A strange thing happened in northwestern Europe half a million years ago.
People started popping up in the archeological record, leaving behind stone tools and butchered bones.
Or, if not actual people, at least close evolutionary cousins: homo erectus, homo heidelbergensis, homo antecessor, the first Europeans. Their presence there was a mystery.
Living in rudimentary families built around male-female pair bonds, they pushed northwards across France, past 50 degrees latitude into Germany, even to the coast of Britain, which was then accessible by land across the chalk ridge whose remnants today are famous as the White Cliffs of Dover.
This has baffled anthropologists. Why would a creature that arose in the lush warmth of Africa, foraging plentiful plants and hunting abundant small game, decide to strike out for such a miserable place, with a climate like modern Scandinavia, where snow covers the land half the year, the sun sinks low in the sky, and the most plentiful game meat comes from massive ungulates that migrate over hundreds of miles?