The Incas of South America knew nothing about wheels. Well, maybe they did, but just never bothered to use them as an aid to transportation. In any event they did very well without them, and by the early 1500s, just before the Spanish rudely intervened, the Inca Empire extended over most of modern Peru and Ecuador, parts of Chile and of Argentina and large tracts of what is now Bolivia.
Incadom, if I may call it that, was highly centralised and was ruled by a single dynastic family possessing practically absolute power but apparently of largely benevolent intent. Its people were skilled engineers and road makers and were well versed in the principles of irrigation. They also had an interesting technique for long-range weather forecasting - one which meteorologists nowadays believe may have had a solid basis.
At the end of June each year, it seems, Inca farmers would climb high into the Andes and observe the stars. They had a particular affection for the Pleiades, or the Seven Sisters - a galactic cluster in the constellation Taurus comprising an association of some half a dozen stars visible to the normal naked eye, and of many more if the observer's sight is good enough.
If the Pleiades were crisp and clear against the night sky, it indicated normal rainfall for the approaching growing season from October until May and a good harvest early in the following year. If the stars appeared indistinct and fuzzy, it was a sign of late and meagre rainfall and perhaps a drought; the Incas would delay the sowing of their crops for several weeks in the hope of at least a modicum of moisture, even if a little late.
It is now suggested that this belief may be related to El Nino. During the periodic El Nino episodes, when the surface waters of the tropical Pacific may be several degrees warmer than they usually are, global rainfall patterns tend to be distorted. In particular, El Nino conditions often result in a hot, dry growing season in many parts of Peru and Ecuador, with the potato crop severely stunted or maybe even lost. Also linked to an El Nino event is a significant increase in the amount of high cirrus cloud over the region. It is suggested that this may have been what made the Pleiades occasionally fuzzy, indicating the occurrence of an El Nino event and therefore problems with the coming harvest.
Be that as it may, it is said that in South America some local farmers still climb high into the mountains every June to observe the stars and get their long-range forecast.