Endangered horse cloned from frozen cells

Reborn: The cloned horse was born on the 6 August to a surrogate mother in Texas, US. © Scott Stine

Should we bring back extinct species? Cells preserved for 40 years have been used to clone an endangered wild horse, but some scientists ask whether cloning is really the solution.

Kurt is one of a kind. The latest video of this newborn Przewalski’s horse shows him frolicking happily next to his mother. But she is not his genetic parent. He is an exact copy of his father and the world’s first cloned wild horse.

This is the astonishing result of 40 years of foresight and cloning technology. A century ago there were only 12 Przewalski’s horses left, and although numbers have recovered, the species is still critically endangered. Inbreeding and a lack of genetic diversity threaten its long-term survival.

A clone of a stallion who died in 1998, Kurt will reintroduce lost genetic material into the gene pool. This will strengthen future generations against disease and environmental change. But cloning horses is only the start of what this technology might achieve.

The foal is named after Kurt Benirshke, the founder of the Frozen Zoo in San Diego, California. Forty-five years ago, Benirshke began freezing the cells of endangered species long before cloning technology existed. The zoo has collected biopsies from over a thousand species, kept at minus 196 °C in liquid nitrogen.

Benirshke’s motto was: “You must collect things for reasons you don’t yet understand,” and this genetic treasure trove had to wait for biotechnology to catch up. In 1996, Dolly the sheep became the first mammal to be cloned, followed by the first cloned pet, CopyCat, in 2001. There were setbacks. An attempt to resurrect the extinct Pyrenean ibex in 2003 produced a kid that only survived for10 minutes.

As the science improved, conservationists looked further back in time to rescue animals that had disappeared hundreds or thousands of years ago. Gene editing now allows scientists to reprogramme a pigeon to create an extinct passenger pigeon, or even to edit an elephant’s DNA to make a woolly mammoth.

However, some think we need to stop and ask whether we should be cloning animals at all. The prospect of safari parks populated by mammoths and sabretooth tigers may sound exciting, but critics say cloning for entertainment will lead to the prehistoric disaster imagined in the film Jurassic Park when a power failure causes the park's cloned dinosaurs to run loose.

Palaeontologist Michael Archer says “we have an obligation” to reverse the mass extinction caused by humans over the last ten thousand years. For example, hunting has reduced the northern white rhino to a mere two surviving animals. DNA from the Frozen Zoo can give the rhino a second a chance.

But the environmental philosopher Glenn Albrecht says that without homes for these cloned animals, this “whole exercise is futile and a gross waste of money”. Many animals are threatened or have died out because of a loss of habitat. Reviving such animals without restoring their ecosystems, Albrecht argues, makes no sense.

For this reason, the ecologist Sergey Zimov is building Pleistocene Park in Siberia. The park is an ambitious project to counter climate change and replace tundra with the Ice Age grasslands where the woolly mammoth once roamed – and one day, thanks to cloning, where it may roam again.

But should we bring back extinct species?

A new lease of life

Some say no, cloning is playing God and will end badly. Natural selection means the strong survive, and the weak die out. Cloning interferes with this process and will not work. Even if we successfully clone extinct or endangered animals, they would not survive in the wild. And if they do, they will disrupt existing ecosystems and endanger other species.

Others say yes, we don’t just have a duty to do it: our planet depends on reversing the rate of extinction. Humans have degraded habitats and killed off thousands of species. As biodiversity declines, the remaining species become even more vulnerable to disease, environmental disaster and climate change. By diversifying the gene pool, cloning may safeguard the future of life on Earth.

You Decide

  1. What endangered or extinct animal would you clone?
  2. Do we have a moral duty to rescue endangered species from extinction?


  1. Draw your own safari park of extinct animals brought back to life.
  2. Life on Earth faces mass extinction and you only have room for five species in your frozen zoo. Which species are you going to preserve and why? Write a page explaining your choices.

Some People Say...

“In pushing other species to extinction, humanity is busy sawing off the limb on which it perches.”

Paul R. Ehrlich, American biologist

What do you think?

Q & A

What do we know?
It is generally agreed that the rate of species extinction is accelerating. Ten thousand years ago, roughly one species disappeared every month, but conservationists believe human activity is now wiping out between 150 and 200 species every day. There are over 32,000 critically endangered species, including the European hamster, the North Atlantic right whale and several species of lemur.
What do we not know?
One main area of debate is around whether a clone is really the same as the original. Identical twins are genetic clones, but nurture and experience raise two separate individuals. And although cloning technology can potentially edit an elephant’s DNA to look like a mammoth, is the cloned mammoth the real thing? Some argue that an animal only exists as part of an ecosystem and a cloned animal is just an exotic curiosity, without the habitat in which it evolved.

Word Watch

Przewalski’s horse
This species split from the domestic horse 45,000 years and was once thought to be the only surviving species of wild horse. Recent studies now suggest the Przewalski’s horse is descended from an animal domesticated by the Botai culture of Central Asia, 5,500 years ago.
Genetic diversity
A lack of variation in the gene pool means that a new disease will affect the entire population in the same way. An endangered species may appear to recover but then be wiped out by a disease or change in environment.
Samples of tissue removed for further investigation. In this case skin tissue can be used to create embryonic stem cells. In the example of the cloned horse, the nucleus of the mother’s egg cell is replaced with a nucleus containing DNA from the frozen biopsy.
Pyrenean ibex
The last member of this species of wild mountain goat died in 2000. For a brief ten minutes, it became the first extinct species to be brought back to life.
Passenger pigeon
In the 1700s there were an estimated three billion passenger pigeons in North America. Hunting and habitat loss decimated the population. In 1914, Martha, the last pigeon. died in Cincinnati Zoo.
Woolly mammoth
Once common in the northern hemisphere, the last of these furry giants died out around four thousand years ago. Because so many carcasses were frozen during the Ice Age and preserved in the permafrost, they offer scientists the best opportunity to resurrect a prehistoric beast.
Jurassic Park
Geneticists often complain that the 1993 dinosaur disaster movie is mentioned whenever people debate animal cloning. They say the tyrannosaurus rex died out 65 million years ago, left no genetic material behind and won’t be coming back.
Someone who studies the fossilised remains of extinct species. Scientists have estimated that as many as four billion species have lived on Earth and 99.9% of them are now extinct.
Pleistocene Park
Around ten thousand years ago Siberian grassland was replaced by tundra and coniferous forests. Bison, musk oxen and wild horses have been reintroduced to a remote part of Russia to gradually transform the land back into an Ice Age savanna.


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