That's right, the Amazon flowed from the Atlantic Ocean to the Pacific, the opposite of its present direction. (1.)

Mapes worked on this together with his geology professor, Dr. Drew Coleman (University of North Carolina at Chapel Hill (2.)) and with Brazilian co-authors of the study Afonso Nogueira and Angela Maria Leguizamon Vega (Universidade Federal do Amazonas (3.)).

Crucial to the research was the presence of zircon fragments, the natural clock in which uranium decay reveals the age of the rocks.

As the researchers like to quip, zircon can help science find out about mountains that existed in the early ages and even about lost cities.

The geology is interesting and we will quote the findings, but first let us go over the images that instantly come to mind if you're one of those who believe that long, long ago, civilizations rose that we know very little or nothing about.

The first one must be that of ancient navigators using this waterway into and accross the Amazon region, from what we know today as Brazil's Marajó island delta, where the river flows out to the Atlantic.

Several routes into the early Americas have been considered, but not this one. Not going against the mighty Amazon River. Now that we know this giant was once western bound, many stories and legends about primeval South American cities, steeped in mistery, begin to look matter-of-course.

The rocks tell all

But, back to the rocks. Mapes explained that in the eastern side of the continent rocks may be as old as 2.5 billion years but those on the western side are much younger because of continual geological activity in the Andes. If the river had continuously flowed eastward, much younger mineral grains would have washed down from those mountains.

He further explained that the sediments of eastern origin came from a highland area that formed in the Cretaceous Period, "when the South American and African tectonic plates separated and passed each other. That highland tilted the river's flow westward, sending sediment as old as 2 billion years toward the center of the continent. A relatively low ridge - the Purus Arch, which still exists - rose in the middle of the continent, running north and south, dividing the Amazon's flow eastward toward the Atlantic and westward toward the Andes".

Near the end of the Cretaceous, he continues, "the Andes started growing, which sent the river back toward the Purus Arch.

Eventually, sediment from the mountains, with mineral grains younger than 500 million years old, filled in the basin between the mountains and the arch. After millions of years of build up", he concludes, "the Amazon finally broke through these sediments and flowed past the Purus arch into the eastern side of South America. This established the river's current course".

Adding to the excitement about these discoveries, this year a Brazilian expedition to the river's headwaters claimed to have established that the Amazon river is not only the largest river in the world, but the longest one as well at 6,800km (4,250 miles), compared to the Nile's 6,695km (4,160 miles). (5.)

The map shows results from NASA's Shuttle Radar Topography Mission (SRTM), used in 2000 to develop HydroSHEDS. The region identified as the Amazon's source (6.), is a network of riverbeds around snow-capped Mount Mismi, in southern Peru. (7.)

By 2001 it was verified that the main headwater of the Amazon River has its glacial source on Nevado Mismi. A National Geographic Society expedition discovered that "Carhuasanta, the longest of five headwater brooks flowing into Río Apurímac, originates on the northern slopes and then runs its course through other tributaries and rivers to help form the main Amazon River."

The fact was confirmed this year by the Brazilian team, pinpointing Quebrada Apacheta as the most probable source. Guido Gelli, director of science at the Brazilian Institute of Geography and Statistics said the expedition extended the Amazon's length by about 176 miles, making it 65 miles longer than the Nile. (8.)

Nevado Mismi is only a little over 99 miles west of Lake Titicaca and the ancient city of Tiwanaku. Here we have more food for thought if we wish to ponder on the ancestral concepts that thoroughly integrate the Andean world-view with the environment, with the Pachamama.

Of course, none of the above proves anything about exactly who was where and when. It does prove that if people were living in the region at the time when the Amazon changed its course, they must have faced truly fierce environmental challenges. Also, it stands out to reason that the answers researchers have been seeking, may be drawing near through geology. It is our good fortune that the rocks are still keeping the whole story for us.

Sandra Rodríguez-Beauchamp