Interesting discoveries in the deforested Amazon

Treehugger (a Discovery Company Web site) has an interesting article about strange geoglyphs uncovered by the deforestation of the Amazon region.

With the aid of satellite imagery from Google Earth, soon archeologists in Brazil will be finding more and more large geometric designs carved into the ground in the Amazon rainforest. The geoglyphs are believed to have been sculpted by ancient people from the Amazon region around 700 years ago, though their purpose is still unknown. So far, nearly 300 geoglyphs have been identified, but with advances in satellite imaging--and increased clearing of the jungle coverage--scientists are hoping to discover many more of these strange, geometric designs.

One of the factors that contributed to so many geoglyphs being undetected prior to the aid of satallites is their enormous size. According to leading geoglyph scientist Alceu Ranzi, his latest discoveries--five sets of geometric shapes, with circles, squares and lines--can measure more than a mile from one extreme to another.

Geoglyph in a deforested area of the Amazon basin (photograph courtesy of Globo)

Because they've been so hard to find, the first geoglyphs weren't discovered until the 1970s. Since then, scientists have been trying to piece together what significance they may have had to ancient Amazonians. What ever the purpose may have been, there's one thing that is certain: the ancient civilizations of the rainforest were more numerous and sophisticated than previously imagined.

. . .

These structures are deep, with grooves are as large as 12 meters wide and four deep, but it is believed that they were built when jungle abounded--which would make their construction all the more difficult.

Ranzi seems open to other possibilities: "Was it really forest [when the drawings were built] or did they occupy this area at a time of climate crisis, like that of 2005?"

There's more at the link.

If these geoglyphs are, indeed, 700-odd years old, that would tie in with a period during which other great South American civilizations were flourishing. Are there links between them and the Mayan and Aztec cultures, to name but two? Was there another great civilization in that continent of which, until now, we've been unaware?

I'm particularly interested in Dr. Ranzi's postulation that the geoglyphs might have been made when the ground wasn't covered by forest. What was the situation in the Amazon basin seven hundred years ago? Was the forest as densely grown as today, or much more sparse? This might have a great deal of relevance, given the debate today about deforestation and how 'evil' this is. If, in fact, the forest wasn't always like it is today, will deforestation be as negative as it's claimed?

(Of course, the environmental lobby will fight any such suggestion tooth and claw, but it's a realistic one, and worth examining, I think.)

Peter