The possible role of Ca2+ as a promoter of the major steps in the evolution of early life is reviewed. The existing biological
knowledge about the role of calcium in living systems is summarized and compared with the major bio-evolutionary events that occurred
during the first three billion years of Earth’s history. It is proposed that secular changes in Ca2+ concentration in the marine realm during
the Precambrian were the crucial driving force behind major innovations in the evolution of early life, such as photosynthesis, eukaryogenesis,
multicellularity, origin of metazoans, biocalcification and skeletogenesis.
Keywords: Photosynthesis, Eukaryogenesis, multicellularity, Origin of metazoans, Biocalcification, Skeletogenesis, Evolution of early life,
Calcium, Alkalinity, Early alkaline ocean.
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