First Farmers











The fish weirs join to form a funnel, the perfect location for a fish trap made of basketry or netting.
All photos this page
© Clark L. Erickson







Network of fish weirs and ponds from the air. Weirs are the dark lines, ponds the dark spots.













Pre-Columbian raised fields (lighter green) and canals (darker green) on the savanna in Bolivia. Raised fields allow farming on seasonally flooded areas. The canals provided soil and nutrients for the fields, water for irrigation and fish during the wet season.


Who, what, when, and weir?
To the average Sunday bait-drowner, fishing is fun. But to people who seldom see Safeway, fishing can make the difference between eating and starving. To these folks, worms and hand-tied flies are an unaffordable luxury.

If you're interested in sure-fire fishing, it's smarter to use a net -- or to channel the fish into a confined spot and trap them. These fish corrals, called fish weirs (rhymes with "beers"), have been used around the world as a low-technology substitute for the frozen-food section of the supermarket.

photo of fish weirNow comes a report that large tracts of the Amazon Basin were crafted into fish weirs. The finding is part of gathering evidence that Amazonia, once considered unsuitable for intensive human occupation, was extensively altered by substantial numbers of people.

Fresh fish finding
In a study just released in Nature, Clark Erickson, associate professor of anthropology at the University of Pennsylvania, describe short earthen dikes on about 500 square kilometers in Bolivia's Amazonian lowlands. Erickson says the fields were actually fish weirs, a key element of what he calls "landscape scale" food production technology (see "An Artificial..." in the bibliography).

Weirs and ponds are seen against a light field.The weirs were apparently built during the 1600s -- before the Spanish reached the area -- probably with simple technology like sharpened sticks or wooden spades. "They were built to be permanent, of earth, in an area where water flows so slowly that you don't have erosion," Erickson says. The lack of erosion explains why the weirs are still visible more than three centuries later.

Where did the builders get the idea? Erickson says that as floodwaters recede, some fish are naturally trapped in lakes and ponds. "People are observant... and think, why not make this system more effective?" The result was not only weirs, but also the ponds (seen in the photo) where live fish could be stored.

How much fried fish could a fishing fellow fetch from the fields that fascinate Erickson? In other words, how effective were the weirs? Erickson, a proponent of "experimental archeology," the reproduction and testing of ancient technology, says the issue remains to be studied.

Bands of dark and light green alternate in this airplane photo.However, he has examined raised beds, a related indigenous food-production technology that's used to grow crops that are sensitive to water or cold. In 1990, near Lake Titicaca, two miles above sea level in Peru, local people recreated the platforms, and, using organic fertilizers, compared them to standard farming approaches. "We got incredible production of sweet potatoes and manioc," says Erickson, although maize did not grow well.

Confused how a Why File on the birth of agriculture got sidetracked with weirs, which, because the fish are trapped, not raised, are not even fish farms? We figure they're a hybrid between hunting and farming. And if it's new, cool and related to our story, hey, it's fodder for The Why Files!

More thought for food -- or food for thought -- in our bibliography.


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