On waking up one day this January in Valencia, I was cheered by seeing from the window the burning colour of oranges against green leaves. They were just ripe for harvest. For breakfast, I was offered toast smeared with garlic and tomato, sploshed with olive oil.
There’s an east-west line across Spain separating the North, cold in winter, where oranges do not grow. There’s another line, north-south, that separates off the tomato-toast breakfast in the eastern Levante. In Valencia, I was in the orange-tomato sector. Had I travelled west, I would have found another breakfast line, separating toast with butter or jam in the North from flavoured lard in the South. If you wanted, you could map Spanish breakfasts not only against January temperatures but also against dialect, forestation, building materials (stone, brick, mud), pig-rearing and hats (berets, sombreros).
Maxim Samson is not quite as interested in breakfast as I am. In fact, I don’t think he mentions the meal, but he takes 30 invisible lines in different places round the world and teases out their effects. The longest is the International Date Line (and its daddy, the Prime Meridian through Greenwich). The author, a Chicago professor of geography, lauds it as a “rare example of a globally accepted standard that has never been officially defined by an international treaty”. At noon at Greenwich, it’s midnight on the opposite side of the globe, but a different day east and west on the imaginary date-line there.
It was fortunate that the great powers acquiesced in Greenwich hosting the Prime Meridian – though France insisted on describing GMT as “Paris mean time retarded by 9min and 21sec” – because half a globe away, the date line happened to go down the uninhabited Pacific and only needed to wiggle to avoid islands. That did not stop sovereign nations doing odd things with their own zones. China should, by the natural time of the sun (at its highest at noon) fall into five time zones, but insists on observing only one. So if you walk over the border to Afghanistan, your watch is three-and-a-half hours out.
If time zones are a political imposition – like making everyone get up an hour earlier by declaring summer time each year – discoveries such as the Wallace Line make sense of continental drift and biological evolution. Alfred Russel Wallace (1823-1913), who, like Darwin, was on the track of natural selection, found the fauna of the Indonesian island of Lombok utterly different from that of Bali, only 25 miles away. Bali had Asian creatures such as civets and woodpeckers; Lombok had Australian porcupines and white cockatoos. Unlike the straits separating other Indonesian islands, the waters between Lombok and Bali were too deep ever to have allowed a land-bridge when sea-levels fell. Evolution in either island had progressed without influence from the other.