Forget Mammoths – These Scientists Are Working To Resurrect the Extinct
Dinosaurs went extinct 65 million years ago, mammoths 4,000 years ago, and the Christmas Island Rat 119 years ago. Since becoming a popular concept in the 1990s, de-extinction efforts have focused on grand animals with mythical stature, but in a paper published March 9, 2022, in the journal Current Biology, a team of paleogeneticists turn their attention to Rattus macleari, and their findings provide insights into the limitations of de-extinction across all species.
De-extinction work is defined by what is unknown. When sequencing the genome of an extinct species, scientists face the challenge of working with degraded 
Maclear’s rat (Rattus macleari) is an extinct large rat endemic to Christmas Island in the Indian Ocean. Credit: Joseph Smit, Proceedings of the Zoological Society of London 1887
After the DNA has been sequenced as well as possible and the genome is matched up against the reference genome of the living species, the scientists identify the parts of the genomes that don’t match up and, in theory, would then use CRISPR technology to gene edit the DNA of the living species to match that of the extinct one. The brown-rat-to-Christmas-Island-rat scenario is a particularly good test case because the evolutionary divergence is similar to that of the elephant and the mammoth.
Though the sequencing of the Christmas Island rat was mostly successful, a few key genes were missing. These genes were related to olfaction, meaning that a resurrected Christmas Island Rat would likely be unable to process smells in the way as it would have originally. “With current technology, it may be completely impossible to ever recover the full sequence, and therefore it is impossible to ever generate a perfect replica of the Christmas Island rat,” says Gilbert.
“It is very, very clear that we are never going to be able to get all the…
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