Lost genes, like lost documents, may be lost for good:
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 (SN: 10/7/20). 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.Anna Gibbs, “An extinct rat shows CRISPR’s limits for resurrecting species” at Science News (March 9, 2022)
A separate question, with genes as with documents, is how much do the lost ones matter? If the recreated passenger pigeon was pretty much like the old one, what difference would it make? Shouldn’t the main question be, is this a good ecological idea overall?
What if we brought back the mammoth or the mastodon? What would be the implications for the current ecology?
The paper is open access.
You may also wish to read: Evolutionary biologist Jerry Coyne says they’ll never clone a herd of mammoths. Coyne: What they’d get would be a genetic chimera, an almost entirely Asian elephant but one that is hairier, chunkier, and more tolerant of cold. That is NOT a woolly mammoth, nor would it behave like a woolly mammoth, for they’re not inserting behavior genes. But wait. Are we splitting hairs here?
One Reply to “Researchers: CRISPR is not the big answer to de-extinction”
The article seems a bit short sighted. Obviously if scientists could CRIPR a living genome to become more like an extinct one, then they could – after a few such iterations – replace the “similar” genome with the actual extinct one, at least in principle, thereby truly “resurrecting” the species eventually. If the parent animals are sufficiently similar to give birth to and raise the extinct animal, then it should be possible to get the exact extinct species back. Mind you, there may be some epigenetic tweaking needed, and the reborn animal might not know how to act like the extinct one, but those seem like easy hurdles compared to getting a living animal from an extinct genome.
For the passenger pigeon, a bigger hurdle would be, how many pigeons do you need to make a viable population, before releasing them in the wild? Given that the flocks of millions were decimated and the remaining birds were lost quickly thereafter, they may need a huge minimum population to survive in the wild There is not likely to be enough funding to support the breeding of a million pigeons! Also, would environmentalists object to releasing a million “experimental” birds into the wild?