While one group of scientists is working to de-extinct the woolly mammoth, another is looking at the last days of possibly the last small herd of the species before extinction. Let’s hope they get together at some point so the poor animal doesn’t suffer the same fate again.
As I looked at the sequence data, it became very clear that the Wrangel mammoth had an excess of what looked like bad mutations.
In their study published in PLOS Genetics, biologists Rebekah Rogers and Montgomery Slatkin at the University of California, Berkeley, take us back 4,000 years to Wrangel Island off the Siberian coast where the last 300 woolly mammoths lived, long after the mainland mammoths (Mammuthus primigenius) went extinct. They compared the DNA from one of these island mammoths with that from a mammoth in its prime from 45,000 years ago. The differences were astonishing … and sad.
Many of the changes in the mammoth’s DNA that Rogers and Slatkin found can be translated into visual depictions of the last mammoths, and they look nothing like the massive beasts drawn in natural history books. Today’s elephants, living relatives of the mammoths, depend on urine and their sense of smell for mating and determining herd hierarchy. The researchers saw a breakdown of these proteins in the mammoth DNA, which meant they lost their sense of smell and had severe urinary tract problems, resulting in management problems that reduced the size of the herd and health issues that reduced the size of the mammoths themselves.
It gets worse. The DNA showed a breakdown in genome that made the woollies woolly, indicating that their signature heavy wool-like coats had turned satiny, shiny, thin and translucent – not what they needed to keep warm in Siberia.
It’s easy to blame this breakdown and eventual extinction on inbreeding, but Rogers says the DNA tells a different story, which she describes as a “nearly neutral genome evolution.”
What did happen was that the population was simply small, and under these circumstances any mammoth was better than no mammoth at all. Bad mutations that would normally be weeded out weren’t removed from the population because of reduced competition.
Does this let human hunters off the hook as the probably cause of woolly mammoth extinction? Not hardly. It just adds another piece to the puzzle, which already includes human intervention and climate change. However, Rogers says it does send a warning to both the researchers working on de-extincting the woolly mammoth – thus creating an artificially small population – and the keepers of today’s rapidly–dwindling elephant herds.
Even though we can improve the number of individuals in endangered populations, their genomes may still bear the hallmarks of genomic meltdown, which will be difficult to undo.
While the opposite makes for better movie plots, in real life it’s always a good philosophy to consider what you may have to ‘undo’ before you ‘do’.