Inbreeding possible cause of woolly mammoth extinction

Researchers recently examined the remains of two woolly mammoth remains found in the North Sea. What they found is quite interesting. Both specimens, who were most likely the last woolly mammoths in this area, had cervical ribs (ribs attached to the vertebrae in the neck). Upon further analysis, researches discovered that around one third of the total population of found woolly mammoth remains have this condition. This number is very high compared to their modern day relative, the elephant, in which this event only occurs in about 3% of the population. What could cause this high percentage of abnormal bone structure? In humans, cervical ribs are caused by inbreeding and adverse environmental conditions during pregnancy. Researches believe that the same is true here. Perhaps disease, famine, or the extreme cold  caused a decline in the woolly mammoth population size, causing a higher percentage of inbreeding. Or, perhaps the population size was small from the beginning, causing inbreeding to be a large factor throughout their existence. Either way, this discovery sheds new light on the vulnerability of the woolly mammoth species.  The article is linked below.

Extraordinary incidence of cervical ribs indicates vulnerable condition in Late Pleistocene mammoths