A Short History of Cloning
From frog embryos in the 1950s to current stem-cell research: a careful timeline of the experiments and decisions that shape today’s debate.
First embryo splitting in sea urchins
Hans Driesch separates two-cell sea-urchin embryos and shows each cell can give rise to a complete larva — a very early conceptual precursor to cloning.
Salamander nuclear transfer
Hans Spemann proposes a thought experiment about transferring a nucleus into an enucleated egg. The technical groundwork would take decades.
Briggs & King clone frog embryos
Robert Briggs and Thomas King carry out the first successful nuclear transfer experiments in frog embryos, demonstrating that an embryonic nucleus can direct development.
Gurdon’s tadpoles
John Gurdon shows that nuclei from differentiated frog cells can be reprogrammed by an egg to produce tadpoles. The result will later earn him a share of the 2012 Nobel Prize in Physiology or Medicine.
First mouse embryonic stem cells
Independent groups derive embryonic stem cells from mice, opening decades of work on cell pluripotency and a foundation for later stem-cell medicine.
First mammalian embryo nuclear transfer
Steen Willadsen reports cloning a sheep from early embryonic cells, establishing that mammalian nuclear transfer is feasible.
Dolly the sheep
Ian Wilmut, Keith Campbell, and colleagues at the Roslin Institute announce a sheep cloned from an adult somatic cell. The result forces biology to revisit assumptions about whether differentiation could be reversed.
National Bioethics Advisory Commission report (US)
The US commission recommends a moratorium on attempts to create a child by somatic cell nuclear transfer.
First human embryonic stem-cell lines
James Thomson’s group derives human embryonic stem-cell lines from donated IVF embryos, opening the modern era of human regenerative-medicine research.
National stem-cell policy debates
Governments around the world develop their first dedicated stem-cell and cloning regulations, including the UK’s Human Reproductive Cloning Act 2001.
UN Declaration on Human Cloning
The UN adopts a non-binding declaration calling on member states to prohibit forms of human cloning incompatible with human dignity.
Induced pluripotent stem cells
Shinya Yamanaka’s group reprograms adult mouse and then human cells into induced pluripotent stem cells (iPSCs), reducing the research case for therapeutic cloning.
Nobel Prize for cellular reprogramming
John Gurdon and Shinya Yamanaka share the Nobel Prize for the discovery that mature cells can be reprogrammed to become pluripotent.
Human stem cells via SCNT
Researchers report deriving human embryonic stem-cell lines via somatic cell nuclear transfer — a research milestone, not a step toward producing a baby.
Cloned macaques
Chinese researchers report two macaques produced by somatic cell nuclear transfer, the first cloning of non-human primates by that method, reigniting policy debate.
Policy era
Reproductive human cloning remains broadly prohibited. The active research agenda is dominated by stem cells, gene editing, and regenerative medicine rather than reproductive cloning.
How to read this timeline
Two threads run through the history of cloning. One is technical: a long chain of experiments showing that cells could be moved, reprogrammed, and coaxed into doing things textbooks had said they could not do. The other is political and ethical: a slower, less heroic process of governments, ethics committees, and international bodies working out which of those technical possibilities should actually be pursued.
Both threads are still active. The science has not finished, and the law has not settled. What has changed is that today’s frontier is less about reproductive cloning and more about gene editing, stem-cell therapy, and the careful study of how cells acquire and lose identity.