Dolly, the world’s most famous and controversial sheep, was born twenty years ago – on July 5, 1996 to be precise. She was the first mammal to enter the world following a process of reproductive cloning, making the event a spectacular scientific breakthrough.
To create Dolly, researchers at the Roslin Institute in Scotland employed a technique known as somatic cell nuclear transfer (SCNT). With SCNT, DNA from the nucleus of an ordinary cell - obtained from anywhere in an animal’s body - is transferred into an enucleated oocyte (egg cell), typically from a different animal.
In Dolly’s case, her DNA came from one sheep’s mammary cell; it was implanted into an egg from another sheep; and the resulting tiny biological entity was implanted into the uterus of yet a third sheep, where it grew until birth.
The result of SCNT is a creature with almost the same genetic potential as the one providing the nuclear DNA. SCNT is thus a powerful, and often effective, form of animal cloning.
Dolly is born! Announcement and reaction
Subsequently, in February 1997, Ian (now Sir Ian) Wilmut and his research team at the Roslin Institute announced Dolly’s birth in the prestigious science journal Nature. This provoked political and ethical debates that have never truly stopped.
Public discussion of cloning gradually receded in prominence as new issues arose to dominate the airwaves and the headlines, notably the threat of jihadist terrorism following the attacks on September 11, 2001. But issues relating to cloning technology remain crucial to debates over biomedical research and its regulation.
The announcement – with a description of the method used to bring Dolly into existence – triggered a feverish worldwide response because of the possible implications for human cloning. It was immediately obvious that SCNT could, in principle, be used to create human babies. Across the world, many countries banned human cloning - often with significant punishments, such as lengthy jail terms, even for attempting such a thing.
The case against cloning
The actual arguments against human cloning are extremely varied, and I cannot elaborate them all here. (I go into more of them, and in far more depth, in my 2014 book, Humanity Enhanced: Genetic Choice and the Challenge for Liberal Democracies).
One common claim is that bringing children into the world in this way is somehow a violation of the natural order, or of human dignity; or perhaps it would be an act of “playing God”. Unfortunately, it can be very difficult to pin down precisely what any of these claims really mean in the context of bioethical debate. I am, for example, sceptical about the existence of anything that can correctly be called “human dignity”.
Some critics fear that children created via SCNT would be subjected to unfair expectations of duplicating the talents and achievements of whoever provided their nuclear DNA. Sometimes the critics speak in terms of the autonomy of the child being violated, diminished or denied, although it can be very difficult to spell out exactly what this amounts to. In Humanity Enhanced, I challenge the idea that children conceived through SCNT would have their autonomy violated – or would somehow lack or lose autonomy – in any sense inapplicable to “ordinary” children.
Some critics worry about a larger social effect, or even an effect on our species, if cloning restricted the diversity of children being born (perhaps because parents and doctors might look for donors with a narrow range of characteristics, such as possessing high intelligence and meeting certain standards of physical beauty).
Yet other arguments acknowledge that reproductive cloning in itself might not have a great social or species-wide impact; however, it’s claimed, cloning could place human societies on a slippery slope toward accepting even more radical technological interventions such as genetic engineering of human traits. On one version of the approach, this would, in turn, set us upon a path to unequivocally horrible social outcomes. Thus cloning supposedly confronts us with a slippery slope to another slippery slope … which seems like a tenuous style of argument.
Though some of these fears may have an element of truth, they are all exaggerated. In my view, which I’ve defended in Humanity Enhanced and other publications, human cloning would not be a seriously worrying action if we could carry it out safely.
To some extent, however, all of this is moot. Over the past twenty years, we have enjoyed success in cloning many mammalian species, but no one has cloned a human being. Indeed, we have been frustrated in efforts to clone other primates such as apes and monkeys.
In the upshot, human reproductive cloning is not yet feasible, and indeed there’s no current prospect that it could be carried out effectively and safely in the foreseeable future. Even if we did conceive a human embryo through SCNT, and we then managed to bring it to term, the odds are very high that the result would be a seriously deformed child.
That’s a good pragmatic reason not to make attempts until we know a lot more, and even then we’d need to have developed the technology to a point where we are about as likely as with ordinary births to end up with a healthy baby.
I don’t rule out that someone might accomplish this technological feat one day, but, once again, there is no sign of it happening. Nor is it what SCNT research is really about from the point of view of reputable medical researchers. The real action is with what is known as “therapeutic cloning”. Allow me to explain.
Reproductive and therapeutic cloning
So far I’ve focused on “reproductive cloning”, and more specifically on human reproductive cloning: the postulated use of SCNT (or any other technique that might have a similar result) to bring about the birth of a human child.
By contrast, the expression “therapeutic cloning” refers to the creation of human embryos by SCNT for some other purpose, such as for biomedical research or for harvesting cells or tissues to be used in therapies.
Although some ethical issues are raised with therapeutic cloning – including a concern that the associated research destroys human embryos – the idea has been obtaining legal acceptance in some countries, usually subject to tight government regulation. If we start to see impressive results from therapeutic cloning, with new therapies emerging from the research, I expect that it will eventually obtain the same wide acceptance that IVF – in vitro fertilization – now enjoys in Western countries. (It’s not that long ago that IVF was also widely regarded as abhorrent.)
More generally, people come to embrace new technologies, even those that initially seemed shocking and “unnatural”, once concrete benefits become clear.
Twenty years later
Two decades later, I’m not sure that the ethical arguments advanced for and against human cloning are greatly different from those we saw back 1997. However, the early debate was very one-sided. The initial response to the dramatic Nature article by Wilmut et al. was largely one of fear, mingled with disgust, with too little rational reflection. Since then, the fear-mongering has partly died down, but not before a great deal of draconian legislation was enacted across the world. Little chance was given for calmer voices - or any dissenting voices - to be heard before governments took action.
As it seems to me, calmer voices eventually won the academic debate. There is a strong sense, within the field of secular bioethics, that the early arguments against human reproductive and therapeutic cloning were flawed. However, dissenters lost the political debate almost before it began. Politicians, journalists, many academics, and the general public in our Western liberal democracies greeted the very idea of human cloning with a cascade of hostility.
The expressions of fear, disgust, and moral outrage appeared immediately; in response, highly illiberal laws were enacted without due consideration of the issues.
But more reasonable people are slowly winning back the central political ground, gradually making the public case that technologies based on SCNT may bring many benefits. That, perhaps, will be the story of the next twenty years.
Dolly and her surrogate mother
Dolly was part of a series of experiments at The Roslin Institute that were trying to develop a better method for producing genetically modified livestock. If successful, this would mean fewer animals would need to be used in future experiments. Scientists at Roslin also wanted to learn more about how cells change during development and whether a specialised cell, such as a skin or brain cell, could be used to make a whole new animal.
These experiments were carried out at The Roslin Institute by a team led by Professor Sir Ian Wilmut. Because of the nature of the research, the team was made up of many different people, including scientists, embryologists, surgeons, vets and farm staff.
Dolly was cloned from a cell taken from the mammary gland of a six-year-old Finn Dorset sheep and an egg cell taken from a Scottish Blackface sheep. She was born to her Scottish Blackface surrogate mother on 5th July 1996. Dolly’s white face was one of the first signs that she was a clone because if she was genetically related to her surrogate mother, she would have had a black face.
Because Dolly’s DNA came from a mammary gland cell, she was named after the country singer Dolly Parton.
Learn more about cloning with our cloning FAQs.
Why was Dolly so important?
Dolly was important because she was the first mammal to be cloned from an adult cell. Her birth proved that specialised cells could be used to create an exact copy of the animal they came from. This knowledge changed what scientists thought was possible and opened up a lot of possibilities in biology and medicine, including the development of personalised stem cells known as iPS cells.
However, Dolly was not the first ever cloned mammal. That honour belongs to another sheep which was cloned from an embryo cell and born in 1984 in Cambridge, UK. Two other sheep, Megan and Morag, had also been cloned from embryonic cells grown in the lab at The Roslin Institute in 1995 and six other sheep, cloned from embryonic and foetal cells, were born at Roslin at the same time as Dolly. What made Dolly so special was that she had been made from an adult cell, which no-one at the time thought was possible.
Dolly was announced to the world on 22nd February 1997 to a frenzy of media attention. The Roslin team chose to make the announcement at this time to coincide with the publication of the scientific paper which describes the experiments that produced her. Dolly captured the public’s imagination – no small feat for a sheep – and sparked a public debate about the possible benefits and dangers of cloning.
Dolly meets the world’s media. Image copyright: Murdo Macleod
In the week following the announcement, The Roslin Institute received 3,000 phone calls from around the world.
When Dolly was one year old, analysis of her DNA showed that her telomeres were shorter than would be expected for a normal sheep of the same age. Telomeres are ‘caps’ on the ends of DNA molecules that protect the DNA from damage. As an animal or person ages, their telomeres become progressively shorter, exposing the DNA to more damage.
It’s thought that Dolly had shorter telomeres were because her DNA came from an adult sheep and the telomeres had not been fully renewed during her development. This could have meant that Dolly was ‘older’ than her actual age. However, extensive health screens on Dolly at the time did not find any conditions which could be directly related to premature or accelerated ageing.
Dolly and Bonnie
Dolly spent her life at The Roslin Institute and, apart from the occasional media appearance, led a normal life with the other sheep at the Institute. Over the years Dolly had a total of six lambs with a Welsh Mountain ram called David. Their first lamb, Bonnie, was born in April 1998, twins Sally and Rosie were born the following year and triplets Lucy, Darcy and Cotton the year after.
After Dolly gave birth to her last lambs in September 2000, it was discovered that she had become infected by a virus called Jaagsiekte sheep retrovirus (JSRV), which causes lung cancer in sheep. Other sheep at The Roslin Institute had also been infected with JSRV in the same outbreak.
In 2001, Dolly was diagnosed with arthritis after farm staff noticed her walking stiffly. This was successfully treated with anti-inflammatory medication, although the cause of the arthritis was never discovered.
Dolly continued to have a normal quality of life until February 2003, when she developed a cough. A CT scan showed tumours growing in her lungs and the decision was made to euthanise Dolly rather than risk her suffering. Dolly was put to sleep on 14th February 2003, at the age of six.
Where is Dolly now?
After her death The Roslin Institute donated Dolly’s body to the National Museum of Scotland in Edinburgh, where she has become one of the museum’s most popular exhibits. Dolly is back on display in the museum after an extensive gallery refurbishment, alongside an interactive exhibit on the ethics of creating transgenic animals featuring current research from The Roslin Institute.
National Museums Scotland blog post – ‘Goodbye Dolly’