I have posted extensively on the huge pre-Columbian population of the
and particularly of the Amazon. They arose because they were able to master biochar production (mostly from maize stover and perhaps cassava waste) and thus maintain soil fertility. Americas
We do not know the actual population counts, but the potential with primitive maize culture was toward a hundred million. More reasonably the numbers possibly still peaked in the millions. These geoglyphs show the existence of large organized communities conforming to the proposition of millions of participants.
We know from early contact reports that the populations were more generally organized in villages and towns yet preserving large empty spaces between tribal neighbors. They preyed on each other for captives (cannibalism) which explained the need for separation. We do not know if this culture extended into the more organized agglomerations. I have never heard it been part of Incan culture though it was certainly adjacent to it and they did do human sacrifice at least.
We have plenty of reports that this population was extant at contact. We have blamed waves of killing pathogens for slashing these populations back. I have also pointed out that the advent of slash and burn (steel axe) may also have contributed mightily in allowing organized societies to disintegrate.
by Stephen Messenger, Porto Alegre, Brazil on 12.28.09
Because they are difficult to see from the ground, most geoglyphs went unnoticed by locals. Photo via Diego Gurgel
With the aid of satellite imagery from Google Earth, soon archeologists in
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. Brazil
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.
You do not see them in field. There is a difference in the color of grass but is very thin. If there were no satellite images, there would be no possibility [of making these new discoveries].
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.
According to a report from Globo, the new marks were only discovered because the jungle coverage had been removed to due to deforestation in the Amazon. 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?
The world may never know what drove these ancient civilizations to carve the enormous geoglyphs, like the ones found recently using Google Earth. But, if it takes more clear-cutting in the Amazon rainforest to find out the answer, hopefully it will always remain a mystery.