In the past, paleobiologists viewed the Precambrian as a long interval of time in which very little biological evolution occurred. Now however, now we recognize that this interval of geologic time was one of the most exciting in terms of biological change and innovation. The complete Precambrian record provides some of the best evidence for evolution through geologic time, beginning with the simplest, unicellular prokaryotic microorganisms and progressing through the earliest, unicellular eukaryotes into more complex colonial types, and finally, multicellular forms. Several authors have suggested that all the important biochemical and cellular evolution took place in the Precambrian and the various Phanerozoic life simply represents the morphological and physiological elaboration of forms that evolved in the Precambrian. The volume and importance of the work done in this area in the past 15-20 years is extraordinary. Perhaps nowhere else in the geologic record has such a diversity of evidence been applied to answer evolutionary questions, including biomarkers, geochronology, isotope chemistry, molecular phylogenetics of extant organisms, and microfossils. At this point in time, we are beginning to gain a clearer picture of the most ancient life—not just the types of organisms present, but also the environments in which they lived, their nutritional modes, and their interactions with each other and the abiotic world. As research on Precambrian life continues, one thing stands out, as it does in our modern world—the ubiquity and versatility of life on Earth.
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