Leaching of granitoids of the paleoproterozoic age was performed from several seconds to 360 days in water solutions (pH < 6.0) in the oxygen or argon medium. Under these conditions the entrance of K+ into the solution has been shown to occur at the higher rate than that of Na+. The obtained data are considered as evidence in favor of a possibility of the existence at the earlier stages of the Earth geologic history of water reservoirs with predominance of K+ over Na+. The K+/Na+ ratio exceeding 1 has been shown in prokaryotes, in cells and tissues of the free living and parasitic species of invertebrate and vertebrate animals. At the same time in the extracellular fluid of the fresh water, marine, and terrestrial animals, in which the Na+ concentration varies from 13 to 482 mmol/l, the K+/Na+ ratio is preserved at the level of 0.034 +/- 0.001. These results are discussed in connection with the problem of origin of protocells and of concentration ratios of monovalent cations in water phases of multicellular organisms.