21 years ago this month, a wild goat species went extinct — and kicked off a bizarre but ultimately hopeful scientific adventure.

The Pyrenean ibex became extinct in January of 2000, when a falling tree landed on the last surviving member of the species. Three and a half years later, the Pyrenean ibex became extinct for the second time, when a newborn clone gasped her first and last breaths in a Spanish laboratory. Here’s the strange tale of how the Pyrenean ibex became the first extinct species to be cloned and the first species to go extinct twice – and what it means for future conservation efforts.

If A Tree Falls In The Forest, Does It Cause An Extinction?

Scientists know exactly what killed Celia, the world’s last wild Pyrenean ibex. Rangers at a Spanish national park found her on January 6, 2000, lying beneath a fallen tree – an open and shut case. The real mystery, which ecologists may never definitively solve, is how Celia ended up dying alone, when her species once flourished in the mountains of northern Spain and Portugal and southern France.

Several species of ibex – wild mountain goats – live across Europe, Asia, and Africa. They’ve coexisted with humans for a long time; people painted ibexes on the walls of caves in southern Europe 30,000 years ago and at sites in Israel’s Negev Desert at least 10,000 years ago. The subspecies known as the Pyrenean ibex moved into the mountains of northern Iberia and southern France around 18,000 years ago, near the end of the last Ice Age, along with a few other closely related subspecies.

For thousands of years, they thrived. Even in the Middle Ages, historical records tell us that Pyrenean ibex, also called bucardo, grazed the rocky, scrub-dotted mountain pastures in abundance. But their numbers dropped sharply in the 1800s. By 1910 only 40 bucardos remained, sheltered in a national park in northern Spain. Less than a century later, the last of their descendants died – and then she was cloned, and then the clone died.

We’re Not Going To Stock A Theme Park This Way

Conservationists saw what was coming long before Celia’s death, but they still came perilously close to missing their chance. Less than a year before the last Pyrenean ibex died, biologists took skin biopsies from her ears and put the tissue in cold storage. Shortly after her death, Spanish government agencies – think of them as the Spanish counterparts to the U.S. Department of Agriculture and the U.S. Fish and Wildlife Services — working with a private company called Advanced Cell Technology and other teams of researchers, thawed out the frozen samples and started trying to bring the bucardo back from the dead.

The concept is called de-extinction, and Jurassic Park made it look a lot easier than it actually is.

First, if you want an extinct species to walk the Earth again, you need a place to put it. Ecosystems adapt to the loss of a species in several ways; maybe a new species movies in to fill the empty niche, or maybe the whole food web changes so much that the landscape becomes nearly unrecognizable to its old inhabitants. That’s why de-extinction efforts often start by trying to understand the lifestyles and ecological role of extinct species like the thylacine.

Technically, of course, you could create a thylacine, a woolly mammoth, or a bucardo and keep them in captivity – but aside from the ethical arguments, resurrecting a species without reintroducing it to the wild misses most of the point of de-extinction.

The next challenge – the one currently facing efforts to renew the northern white rhinoceros population – is finding a species that can carry cloned embryos to term. You need a fairly close relative whose babies have a similar gestation period and birth weight, and you need to implant the embryo at just the right moment: its stage of development has to coincide with the surrogate mom’s reproductive cycle. And the rather surprising problem is that we don’t know quite enough about the reproductive cycle of living animals like wild goats and southern white rhinos.

Putting one animal’s DNA into a cell is actually the easy part, relatively speaking. When the Spanish researchers tried cloning Celia, they produced nearly 500 cloned embryos, and they implanted 154 of them into female goats (some ibexes and some wild/domestic hybrids). Only 5 of those surrogates ended up pregnant, and only 1 managed to give birth.

When Life Doesn’t Find A Way

For the first few seconds, it looked like the Pyrenean ibex was going to make a comeback. The cloning team delivered Celia’s daughter by Cesarean section, and the newborn burcado had a normal heartbeat, wide open eyes, and actively kicking legs. She just couldn’t breathe.

“Physical defects in the lungs as well as in other organs have also been reported in neonatal cloned sheep that failed to survice,” Jose Folch and his colleagues noted in their 2009 paper on the effort.

Later, scientists learned that the cloned goat had been born with an extra lobe in her left lung, which took up too much space in her chest and kept the left lung from inflating properly. All of her other organs looked normal, and her nuclear DNA was identical to Celia’s, without any potential lethal mutations. After several minutes of “severe respiratory distress,” the Pyrenean ibex passed into extinction for the second time.

What would life have been like for Celia’s daughter if she had survived? It’s hard to say, but the struggling newborn goat could never have completely revived an extinct species on her own. It takes two, as they say – and actually it takes somewhere between 50 and 500, if you want enough genetic diversity to actually keep the species going in the long run.

The best bet would probably have been to cross-breed the cloned burcado with males from another, closely related subspecies of ibex. That way, some of the extinct species’ genetic diversity would at least get passed along, even if the burcado ended up absorbed into another species and therefore technically still extinct. In other words, de-extinction is complicated, not just technically but philosophically.

Folch and his colleagues concluded, “At present, it can be assumed that cloning is not a very effective way to preserve endangered species. […] However, in species as bucardo, cloning is the only possibility to avoid its complete disappearance.” To that end, they urged storing tissue and cell samples from endangered species to give future cloning programs a fighting chance.