You’d think we’d learn. The ocean is 350 million cubic miles of water covering 140 million square miles of seafloor mud and rock, almost all of which no human has ever laid eyes on. You’d think we’d learn to expect the unexpected. But it seems to be human nature to underestimate the unknown. We think we know more than we do; we think we’re on the edge of knowing it all. It has happened again and again in our study of the sea.
Pliny the Elder surveyed his patch of the Mediterranean in the first century A.D., found 176 types of animals—and decided that was it for the whole ocean. Edward Forbes, the British naturalist, launched deep-sea biology in the 1830s, dredging to a depth of 230 fathoms in the Aegean—and decided that below 300 fathoms, or 1,800 feet, there was probably nothing alive in the whole ocean. It wasn’t until 1952 that the last remnants of this “azoic zone” myth were laid to rest by a Danish expedition. The scientists on the Galathea dredged living mollusks, worms, and sea cucumbers from 33,600 feet in the Philippine Trench, one of the deepest spots in the ocean.
One of those scientists was a pioneering American microbiologist named Claude ZoBell, of the Scripps Institution of Oceanography. ZoBell showed that there were microbes living in the Philippine Trench, and everywhere else he looked on the seafloor, and that they had adapted to the fantastic pressures there. He believed that microbes played an important role in oil formation and in other geologic processes. And yet ZoBell announced in 1955 that he had finally found the real lower limit of the biosphere and the beginning of a new azoic zone—the microbes stopped about 25 feet or so below the seafloor. As our cover story this month shows, he was quite wrong: Life extends to a depth of at least half a mile below the seafloor. And researchers have suddenly realized that those deep microbes may have a big effect on the rest of Earth.
All too often, imagination fails the best of us. One exceptional biologist, J. B. S. Haldane, expressed it pithily: “The universe is not only queerer than we suppose, but queerer than we can suppose. . . . I suspect that there are more things in heaven and earth than are dreamed of, in any philosophy.”
And that’s a good philosophy for a science magazine.