Letter From Discover

Sunday, June 27, 2004

The Deep Chasm in Our Knowledge of Early Earth

There’s a constant theme that underlies much of what you read in Discover these days: Humans still don’t know very much. In our March issue, for example, you learned about the recent discovery that a third of all life on Earth lies below the seafloor, makes or eats methane, and dies in the presence of oxygen. How could we have previously failed to notice one-third of all the life on Earth? Soon after that issue came out, genomics guru Craig Venter surprised everyone when he announced that he had increased the known number of genes on Earth by 1.2 million, simply by sampling about 200 liters of seawater from four sites in the Sargasso Sea.

In the April issue you read that we know little about Mercury and that it may contain more clues about extraterrestrial life than Mars does. In this issue you’ll discover that we don’t know much about gravity, or how one of the most-studied animals on Earth—the dog—evolved, or what life will be like when we run out of oil. Most important, you’ll find out how little we know about early life on Earth.

Earth is unique among planets in our solar system; it’s the only one that’s solid and active. By active, scientists mean that Earth’s surface is constantly changing. Volcanic action forces new material from inside the planet, while tectonic action and other geologic forces fold surface material beneath the crust. That makes it difficult to uncover evidence of Earth’s early history and how life formed here. We can’t find rocks, and thus geologic or fossil records, that are as old as Earth because they’re no longer on the surface. And talk about not knowing much—we don’t even know what’s below our feet. The distance from the surface to the center of the planet is 4,000 miles, but the deepest that humans have ever penetrated is a mere 7.5 miles.

Even though we know so little about the early Earth, laboratory scientists may soon re-create some of the earliest life that emerged out of the primordial muck, life that no longer exists. The subject of this month’s cover story is an attempt to create a one-celled organism so primitive that it preceded DNA. How ironic that while our knowledge is good enough to sequence more than a million previously unknown genes in a matter of months and even re-create life that no longer exists, we have no real knowledge about the material that makes up nearly all of the sphere we live on.

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