Earliest Life

Life on earth began more than 2 billion years ago, but only in a few places are primitive fossils clear enough to give paleontologists any faint clue to what that life was like. Most rocks that date from those early years have been deeply buried for so long and subjected to so much heat and pressure that all organic traces they once contained have been turned to shapeless specks of carbon. One notable exception is a hard, black, ancient rock found near Gunflint Lake in western Ontario, which somehow escaped this rough treatment. In the magazine Science, Paleontologist Elso S. Barg-hoorn-of Harvard and the late Geologist Stanley A. Tyler of the University of Wisconsin describe the remains of microscopic organisms that lived in that "Gunflint chert" -- an impure silica --about 2 billion years ago, 1,800 million years before the earliest dinosaurs.

Dim Stirring. From those tiny things, the two men boldly re-created a vast era of prehistory. In that remote period, they say, the region that is now the northwest shore of Lake Superior was covered by a shallow sea or perhaps a chain of lakes. The dry land was devoid of life; the atmosphere may have been unbreathable for most mod ern creatures. But in shallow pools, say the paleontologists, a dim kind of life was stirring. The bottom was covered with hard hummocks -- mounds made of tight-packed vertical columns, a fraction of an inch in diameter, that were created by living matter.

The living parts were on the tips: microscopic threads of algae tangled together, busily depositing silica that stiffened the columns. The hummocks eventually became the Gunflint chert, which radioactive dating proves to be 2 billion years old.

Drs. Barghoorn and Tyler selected 800 promising samples and ground them to paper thinness. Studied under a microscope, they showed a great variety of organisms. Few of them resemble anything that still lives today, and their discoverers gave them such fanciful scientific names as Eoastrion (little dawn star), Kakabekia (after a waterfall in Ontario) and Eosphaera (dawn sphere).

The water above the hummocks must have teemed with tiny boating things that sank between the silica columns when they died. Those things may have been plants or animals or something in between. Whatever they were, they resembled small stars, or spheres with smaller spheres sticking to their outside walls. The most elaborate form had a bulbous base, a stalk and a ribbed cap. Its discoverers do not know whether it was sedentary like a mushroom or swam like a miniature jellyfish.

Ancient Atmosphere. By analyzing organic matter extracted from Gunflint chert, Dr. Barghoorn got some idea of how the primitive organisms lived. The carbon in them contains a relatively small proportion of carbon 13 (a rare, stable isotope of carbon), showing that it was probably extracted by photosynthesis from carbon dioxide in the air. Modern plants grow in this manner, but Professor Barghoorn is not sure that earth had its present atmosphere that long ago. The Gunflint chert also contains minerals, such as pyrite (iron sulphide), that are deposited from solutions containing no oxygen. He suspects that these minerals may have been deposited while the earth's atmosphere was in a transition state, just beginning to accumulate the oxygen that was being released by the photosyntheses of slow-living, primitive plants.

* Brother of Yale's Frederick C. Barghoorn, professor of political science, who was jailed briefly in Russia in 1963 on trumped-up spy charges.

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