Elizabeth Ann is the first clone of a US endangered species. She was 33 years in the making

For the first time, scientists have created a clone of an endangered US species - a black-footed ferret named Elizabeth Ann. The researchers used cells from a donor that had been dead for more than 30 years, and the procedure's success could mean not only rescue for one of North America's most endangered mammals, but a watershed moment in conservation biology.

- By Jennifer Leman and Caroline Delbert

After the donor ferret Willa died in 1988, scientists sent her cells to the Frozen Zoo at San Diego Zoo Wildlife Alliance in order to preserve her DNA. Their foresight paid off in November 2020, when Willa's genes were injected into an embryo, zapped 'awake' with a bolt of electricity, and implanted into the uterus of a domestic ferret, who gave birth to Elizabeth Ann in December 2020. 'Cloning, itself, is actually not cutting-edge,' says Ben Novak, lead scientist at the California-based non-profit Revive & Restore, which led the black-footed ferret project. What's really innovative about what we've done is that we reached back in time to bring back something that had been lost.'

The greatest threat to endangered species such as the black-footed ferret is the loss of genetic diversity, Novak says. Genetic variation bolsters a species' fitness, or its ability to bounce back from environmental stresses such as disease, habitat loss, and climate change. Critically, diversity lowers the risk of inbreeding within a species. 'Inbreeding creates problems for [an animal's] fertility, so they end up having fewer offspring, which of course leads to less diversity,' Novak says.

Many endangered species don't see an influx of new genetic material. That's when genetic rescue - a range of techniques that includes everything from low-tech fixes such as introducing new individuals into closed populations, to high-tech solutions like cloning and genetic engineering - - can revive these dwindling species. One of the first steps of genetic rescue, though, is to map a species' genetic information, or genome.