Tracking the History of Early Life on Earth

September 19, 2016

Back in the 19th century, Charles Darwin wondered why he could find no fossil evidence of life that predated the Cambrian Period, 541–485.4 million years ago. He understood that life must have evolved in complexity over millions of years, yet the fossils that appeared at the beginning of the Cambrian Period were surprisingly advanced: macroscopic, multicellular, and diverse in form.

About a hundred years later, in 1953, fossilized microorganisms from a much older period (about 1.9 billion years ago) were finally found in the Gunflint chert on the Canadian shores of Lake Superior, giving scientists a much better picture of how the earliest life evolved. This pre-Cambrian fossil record charts the emergence and diversification of one-celled organisms, the advent of multicellularity and sexual reproduction, and the evolution of macroscopic organisms.

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