New research theorizes that woolly mammoths, ancestors to the common elephant, were not killed off by a giant meteor or overhunting but instead were the victims of inbreeding and an unfortunate climate.
Scientists from the Natural History Museum of Rotterdam and Utrecht University began by examining the fossil collections owned by several European museums in an effort to explain the extinction of the woolly mammoth, reports Live Science . They focused on the neck vertebrae of the mammals, and found that three out of nine woolly mammoths had neck vertebrae connected to cervical ribs, whose presence is linked to disastrous developmental delays and malformations. Further examination of the fossils showed that the cervical ribs are ten times more common in woolly mammoths compared to modern elephants.
"We knew these were just about the last mammoths living there, so we suspected something was happening. Our work now shows that there was indeed a problem in this population," says lead researcher Jelle Reumer of the mammoths found near the North Sea. Reumer and his team have two theories for why so many woolly mammoths were born with the cervical rib. “A combination of inbreeding and harsh conditions may be the most likely explanation for the extremely high incidence of cervical ribs,” the research team concluded in the study . The LA Times reports that in humans, 90% of infants born with a cervical rib die before they reproduce. Applied to woolly mammoths, the cervical rib birth defect meant shorter lifespans and a much lower chance of producing offspring, leading to extinction.