THE LINEAGE OF MAN
earth’s crust, the older sedimentary rocks were soaked and honeycombed with the molten rock coming from below and were squeezed, mashed, folded, contorted, baked, and partly melted, so that if they ever contained any traces of life, such traces would have been hopelessly obliterated, the only possible signs of organic life being the beds of graphite occasionally found in the oldest known rock formations.
Such is the picture suggested to the geologist by the study of the oldest known rocks, now exposed again in eastern Canada, the Lake Superior region, and the Adirondacks as a result of hundreds of millions of years of erosion, but in former ages lying as the “basement complex,” beneath tens of thousands of feet of later rocks.
Passing over various doubtful traces of living organisms in the oldest sedimentary rocks (such as the famous “Eozoön canadense,” which may be a mineral formation), we come to certain markings occurring in the Proterozoic limestone formations, which were determined by the great palaeontologist C. D. Walcott as the calcareous secretions of algae. In the upper levels of the “Belt series” of formations in Montana; exposed on the side of a mountain and lying nearly eight thousand feet below the Cambrian, or lower part of the Palaeozoic, Walcott found the fossilized traces of worm burrows and trails, seemingly of segmented annelid worms.
Hence even far below the bottom of the Palaeozoic system, which to the earlier geologists marked the utmost lower limits of the record of fossil life, we come upon animals of marvelous complexity compared to their one-celled starting point. But where the fossil record fails, the “chain of beings” still in existence apparently preserves some of the main steps in the elaboration of higher living types out of single living cells. For even to-day there are forms of life that afford strong evidence for the following outline.
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