One of the surprises that pre-Columbian history brought to later scholars is the slow development of the Peruvian highlands, the country’s political and economic core by the time the Spaniards showed up in the 16th century.

Such slowness is partly explained by the fact that proto-Inca populations were smaller until the genes needed to thrive at the high-altitude plateau (“puna”) and the custom of coca consumption became widespread enough. Another important reason is that the Peruvian Andes are huge in size and it took a long time before settlements reached a decent enough scale to evolve into cities with ceremonial centers and merchants bringing goods to their burgeoning populations.

Eventually, the region around Lake Titicaca, almost 4,000 meters above sea level, became the most densely populated in the highlands and in fact the only place in the planet where sustained agricultural production is possible at such an altitude.

This, however, was the result of even more adaptations, including terrace cultivation on the windy slopes around the lake itself, that were the result of gradual developments: the slopes are at huge altitude, but also very close to the equator, so they often get near-tropical temperatures in the daytime and effectively no seasonal variation because of strong solar irradiation (crops had to be adapted to survive frigid nights leading to frost, however).

There are an estimated 82,000 hectares of prehistoric ridged fields in the seasonally inundated land around Lake Titicaca.