On April 20, 2014 I posted an entry citing research that humans may not have been the main cause of the extinction of the mammoths. The article quoted below provides further evidence:
(p. D2) Many woolly mammoths from the North Sea had a superfluous rib attached to their seventh vertebra, a sign that they suffered from inbreeding and harsh conditions during pregnancy, researchers report.
This may have contributed to their eventual extinction, say the scientists who looked at fossil samples that date to the late Pleistocene age, which ended about 12,000 years ago.
. . .
Woolly mammoths died out 12,000 to 10,000 years ago, when flowery plant covers disappeared from the tundra. Human hunting may also have contributed to their demise.
But the cervical ribs are a clear indication that “they were already struggling before that,” Dr. Galis said.
For the full story, see:
SINDYA N. BHANOO. “Observatory; In Extra Rib, a Harbinger of Mammoth’s Doom.” The New York Times (Tues., April 1, 2014): D2.
(Note: ellipsis added.)
(Note: the online version of the commentary has the date MARCH 31, 2014.)
The mammoth research summarized above was published in:
Reumer, Jelle W.F., Clara M.A. ten Broek, and Frietson Galis. “Extraordinary Incidence of Cervical Ribs Indicates Vulnerable Condition in Late Pleistocene Mammoths.” PeerJ (2014).