Inbreeding Might have Contributed to Extinction of Woolly Mammoths

A new analysis of mammoth neck bones found that inbreeding was behind the giant mammals' extinction.

Researchers from the Rotterdam Museum of Natural History and the Naturalis Biodiversity Center in Leiden looked at the remains of mammoth and modern elephant neck vertebrae. The team found that woolly mammoths from the North Sea had a 'cervical' (neck) rib. The presence of this extra rib, which is a kind of birth defect, suggests that these mammals probably inbred, which might have contributed to their decline.

"It had aroused our curiosity to find two cervical vertebrae, with large articulation facets for ribs, in the mammoth samples recently dredged from the North Sea. 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," said Jelle Reumer, one of the authors in a news release.

Mammoths belonged to the genus Mammuthus. The woolly mammoth Mammuthus primigenius, which is a close cousin of the modern elephant, is the most famous group of mammoths. The woolly mammoth appeared in the northeastern Siberia around 400,000 years back and was well-adapted to cold with dense fur, short ears and dense undercoat, according to National Geographic.

Climate change and hunting by humans are often cited as reasons for the disappearance of these giant beasts. The latest study shows that a decline in mammoth population probably led to inbreeding, which accelerated the animals' decline.

What is a cervical rib?

From the elegant, long-necked giraffe to the short necked dolphin, all mammals have seven vertebrae in the neck. The cervical rib - a rib attached to cervical vertebra- is an unusual phenomenon and is considered to be a sign of abnormalities rising from inbreeding. The rib itself isn't harmful but its presence shows that the animal faced some environmental stress during early embryonic life.

Note that there are animals such as sloths, manatees and dugongs that have more than seven vertebrae in neck.

The present study on mammoth bones shows that the frequency of cervical rib was probably much higher in these giants than previously known, showing that they faced reproductive stress.

Factors that pushed mammoths into oblivion might have been a disease, famine, cold or all of these factors combined, the news release said.

The study is published in the journal Peer J.