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from Montana show minute bodies similar in form and size to cells and cell-chains of existing [bacteria]. . . . These and similar contributions . . . are by no means convincing. . . . We can hardly expect to find in Pre-Cambrian rocks any actual proof of the existence of bacteria . . . ” (Seward, 1931, p. 92).

Seward's 1931 assessment of the science was mostly on the mark. Mistakes had been made. Mineralic, purely inorganic objects had been misinterpreted as fossil. Better and more evidence, carefully gathered and dispassionately considered, was much needed. But his dismissive rejection of Cryptozoon and his bold assertion that “we can hardly expect to find in Pre-Cambrian rocks any actual proof of the existence of bacteria” turned out to be misguided. Yet his influence was pervasive. It took another 30 years and a bit of serendipity to put the field back on track.

EMERGENCE OF A NEW FIELD OF SCIENCE

In the mid-1960s—a full century after Darwin broached the problem of the missing early fossil record—the hunt for early life began to stir, and in the following two decades the flood-gates would finally swing wide open. But this surge, too, had harbingers, now dating from the 1950s.

A Benchmark Discovery by an Unsung Hero

The worker who above all others set the course for modern studies of ancient life was Stanley A. Tyler (1906–1963) of the University of Wisconsin, the geologist who in 1953 discovered the now famous mid-Precambrian (2,100-million-year-old) microbial assemblage petrified in carbonaceous cherts of the Gunflint Formation of Ontario, Canada. A year later, together with Harvard paleobotanist Elso S. Barghoorn (1915–1984), Tyler published a short note announcing the discovery (Tyler and Barghoorn, 1954), a rather sketchy report that on the basis of study of petrographic thin sections documents that the fossils are indigenous to the deposit but fails to note either the exact provenance of the find or that the fossils are present within, and were actually the microbial builders of, large Cryptozoon-like stromatolites (an association that, once recognized, would prove key to the development of the field). Substantive, full-fledged reports would come later—although not until after Tyler's untimely death, an event that cheated him from receiving the great credit he deserved—but this initial short article on “the oldest structurally preserved organisms that clearly exhibit cellular differentiation and original carbon complexes which have yet been discovered in pre-Cambrian sediments” (Tyler and Barghoorn, 1954) was a benchmark, a monumental “first.”



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