The first embryonic stem cells were isolated in mice in 1981. But it wasn’t until 1998 that researchers managed to derive stem cells from human embryos. That kicked into full gear an ethical debate that continues to this day. Here’s a look at key moments in the controversy so far:
November 1995: Researchers at the University of Wisconsin isolate the first embryonic stem cells in primates — rhesus macaque monkeys. The research shows it’s possible to derive embryonic stem cells from primates, including humans.
January 1998: Scientist and entrepreneur Richard Seed announces plans to open a human-cloning clinic. The clinic would offer infertile couples the option of cloning themselves if there were no accepted medical treatments that could help them have a baby. Seed’s plan never comes to fruition, but the announcement spurs a debate on the ethics of human cloning.
Nov. 5, 1998: Researchers at the University of Wisconsin and Johns Hopkins University report isolating human embryonic stem cells. The cells have the potential to become any type of cell in the body and might one day be used to replace damaged or cancerous cells. But the process is controversial: One team derived their stem cells from the tissue of aborted fetuses; the other from embryos created in the laboratory for couples seeking to get pregnant by in vitro fertilization.
Aug. 23, 2000: The National Institutes of Health issue guidelines that allow federal funding of embryonic stem-cell research. Former President Bill Clinton supports the guidelines.
February 2001: The month after taking office, President George W. Bush requests a review of the NIH funding guidelines and puts a hold on federal funds for stem-cell research.
July 18, 2001: Sen. Bill Frist (R-TN) and Sen. Orrin Hatch (R-UT), a vocal abortion opponent, call for limited federal funding for stem-cell research.
July 29, 2001: House Speaker Dennis Hastert (R-IL) and other Republican House leaders come out in opposition to federal funding for research.
Aug. 9, 2001: President Bush announces his decision to limit funding to a few dozen lines of embryonic stem cells in existence at that date. Many of the approved lines later prove to be contaminated, and some contain genetic mutations, making them unsuitable for research.
Nov. 25, 2001: Scientists at Advanced Cell Technology in Massachusetts claim to have cloned a human embryo. However, the evidence proves controversial and not conclusive.
Feb. 12, 2004: South Korean scientists announce the world’s first successfully cloned human embryo. Unlike other past cloning claims, the scientists report their work in a prestigious, peer-reviewed journal, Science. The embryos were cloned not for reproductive purposes but as a source of stem cells. The news reopens the contentious debate over somatic-cell nuclear transfer, which is sometimes referred to as therapeutic cloning. Scientists say cloning offers a unique way to produce cells that may someday be used to treat diseases. But critics argue that any form of cloning is morally repugnant and should be banned.
June 25, 2004: New Jersey legislators pass a state budget that includes $9.5 million for a newly chartered Stem Cell Institute of New Jersey. The move makes New Jersey the first state to fund research on stem cells, including those derived from human embryos.
Nov. 2, 2004: California voters approve Proposition 71, which authorizes the state to spend $3 billion on embryonic stem-cell research over 10 years. The measure is a response to federal funding restrictions put into place in 2001. It puts California ahead of the federal government and many other nations in promoting the research.
May 19, 2005: The same South Korean researchers who reported cloning a human embryo in 2004 announce another milestone: They say they’ve created a streamlined process that uses far fewer human eggs to produce usable embryonic stem cells — a major step toward mass production. Their work is published in Science.
May 24, 2005: The House passes a bill that would ease President Bush’s restrictions on federal funding for stem-cell research.
May 26, 2005: A version of the bill passed in the House is introduced in the Senate. Among Senate sponsors of the bill are two prominent Republicans, Sen. Arlen Specter of Pennsylvania and Sen. Orrin Hatch of Utah. Their support comes despite President Bush’s promise to veto any legislation lifting the restrictions on funding he put in place on Aug. 9, 2001.
May 31, 2005: Connecticut approves $100 million in funding for adult and embryonic stem-cell research over the next 10 years.
July 13, 2005: Bypassing the Illinois state legislature, Democratic Gov. Rod Blagojevich creates a stem-cell research institute by executive order. The institute will be funded through a line item in the state budget that gives the Public Health Department $10 million to fund research.
July 29, 2005: In defiance of President Bush, Senate Majority Leader Bill Frist (R-TN) announces his support of legislation to ease federal funding restrictions for stem-cell research.
Sept. 19, 2005: Scientists in California report that injecting human neural stem cells appeared to repair spinal cords in mice. The therapy helped partially paralyzed mice walk again.
Sept. 21, 2005: Advocates of embryonic stem-cell research in Florida propose a ballot initiative that would give $200 million in state funds toward the research over the next decade. Two days later, opponents of the science file a petition to amend Florida’s state constitution to ban state funding for embryonic stem-cell research.
Nov. 11, 2005: University of Pittsburgh researcher Gerald Schatten alerts editors at the journal Science that there may have been ethical lapses in a landmark cloning paper published in February 2004. In that paper, South Korean scientists claimed they had made an embryonic stem-cell line from a cloned human embryo. Schatten alleged that some of the egg donors in that study had been paid, and some were junior colleagues of the lead author, Hwang Woo Suk. Schatten also says there were minor technical errors in one of the tables in a 2005 paper by the same group, a paper on which Schatten was senior author. In that paper, Hwang et. al. claimed to have made 11 cloned stem-cell lines. At the same time, Schatten severs his collaboration with the South Korean scientists.
Dec. 15, 2005: Hwang admits that there are serious errors in his 2005 paper in Science and asks the journal to retract it. The admission comes three weeks after Hwang apologized for ethical lapses and stepped down as head of the stem-cell program at Seoul National University.
Dec. 29, 2005: The Seoul National University investigation concludes all of the data was fabricated in the 2005 paper that Hwang’s team published in Science.
Jan. 10, 2006: The Seoul National University investigation concludes that the landmark 2004 paper was fabricated as well. Two days later, Science formally retracts both Hwang papers.
Timeline by Maria Godoy and Joe Palca