If the Arctic permafrost melts, greenhouse gasses equivalent to burning all of the world's forests two-and-a-half times over could be released.
Russian researchers have found what they think is a spear made from a mammoth tusk lodged inside the ribs of mammoth remains.
Evidence suggests ancient humans may have hunted the mammoth and then stored the meat at the bottom of a pond.
Scientists dig up twice as many male mammoths as females, but that doesn't mean their population was so skewed.
Mammoth ivory, like modern elephant ivory, is durable and doesn't splinter easily, and so makes a good spear for hunting.
They are using different approaches to the de-extinction issue—and only one can be first.