Although the possibility of
cloning humans had been the subject of speculation for much of the 20th century, scientists and policymakers began to take the prospect seriously in 1969.
J. B. S. Haldane was the first to introduce the idea of human cloning, for which he used the terms "clone" and "cloning", which had been used in agriculture since the early 20th century. In his speech on "Biological Possibilities for the Human Species of the Next Ten Thousand Years" at the
Ciba Foundation Symposium on Man and his Future in 1963, he said: Nobel Prize-winning geneticist
Joshua Lederberg advocated cloning and
genetic engineering in an article in
The American Naturalist in 1966 and again, the following year, in
The Washington Post. He sparked a debate with conservative bioethicist
Leon Kass, who wrote at the time that "the programmed reproduction of man will, in fact, dehumanize him." Another
Nobel Laureate,
James D. Watson, publicized the potential and the perils of cloning in his
Atlantic Monthly essay, "Moving Toward the Clonal Man", in 1971. With the cloning of a sheep known as
Dolly in 1996 by
somatic cell nuclear transfer (SCNT), the idea of human cloning became a hot debate topic. Many nations outlawed it, while a few scientists promised to make a clone within the next few years. The first
hybrid human clone was created in November 1998, by
Advanced Cell Technology. It was created using SCNT; a nucleus was taken from a man's leg cell and inserted into a cow's egg from which the nucleus had been removed, and the hybrid cell was cultured and developed into an
embryo. The embryo was destroyed after 12 days. In 2004 and 2005,
Hwang Woo-suk, a professor at
Seoul National University, published two separate articles in the journal
Science claiming to have successfully harvested pluripotent,
embryonic stem cells from a cloned human blastocyst using SCNT techniques. Hwang claimed to have created eleven different patient-specific stem cell lines. This would have been the first major breakthrough in human cloning. However, in 2006
Science retracted both of his articles on account of clear evidence that much of his data from the experiments was fabricated. In January 2008, Dr. Andrew French and
Samuel Wood of the biotechnology company
Stemagen announced that they successfully created the first five mature human embryos using SCNT. In this case, each embryo was created by taking a nucleus from a skin cell (donated by Wood and a colleague) and inserting it into a human egg from which the nucleus had been removed. The embryos were developed only to the
blastocyst stage, at which point they were studied in processes that destroyed them. Members of the lab said that their next set of experiments would aim to generate embryonic stem cell lines; these are the "holy grail" that would be useful for therapeutic or reproductive cloning. In 2011, scientists at the New York Stem Cell Foundation announced that they had succeeded in generating embryonic stem cell lines, but their process involved leaving the
oocyte's nucleus in place, resulting in
triploid cells, which would not be useful for cloning. In 2013, a group of scientists led by
Shoukhrat Mitalipov published the first report of embryonic stem cells created using SCNT. In this experiment, the researchers developed a protocol for using SCNT in human cells, which differs slightly from the one used in other organisms. Four embryonic stem cell lines from human fetal somatic cells were derived from those blastocysts. All four lines were derived using oocytes from the same donor, ensuring that all
mitochondrial DNA inherited was identical. A year later, a team led by
Robert Lanza at Advanced Cell Technology reported that they had replicated Mitalipov's results and further demonstrated the effectiveness by cloning adult cells using SCNT. In 2018, the first successful
cloning of
primates using SCNT was reported with the birth of two live female clones,
crab-eating macaques named
Zhong Zhong and Hua Hua, and there have been several similar reports since. However, all these cases involved cloning of fetal cells - as yet, no primate has been cloned from adult cells. ==Methods==