Researchers recently noticed that the remains of woolly mammoths from the North Sea often possess a ‘cervical’ (neck) rib — in fact, 10 times more frequently than in modern elephants (33.3 percent versus 3.3 percent). In modern animals, these cervical ribs are often associated with inbreeding and adverse environmental conditions during pregnancy. If the same factors were behind the anomalies in mammoths, this reproductive stress could have further pushed declining mammoth populations towards ultimate extinction.