In the summer of 2013, starfish began disappearing from waters off the coasts of North America, where they have historically dominated, according to the Guardian.

When scientists investigated the matter, they discovered that various starfish species were dying en masse, their bodies disintegrating and melting from an unknown virus. Soon, up to 80% of certain ochre sea star species had died.

They believe that the virus afflicting the starfish had always been around, but that warming ocean temperatures from climate change allowed it to proliferate and terrorize starfish, according to the Guardian.

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But five years later, the starfish seem to have developed a genetic resistance to the virus in what is being hailed as one of the fastest, real-time examples of evolution in history, according to a new study published in the Proceedings of the National Academy of Sciences of the United States of America (PNAS).

In fact, there’s a 74-fold increase in the number of juvenile starfish in certain coastal areas compared to when the virus was at its worst.

The authors of the study analyzed the DNA of juvenile starfish and compared it with starfish that had succumbed to the virus. They found a key genetic difference, suggesting that rapid natural selection allowed a resistance to develop.  

“When you’ve removed a whole bunch of them, you’ve shifted the whole genetic diversity of that population,” Chris Mah, a researcher at the Smithsonian Institution and a starfish expert, told the Guardian. “In other words, to put it in human terms, if you wiped out a huge chunk of the human species, you would change the genetic makeup of humans.”

The new research suggests that other species such as coral could develop similar genetic resilience in the face of extreme environmental conditions.

Read More: 5 Coral Reefs That Are Dying Around the World

However, the authors are quick to warn that this is likely an isolated event, and that the range of threats facing marine animals are overwhelming many species.

“The concern is that marine disease, extreme environmental events, and the frequency of those are on the rise,” Lauren Schiebelhut, the lead author, told the Guardian. “If we have too many extreme events in a row, maybe that becomes more challenging for species to respond to.”

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