FRIDAY JULY 20 2001
By Norman Hammond
from Mexico and Panama has shown that agriculture in the Americas
began around 7,000 years ago with the domestication of maize.
The process seems to have taken place in the lowland humid tropics,
not in the drier highland zone.
Spanish arrived in the New World, maize was the sole cereal
crop, a staple that supported village societies and civilisations
over the vast area of the United States to Chile. It was comparable
in its cultural importance to the wheat and barley which underpinned
the early civilisations of Mesopotamia and Egypt.
origins of maize, and hence its initial domestication by humans,
were thought to lie in Mexico. Forty years ago, the late Richard
Scotty MacNeish showed that maize was being grown
in the highland valley of Tehuacan at a date he estimated to
be around 5,500 BC, but recent radiocarbon dating of his finds
had brought that figure down by two millennia, to around 3,600
the Gulf Coast of Mexico, near the city of Villahermosa, from
the valley of Oaxaca to the Panama Canal, much further east,
all now suggest that MacNeishs date was close to the truth.
Farming also seems to have spread through tropical America well
before permanent villages were established, let alone the first
civilisations, with an informal network of communication which
would one day harden into trade routes for minerals and finished
On the Gulf
Coast, pollen evidence suggests that forest was being cleared
around 5,100 BC, and domesticated maize plants were being grown
only a century later, according to Kevin Pope and his colleagues.
Speaking at the Society for American Archaeology in New Orleans,
Dr Pope said that the San Andres site near the famous Olmec
centre of La Venta showed that maize had been introduced and
grown in a region of beaches and lagoons.
of fertile soils and easily harvested protein such as fish and
water birds made the area attractive, and evidence for the cultivation
of cassava (manioc), a carbohydrate- rich root crop, appeared
only a few centuries after the first maize. Cassava is thought
to have originated in the Amazon-Orinoco region of South America
and spread northwards to Mexico.
new radiocarbon dates from old excavations in the Valley of
Oaxaca, 160 miles to the southwest but several thousand feet
higher up, show that maize farming spread rapidly into the Mexican
highlands. Dolores Piperno and Kent Flannery report in the Proceedings
of the National Academy of Sciences that direct dating of corn-cobs
excavated by Flannery, at the cave of Guila Naquitz 30 years
ago, shows them to date to around 4,300 BC.
some 700 years older than the new dates for MacNeishs
early corn in the San Marcos and Coxcatlan Caves, at a still
higher altitude in the Tehuacan Valley, and suggests that farming
developed in the resource-rich tropical lowlands as part of
a mixed economy that included fishing, hunting and gathering.
Spreading to the highlands gradually as domesticated maize,
one of the most genetically plastic crops, adapted to higher
and drier climes.
of maize south-east to Panama and into South America, perhaps
along the same routes that took cassava northwest to Mexico,
has also been documented by Dr Piperno and her colleagues, by
identifying phytoliths, tiny opal crystals that form in the
cell tissue of plants, which enable species to be identified.
were identified in sediments at the Aguadulce rock shelter in
Panama, and both phytoliths and starch grains from maize were
recovered from grinding tools dating 5,000-3,000 BC. In a striking
piece of parallel research, maize phytoliths were recovered
from tartar deposits on the teeth of skeletons excavated at
the Vegas site, near Guayaquil in coastal Ecuador, hundreds
of miles to the south on the Pacific coast of South America.
the lines of direct, palaeobotanical evidence that can currently
be brought to bear indicate that maize was initially dispersed
out of Mexico into Central and South America between 5,200 and
3,000 BC, Dr Piperno and her colleagues conclude.