Why Black Bears Sleep in Trees

The ancestors of modern North American bears evolved in Asia during the Pleistocene, wandering over to Alaska during several appearances of the Bering land bridge, between the Bering and Kamchatka Peninsulas. Advancing and receding glaciers, fueled by evaporating sea water, caused ocean levels to alternately drop and rise, exposing and resubmerging the Bering Strait. The ancestors of black bears came across half a million years ago, and it is suspected that black bears adapted to climbing tr...

 Nature Doesn't Need Our Help to Destroy the Earth

For me, the most paralyzing news was that Nature was no conservationist. It needed no help from us in taking the planet apart and putting it back together some different way, not necessarily improving it from the viewpoint of living things. It set fire to forests with lightning bolts. It paved vast tracts of arable land with lava, which could no more support life than big-city parking lots. It had in the past sent glaciers down from the North Pole to grind up major portions of Asia, Europe, a...

 The Science on the Path

A weed plucked at the side of the path might have found its way to the New World in a seventeenth century sailing ship. Scratches on a rocky ledge evoke colossal mountain-building events on the other side of the world millions of years ago that modified the planet's climate and caused glaciers to creep across New England. The oxygen atoms I suck into my lungs were forged in stars that lived and died long before the Earth was born. It is something of a cliche to say that everything is connecte...