Thursday, October 26, 2006

Footprints in the valley
The Cuatro Ciénegas Valley is a biological wonder hidden in the Eastern Sierra Madre Mountains of Mexico. The Nature Conservancy, which is working with Mexican groups to preserve as much of the region as possible, describes it as:
As a rare sanctuary in a harsh desert habitat, Cuatro Ciénegas teems with endemic species. The refuge has more than 75 species of fish, reptiles, amphibians, crustaceans, mollusks, insects and more than 400 species of cactus found nowhere else in the world. An impressive variety of bats and migratory birds also find refuge in this desert oasis. The gypsum dunes, native grassland matrix community, xerophilic shrubs, canyon systems, and Coahuilan box turtle are other targets that have been the focus of attention in Cuatro Ciénegas.

Cuatro Ciénegas is more than a unique environmental heritage; it is also an important scientific laboratory. NASA's attention has been drawn to the region by primative algae and bacteria growing in some of the pools. Because the stromatolite-forming algae resemble the earliest life known to have existed on Earth, NASA believes studying the ecosystem of the pools can give them clues on how to identify life on other planets. The NASA research team at Cuatro Ciénegas is focusing on identify the type of atmosphere being produced by the primitive life forms. When the next generation of orbiting telescopes replace Hubble in the next decade, data from Cuatro Ciénegas will guide the research programs to study the atmospheres of planets around other stars. If we discover other life in space, this is the most likely way we will find the first traces. Other research teams are looking into the evolution of cynobacteria and horizontal gene transfers.

Now we can add archaeology to Cuatro Ciénegas' treasures. A joint Mexican-American team thinks they may have located the oldest human footprints in the new world in the soil around one of the springs. In 1961 Arturo Gonzalez, director of the Museo del Desierto in Saltillo, Mexico, found casts of two human footprints in a small museum and has spent the last forty-five years trying to find out where they were from. Last May, he and Martin Lockley, director of the Dinosaur Tracks Museum at the University of Colorado, discovered the source. The two footprints were part of a track thirteen prints and almost thirty feet long.

Though tests are still being run, based on stratiography, the two think the prints are ten to fifteen thousand years old. This easily makes them the oldest in North America--six thousand year old prints have been identified in Nicaragua and California--and possibly the oldest in the new world. A single footprint at Monte Verde in Chile has been dated at 12.5 thousand years old.

At the end of the last ice age, Cuatro Ciénegas would have been an even richer environment than it is now. It's marshes would have been filled with migratory birds, its pools with edible shellfish, and its surrounding land would have teemed with game drawn by the grasses and springs. For any humans who had crossed the dry mountains surrounding the valley, this would have been a paradise. As the mountains became even dryer following the ice age, the valley would have become even more attractive. Gonzalez and Lockley's discovery will help us better understand the lifestyle of some of the first people in the Americas.

Until very recently, most archeologists believed that the first humans entered North America overland into the central plains about 11.5 thousand years ago. These people are called the Clovis culture. Pre-Clovis finds, like Monte Verde, remain controversial, but are becoming more broadly accepted. However, assembling the scattered pre-Clovis finds into a coherent history still escapes the archaeological community. Cuatro Ciénegas might be one more valuable piece in the puzzle.

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