from a biological standpoint. Zhong Zhong and Hua Hua may end up overshadowing Dolly in importance simply because of the ethical dilemmas raised in conjunction with their cloning. Is it ethical to clone animals? Is it ethical to clone humans, whether for research or otherwise? Are we drawing nearer to the previously foreseen “designer babies”? And, what does this mean for our future?



Beardsley, Tim. “Cloning Hits the Big Time.” Scientific American, Scientific American, 2 Sept. 1997,

“The Cloning of Dolly and Other Mammals.” Biotechnology: Topics in Biotechnology, Indiana University – Purdue University Indianapolis, 27 Oct. 2009,

Greshko, Michael. “Monkey Clones Created in the Lab. Now What?” National Geographic, National Geographic Society, 24 Jan. 2018,

“The Life of Dolly.” Dolly the Sheep, The Roslin Institute,

Vogel, Gretchen. “The Problem With Cloning Primates.” Science Magazine, Science Magazine, 10 Apr. 2003,


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