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.For example, reservoirs at the Maya city of Tikal held enoughwater to meet the drinking water needs of about 10,000 people for a periodof 18 months.At the city of Coba the Maya built dikes around a lake in or-der to raise its level and make their water supply more reliable.But the in-habitants of Tikal and other cities dependent on reservoirs for drinkingwater would still have been in deep trouble if 18 months passed withoutrain in a prolonged drought.A shorter drought in which they exhaustedtheir stored food supplies might already have gotten them in deep troublethrough starvation, because growing crops required rain rather thanreservoirs.Of particular importance for our purposes are the details of Maya agricul-ture, which was based on crops domesticated in Mexico especially corn,with beans being second in importance.For the elite as well as commoners,corn constituted at least 70% of the Maya diet, as deduced from isotopeanalyses of ancient Maya skeletons.Their sole domestic animals were thedog, turkey, Muscovy duck, and a stingless bee yielding honey, while theirmost important wild meat source was deer that they hunted, plus fish atsome sites.However, the few animal bones at Maya archaeological sites sug-gest that the quantity of meat available to the Maya was low.Venison wasmainly a luxury food for the elite.It was formerly believed that Maya farming was based on slash-and-burn agriculture (so-called swidden agriculture) in which forest is clearedand burned, crops are grown in the resulting field for a year or a few yearsuntil the soil is exhausted, and then the field is abandoned for a long fallowperiod of 15 or 20 years until regrowth of wild vegetation restores fertilityto the soil.Because most of the landscape under a swidden agricultural sys-tem is fallow at any given time, it can support only modest population den-sities.Thus, it was a surprise for archaeologists to discover that ancientMaya population densities, estimated from numbers of stone foundationsof farmhouses, were often far higher than what swidden agriculture couldsupport.The actual values are the subject of much dispute and evidentlyvaried among areas, but frequently cited estimates reach 250 to 750, possi-bly even 1,500, people per square mile.(For comparison, even today the twomost densely populated countries in Africa, Rwanda and Burundi, havepopulation densities of only about 750 and 540 people per square mile, re-spectively.) Hence the ancient Maya must have had some means of increas-ing agricultural production beyond what was possible through swiddenalone.Many Maya areas do show remains of agricultural structures designed toincrease production, such as terracing of hill slopes to retain soil and mois-ture, irrigation systems, and arrays of canals and drained or raised fields.The latter systems, which are well attested elsewhere in the world and whichrequire a lot of labor to construct, but which reward the labor with in-creased food production, involve digging canals to drain a waterlogged area,fertilizing and raising the level of the fields between the canals by dump-ing muck and water hyacinths dredged out of canals onto the fields, andthereby keeping the fields themselves from being inundated.Besides har-vesting crops grown over the fields, farmers with raised fields also "grow"wild fish and turtles in the canals (actually, let them grow themselves) as anadditional food source.However, other Maya areas, such as the well-studiedcities of Copan and Tikal, show little archaeological evidence of terracing,irrigation, or raised- or drained-field systems.Instead, their inhabitantsmust have used archaeologically invisible means to increase food produc-tion, by mulching, floodwater farming, shortening the time that a field isleft fallow, and tilling the soil to restore soil fertility, or in the extreme omit-ting the fallow period entirely and growing crops every year, or in especiallymoist areas growing two crops per year [ Pobierz całość w formacie PDF ]