Our knowledge of the fossil record has changed immensely since 1859, when Darwin felt obliged to explain why his hypothesis of gradualism was not confirmed by the study of fossil successions. His argument was, as is well known, that the fossil record exhibits extreme imperfection. The abrupt appearance of macrofossils at the base of the Cambrian was recognized and Darwin deduced that the evolutionary origins of those animals must have extended well back into the Precambrian.
“One-and-a-half centuries of subsequent research have revealed a vast microscopic fossil record of unicellular protists and bacteria extending, some would argue, as far back as there are sedimentary rocks from which they could be recovered. But although fossils of millimetre- to metre-scale multicellular organisms characterize the 90 million years of the Ediacaran period that precedes the Cambrian, pre-Ediacaran macroscopic fossils are exceedingly rare.”
Over the years, various attempts have been made to vindicate Darwin’s approach. The Ediacaran fauna shows that soft-bodied animals were preserved in the Precambrian, even in coarse sandstone beds, suggesting that fossils are not found because they were not there. In any case, there is no gradualist understanding of the Ediacaran fauna or any gradualist connection with the fossils of the “Cambrian Explosion”. Prior to this, there is a unicellular fossil record with very few suggestions of macroscopic fossils. The newly reported finds are from sediments dated at 2.1 billion years old. They are interpreted by the researchers “as highly organized and spatially discrete populations of colonial organisms” with growth patterns “commonly associated with multicellular organization”. If correct, this makes them the earliest known multicellular life.
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