BASIC BOOKS, January 2014If you get stranded up there, whatever you do, don’t try to climb down. That’s basic advice for biologists working on the summits of tepuis, the isolated, table-top mountains that dot the savanna of southern Venezuela and nearby parts of Brazil, Colombia, Guyana, and Suriname. Tepuis—“houses of the gods” in the language of the local Pemón Indians—are the monolithic remnants of a sandstone plateau that formed well over a billion years ago, long before the breakup of Gondwana or the formation of Pangea. Much more recently, over the past 70 million years, wind and water have been grinding down the plateau, with only those parts that were capped with more resistant rock remaining as these towering flat-topped mountains, their standstone cliffs now rising thousands of feet above the surrounding country. On the tops of the tepuis are misty, dripping landscapes of dwarf forests; streams running through pink sand; rock formations eroded into weird convolutions; and fields of plants with naked stalks and tufted heads, like something out of Dr. Seuss. “Otherworldly” is a word that crops up often in descriptions of these places. Adventurous tourists and scientists can get dropped off by helicopter onto tepui summits, but, not uncommonly, clouds or fog will prevent the scheduled pickup. At that point, the thing to do is wait, even if the delay drags on for days, because trying to find a way down the cliffs is likely to get you lost, or stuck halfway down, or inadvertently airborne.
The otherworldliness and inaccessibility of tepuis are exactly what draws biologists to them. Those cliffs that keep people from climbing up or down are also a barrier for other living things and, to many biologists, this has implied that the organisms living on the tops of the tepuis have been evolving in prolonged isolation, perhaps for many millions of years. This idea of tepuis as areas populated by relicts took root in the Western world in the 1860s, before Europeans had even climbed them. In the early 1900s, when Arthur Conan Doyle wrote The Lost World, famously imagining a tepui filled with dinosaurs, pterodactyls, ape-men, and other prehistoric creatures, he wasn’t inventing a view of tepui biotas so much as taking the accepted notion to ...
