About 500 years ago a group of Incas marched hundreds of miles through the treacherous Andes Mountains to the top of a distant volcano, where they buried three children alive as part of a religious ceremony. In 1999, an expedition led by explorer Johan Reinhard unearthed the mummies atop Argentina's Mount Llullaillaco (yoo-yay-YAH-co), finding that they were among the best preserved mummies ever discovered, with largely unscathed skin and facial features.

When University of Colorado researcher Steve Schmidt read about the mummies, he knew he had to visit the region — not to see the mummies, but to study microbes. Normally, bodies that old would have long ago decayed, in part by the action of microbes, so Schmidt reasoned that the microbes on the mountain, if there were any, must be pretty intriguing.

"Finding a body so well-preserved 500 years after burial, without preservatives — that's remarkable," Schmidt told OurAmazingPlanet. "That's the reason I first got interested in the mountain."

So his team traveled to the area, climbed the volcano and took samples of soil near the summit. After performing genetic tests on the microbes, his group found several unique varieties that have not been described before. The most abundant were from a subset of Actinobacteria, the group that has given rise to most human antibiotics. They also came from 12 different broad groups called phyla, and all three domains of life.

And yet, the lack of diversity was what most surprised Schmidt. "We've studied many other soils around the world, and this is by far the simplest system we've seen," Schmidt said. Per gram, soil in your garden likely has hundreds or thousands more varieties of microbes than the stuff atop Llullaillaco, he said. "That speaks to the fact that it's such a harsh environment."

This ecosystem of fungi and bacteria is the highest ever studied on land, Schmidt said. That's fitting, perhaps, as it's found next to the highest archaeological site on the globe.

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