Page 5 - De-Extinction: The Science of Bringing Lost Species Back to Life

THE FROZEN ZOO

On November 17, 2015, at the San Diego Zoo, an elderly female
northern white rhinoceros (Ceratotherium simum cottoni)
named Nola began showing signs of illness. She wasn’t eating
much. She became listless. A veterinary team began to watch
her around the clock. On November 22, Nola’s condition
worsened, and the veterinary team made the difficult decision
to euthanize her. With Nola’s death, just three northern white
rhinos were left in the world. That makes the northern white
rhino the most endangered species onEarth.
As conservationists and animal lovers around the world
were learning the news of Nola’s death, Oliver Ryder and
Barbara Durrant were already hard at work. At the San Diego
Zoo’s Institute for Conservation Research, Ryder is director of
genetics and Durrant is director of reproductive physiology.
Whenever an endangered animal dies at the zoo, researchers
race to remove some of the animal’s sperm or eggs and
a bit of its tissue for future research and possibly genetic
engineering. Ryder and Durrant obtained samples of Nola’s
cells. They attempted to collect egg cells, but because of her

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