Calcium in the Early Evolution of Living Systems: A Biohistorical Approach

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.