The Domesticated Crops

Two general points about American plant domestication require emphasis. Firstly, some of the plants that were domesticated are non-staples in a food sense, for instance chilis, avocados, gourds, tobacco, and cotton. We can expect hunter-gatherers to have favored the growth of such useful plants and to have selected and planted seeds in some instances, as indeed they appear to have done with a species of squash (Cucurbita pepo) as early as 8000 uc in Oaxaca (Smith 1997b). The earliest use of teosinte / early maize might also have been for its sugary stalk, like sugar cane (Iltis 2000), and it is possible that primitive maize spread widely during the early Holocene as a source of sugar for alcoholic beverages, to be domesticated as a grain plant later and possibly in more than one location (Smalley and Blake 2003). Such initial movement as a snack food need have little directly to do with the origins of systematic agriculture, being more a case of occasional seed selection for replanting, in other words a variety of hunter-gatherer resource management.

Other plants, however, clearly served as staple foods, for instance maize in its eventual domesticated form in which the cob became the main exploited part, other seed-bearing plants such as chenopods (goosefoot in the Eastern Woodlands, quinoa in the Andes), various species of beans, and tubers such as potato, sweet potato, and manioc. Evidence for domestication of these staples generally falls much later in time than for the condiments and snack foods.

The second point is that a number of these plant species could have been domesticated in more than one region (Figure 8.1). Such possibilities have been raised for cotton, chilis, common and lima beans, some of the squashes, manioc, and even for maize.' Multiple domestications are quite possible for plants that have very widespread natural ranges, and we do not need to inflate the number of regions of independent agricultural genesis just because of this. But the situation as a whole does impart an air of diffuseness to the whole agricultural transition in the Americas. If there ever was an American "Fertile Crescent," tightly focused in space and time, it certainly hides from us very successfully.

Maize

Maize was the subsistence foundation for most late prehistoric and ethnographic American farming cultures, except for many groups living on poorer soils in Amazonia who depended mainly upon manioc and other tubers such as sweet potato (and bananas since European contact). Most botanists agree that maize was domesticated from one or more annual varieties of teosinte, the most important apparently being Zea mays var. parviglumis (Galinat 1985, 1995), which grows today in the Balsas river basin of Michoacan and Guerrero in western Mexico, with a closely related variety living slightly west in Jalisco, one of the possible homelands also for the common bean Phaseolus vulgaris. But the exact homeland of domesticated maize, as noted above, is a contentious issue.' The search goes on, as discussed earlier, and no firm conclusion can be offered here.

Throughout its history, maize has become perhaps the most widespread major food crop in the Americas, extending from 47°N to 43°S and up to about 4,000 meters in altitude. Its early spread into North America beyond the Southwest was not very rapid, perhaps because it is a short-day plant which had to adapt to the increasingly longer days and shorter duration of the summer growing season as it moved northward. Its entry into the southwestern USA occurred about 2000 BC, perhaps only a few centuries after large and productive varieties were first domesticated in Mexico (Matson 2003), but it did not spread into the eastern USA until about the time of Christ, only becoming a dietary mainstay there after AD 500. Maize clearly needed to evolve biologically, via human selection, as it spread.

In the early centuries of maize domestication it is possible that size increase was a slow process, owing to its wind-pollinated habit (as with the African millets), thus requiring conscious human planting in regions away from wild stands in order for improvements to become fixed (Iltis 2000). By 2000 ac, as noted by Kent Flannery (1972), maize had reached a size and level of productivity (cob length about 6 centimeters, yields perhaps 200/250 kilograms/hectare) that could have underpinned intensive production and the resulting Formative efflorescences of population in Mesoamerica, the Andes,

and the southwestern USA (Wilson 1985; Marcus and Flannery 1996:71).

Once in full production, maize clearly revolutionized American Indian life in many regions, certainly in Mesoamerica and the Southwest, even though it was preceded by other crops in the Andes and the eastern USA. Maize matures quickly, can be easily stored (an essential advantage), and has evolved many high-yielding varieties. One drawback is that it is lacking in available niacin, a problem remedied by cooking it in lime water in Mesoamerica and the Southwest, and pounding the kernels with wood ash in the eastern USA (Heiser 1990; niacin deficiency can cause pellagra).

When was maize domesticated? In Mexico, the oldest cobs of domesticated maize, as opposed to teosinte, come from ephemeral occupations in Guila Naquitz cave where the cobs themselves are dated by AMS radiocarbon to about 4250 BC (Piperno and Flannery 2001). Maize cobs from the Coxcatlan Phase layers in San Marcos Cave, in the Tehuacan Valley in Puebla, are AMS dated to about 3600 BC (Long et al. 1989; Benz and Iltis 1990). Carbon isotope analyses of human bone from a Coxcatlan phase burial in the Tehuacan Valley suggest increasing reliance on cereals by about 3500 BC, although this technique does not automatically identify the cereals as being domesticated (Farnsworth et al. 1985). However, Benz and Long (2000) note that maize cobs underwent rapid morphological development between 3500 and 3000 BC in the Tehuacan Valley sequence. Directly dated domesticated maize appears in northeastern Mexico and the Gulf lowlands of Tabasco by 2500 BC, and Zea pollen occurs with evidence for agricultural deforestation in the Maya lowlands at about the same time (Smith 1997a; Pope et al. 2001; Pohl et al. 1996).

There is a groundswell of opinion in favor of older dates for maize (see the discussion on stalk sugar above), especially for Middle and South America, where several locations in Panama and Ecuador have maize phytoliths or pollen in deposits dated by association to the early Holocene, back to at least 6000 ac (Piperno and Pearsall 1998; Pearsall 1999; Piperno et al. 2000). To the contrary, Bruce Smith (1995:159) accepts no dates for maize in South America until its clear presence in cob form after 2000 Bc at Valdivia in Ecuador, thus rejecting all older dates based on the finding of phytoliths in uncertain archaeological contexts. The debate on this continues, sometimes quite energetically. For instance, at the late Valdivia culture site of La Emerenciana, recent analyses of stable isotopes in human bone and phytoliths from dental calculus and food

residues in sherds indicate an increasing presence of maize, perhaps consumed in the form of chicha maize "beer," in the coastal Ecuadorian diet by 2200 sc. But maize cannot convincingly be demonstrated to have been present as a significant staple in South America before this date. Indeed, and rather ominously for the early dates scenario, maize is completely absent in several large agricultural sites of Late Preceramic date (ca. 2500-2000 BC) in northern Peru.'

The extent of the chronological problem for early maize, in this case in Panama, is highlighted by John Hoopes (1996:18):

Available models for both the introduction and the intensification of maize agriculture in western Panama ... are based on ambiguous evidence. Given various interpretations of both microbotanical and macrobotanical data, maize may have been introduced to the region anywhere between the sixth millennium B.C. and the early half of the first millennium A.D. Maize may have been: (1) modified indigenously from an ancient, primitive ancestor;

(2) introduced to the region from Costa Rica to the west; (3) brought from central Panama and Colombia to the east; or (4) introduced by some combination of these modes. Pollen and phytolith data indicate the presence of maize at inland rockshelters in central Panama ca. 5100 B.C ... However, the earliest macrobotanical remains from central Panama, in the form of maize kernels and cob fragments, date no earlier than 300 B.C. Hopefully, rigorous application of the principles of chronometric hygiene will soon help to sort out fundamental problems of this kind.