Abstract
Intracellular potassium concentrations, [K(+)], are high in all types of living cells, but the origins of this K(+) are unknown. The simplest hypothesis is that life emerged in an environment that was high in K(+). One such environment is the spaces between the sheets of the clay mineral mica. The best mica for life's origins is the black mica, biotite, because it has a high content of Mg(++) and because it has iron in various oxidation states. Life also has many of the characteristics of the environment between mica sheets, giving further support for the possibility that mica was the substrate on and within which life emerged. Here, a scenario for life's origins is presented, in which the necessary processes and components for life arise in niches between mica sheets; vesicle membranes encapsulate these processes and components; the resulting vesicles fuse, forming protocells; and eventually, all of the necessary components and processes are encapsulated within individual cells, some of which survive to seed the early Earth with life. This paper presents three new foci for the hypothesis of life's origins between mica sheets: (1) that potassium is essential for life's origins on Earth; (2) that biotite mica has advantages over muscovite mica; and (3) that micaceous clay is a better environment than isolated mica for life's origins.