London: Hundreds of geometric earthworks unearthed in the Amazon during clearing of forests could have been left behind by an earlier civilisation, archaeologists believe.
The excavations, that can be spotted against treeless, savanna-like landscape, raise questions on previous studies that claimed the area could only support small, impermanent villages, according to researchers.
More than 200 earthworks in various forms -- circle, square and triangle -- were recovered in 1999 from an area more than 150 miles across, covering northern Bolivia and Brazil's Amazonas state.
The earthen structures or 'geoglyphs' are made up of 30 ft wide and 10 ft deep ditches alongside 3 ft high walls. They are sculpted from the clay rich soils of Amazonia, as per the report filed by the researchers in the journal Antiquity.
Archeologists predict that nearly ten times as many earthworks exist undetected under the remaining forest.
Pointing out that at least 300 people would be needed to build such huge geoglyphs, co-author Denise Schaan from Federal University of Para in Brazil estimated the population
of the region to be around 60,000.
According to the report, most of these earthworks were situated on a 200m high plateau at the top of river valleys, giving inhabitants a defensive advantage with a clear view of
people coming up the river, Daily Mail reported.
Some hypothesise that geometric shape of the structures indicate that these monuments had ceremonial functions.
"Whether the sites were purely ceremonial or defensive, it is clear that the area was densely populated by relatively sedentary people at the eve of European contact," Schaan said.
Archeologists date one site to 1283 AD and are of the opinion that the others could be from as early as 200 AD. They believe that the civilisation was wiped out 500-years-ago due to diseases brought to South America by colonists.
PTI
First Published: Thursday, January 07, 2010, 10:29