Superbugs from Hell - Evolution Re-Visited

Alvin's discovery turned out to be just the tip of the iceberg. In the 1980s, Thomas Gold, an astrophysicist from Cornell University, New York, supervised an oil drilling project in Sweden. On examining the rock cores from several miles down, Gold was amazed to find unmistakable signs of life.

At the time, the idea that something could live so deep in the Earth's crust was laughed at. There have been many stories about life in the underworld, from the Greek fable of Orpheus to Jules Verne's Journey to the Centre of the Earth. Few scientists took the possibility seriously. But Gold's claim was confirmed when other drilling projects yielded similar results. Biologists in the United States began extracting live microbes from miles beneath North Carolina and the Columbia River basin. Environmentalists became concerned that subterranean superbugs might eat through containment vessels of buried nuclear waste, causing leaks.

Meanwhile, the international Ocean Drilling Programme retrieved rocks from far below the seabed, and the story was the same. The basalt of the ocean floor is teeming with microbes too. Some of them have been cultured in the laboratory by John Parkes of the University of Bristol, who believes that some species can withstand temperatures as high as 169^oC. It is beginning to look as if there may be as much biomass inside the Earth as there is on the surface.

Our Ancestors?

The full significance of the deep-living microbes became clear only after their innards were analysed, following the pioneering work of Karl Stetter at the University of Regensburg in Germany. By sequencing the superbug's genes, microbiologists can construct a sort of family tree linking them with normal bacteria. The results came as a complete surprise. It turns out that the oldest and deepest branches of the tree of life are all occupied by heat-loving superbugs. In other words, the microbes residing deep within the Earth are among the world's oldest surviving organisms. In effect, they are living fossils, having changed little since the dawn of time.

Photo - Jerre Goldin Mono Lake in California is thick with salt and - in places - almost boiling. Yet it thrives with microbes, closely related to the earliest life-forms on Earth.

To some researchers these discoveries spell out a fascinating message. It suggests that life was incubated in the volcanic depths of the Earth, in pressure-cooker conditions, and migrated to the cooler surface zone only much later. This theory neatly meshes with what we know about the Earth's history. The Solar System is four and a half billion years old. For almost a billion years after the planets formed they were pounded mercilessly by giant asteroids and comets. A record of this primordial violence is etched on the face of our nearest neighbour in space - the Moon - which is pockmarked with countless large craters.