With the advent of gene-editing technology such as CRISPR, scientists have shifted from cloning to genetic engineering as the most promising method for “de-extinction,” or the resurrection of species that have died out.
But unlike cloning, genetic engineering wouldn’t create an exact replica of an extinct species. Instead, the technique would edit an existing animal’s genome so that it resembles that of the desired extinct animal. The challenge is making that proxy as similar to the extinct species as possible.
To explore the limits of this method, researchers attempted to recover the genome of the Christmas Island rat. By comparing fragments of the extinct rat’s genetic instruction book with the genome of a living relative, the Norway brown rat, the team was able to recover about 95 percent of the extinct genome. That sounds like a lot, but it means that 5 percent of the genes were still missing, including some important to smell and the immune system, scientists report in the April 11 Current Biology.
“You can only bring back what you can find. And our point is we can’t find everything,” says Tom Gilbert, an evolutionary biologist at the University of Copenhagen.
