De-extinction Scientists Set to Bring Back Enormous Long-Lost Rat

De-extinction scientists are set to bring an enormous, long-lost rat back from the dead.

The Christmas Island rat, Rattus macleari, also known as the Maclear's rat, was native to Australia. It could grow to around 1.5 feet from head to tail.

The rats were wiped out about 120 years ago in a mass extinction event between 1899 and 1908, as diseases brought by European ships swept through the population. The rodent had large and powerful teeth, capable of feasting on the island's red crabs. It had long, thick fur and black whiskers measuring about three inches in length.

Researchers are now hoping to resurrect the lost species after obtaining almost all of the Christmas Island rat's genome. They found that the extinct rat shared about 95 percent of its genes with the living, Norway brown rat. Their findings are published in the journal Current Biology.

Tom Gilbert, from the University of Copenhagen, is the lead evolutionary geneticist on the project. He said this means scientists have "quite a nice test model" to begin de-extinction efforts for the species. "It's the perfect case because when you sequence the genome, you have to compare it to a really good modern reference," he said in a statement.

Editing DNA

The scientists worked to compare the extinct rat's genes with the genome of the Norway brown rat. From there, they identified the parts of the genomes that don't match up, and then used CRISPR technology to edit the DNA of the living species, to match that of the extinct one.

Although this was mostly successful, a few key genes were missing. The missing genes mean that a resurrected Christmas Island rat would be unlikely to process smells in the same way its descendants would have.

Gilbert told Newsweek that with current technology it may be completely impossible to ever recover the full sequence.

"Because of the combined problems of DNA degradation and evolutionary divergence...you'll never (through editing) be able to get back exactly what went extinct. We will have to accept they will be some kind of hybrid of the extinct form and the living relative," he said. "And then with that information at hand (especially if you run the analysis we did) you can then decide if it's worth your time/money/effort to create whatever you are working on."

Gilbert now plans on editing the black rat genome, to change it to a Norway brown rat, before attempting to resurrect the long-lost rat.

Scientists believe the Norway brown rat and the Christmas Island rat have a similar evolutionary divergence to that of an elephant and the extinct wooly mammoth. This means, if successful, this experiment could help with future de-extinction efforts for other animals.

Gilbert said in a press release that the technology may be enough to edit elephant DNA to make the animal hairy, and able to live in the cold, although it would not be an exact match.

"If you're making a weird fuzzy elephant to live in a zoo, it probably doesn't matter if it is missing some behavioral genes," he said. "I think it's a fascinating idea in technology, but one has to wonder if that's the best use of money as opposed to keeping the things alive that are still here."

Update 03/11/22 at 3:35 a.m. ET; This article has been updated to include quotes from Tom Gilbert