What are the Andes?

The longest continental mountain range on Earth, some 7,000 kilometres down the western edge of South America through seven countries. They are being pushed up by the Nazca plate sliding beneath the continent, which also supplies the volcanoes and makes this one of the most seismically violent places anywhere - the largest earthquake ever recorded, magnitude 9.5, struck Chile in 1960.

They are also where a startling amount of the world's food was domesticated. The potato comes from the Andes, where thousands of varieties are still grown at different altitudes as insurance against any one failing, along with tomatoes, quinoa, and the domestication of the llama and alpaca. Europe's population growth after 1700 is not separable from the arrival of the potato.

The high plateau has shaped its people physically. Andean populations have adapted to thin air with higher haemoglobin concentrations, a different route from Tibetans, who evolved a separate solution involving greater breathing rates and blood flow - and the Tibetan variant appears to have been inherited from Denisovans, an extinct human group. Two populations, two mountain ranges, two entirely different genetic answers to the same problem.