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Palaeontology

DNA offers clues to woolly mammoth's demise

By T.K. Randall
March 4, 2017 · Comment icon 13 comments



The mammoth held on until around 4,000 years ago. Image Credit: Charles Robert Knight
An analysis of mammoth DNA has revealed that the species had become wracked with genetic disease.
Study leader Dr Rebekah Rogers from the University of California, Berkeley maintains that just before it went extinct, the woolly mammoth had gone into "genomic meltdown".

The DNA sample in question had come from a mammoth which lived around 4,000 years ago - a time when the species had been all but wiped out save for a few isolated island populations.

To confirm the findings, the researchers also analyzed the DNA of a mammoth from 45,000 years ago which did not show the same signs of genetic disease as its more recent counterpart.
"You had this last refuge of mammoths after everything has gone extinct on the mainland," said Dr Rogers. "The mathematical theories that have been developed said that they should accumulate bad mutations because natural selection should become very inefficient."

The discovery is worrying as similar issues could also plague some of today's endangered species.

"When you have these small populations for an extended period of time they can go into genomic meltdown, just like what we saw in the mammoth," said Dr Rogers.

"So if you can prevent these organisms ever being threatened or endangered then that will do a lot more to help prevent this type of genomic meltdown compared to if you have a small population and then bring it back up to larger numbers."

Source: BBC News | Comments (13)


Recent comments on this story
Comment icon #4 Posted by godnodog 6 years ago
Ice ages are cyclic.  http://earthguide.ucsd.edu/virtualmuseum/climatechange2/01_1.shtml
Comment icon #5 Posted by EBE Hybrid 6 years ago
It sounds as if the last herd of mammoth had a lack of genetic variety, genetic defects becoming more common as they were past from one generation to the next. Norfolf!!!!
Comment icon #6 Posted by Carnoferox 6 years ago
The Wrangel Island population of mammoths had such a high number of genetic defects because they were inbreeding. Genetic bottlenecks happen when animals become stranded on small islands with limited resources. However, these genetic defects did not cause the extinction of the species as a whole.
Comment icon #7 Posted by Farmer77 6 years ago
 Could geographic isolation due to human predation create conditions for sustained interbreeding and genetic degradation? 
Comment icon #8 Posted by oldrover 6 years ago
This is one of the key aspects to a major theory about the megafauna extinction in general. 
Comment icon #9 Posted by Carnoferox 6 years ago
Definitely. That is what happened to the Wrangel Island woolly mammoths. However, it is not known for sure if the geographic isolation was caused by human hunting. A more likely explanation is the gradual disappearance of the mammoth steppe (the natural habitat of the woolly mammoth and numerous other species) and its replacement with boreal forests.
Comment icon #10 Posted by oldrover 6 years ago
It's also one of the factors which played a part in the extinction of the thylacine, and the decline in devil numbers de to DFTD. Not necessarily in the case of the thylacine initially through human agency, and not in the case of the devil. Both instances are the result of geographic isolation. However with the tiger human hunting and land alteration probably exacerbated  the effect.  The same has I believe been postulated for hunting patterns in N America during the late Pliestocene early Holocene. Extinction has lots of little helpers. 
Comment icon #11 Posted by AnchorSteam 6 years ago
Wrangle wasn't always an island, the  Mammoths didn't swim there. Jean Auel said that it was habitat lose that did them in; their environment was the edge of the Glaciers, almost literally. Wrangle may have been the last place in the world they felt comfortable.   
Comment icon #12 Posted by Carnoferox 6 years ago
Woolly mammoths reached Wrangel Island while it was still part of the Bering Land Bridge, then became trapped as sea levels rose again. Habitat loss was a major contributing factor to the extinction of the woolly mammoth. Woolly mammoth habitat wasn't right at the edge of glaciers though, but rather on the wide open steppe. Auel is just an author (not a paleontologist), so I wouldn't use her as a reliable source.
Comment icon #13 Posted by AnchorSteam 6 years ago
Yeah, but I liked her books. 


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