Some experts think mammoths were hunted to extinction by the species that was to become the planet's dominant predator - humans.

Others argue that climate change was more responsible. As the climate warmed, forests spread and replaced the mammoth's grassland habitat. Hunting by humans may have tipped the balance once mammoth numbers had declined significantly.

A 2016 study suggests that one of the last known groups of woolly mammoths died out because of a lack of drinking water. BBC News: Last woolly mammoths 'died of thirst'