Arsenic and Its Biological Role: From Early Earth to Current Andean Microbial Ecosystems

While it is true that the chemistry of current life is well defined, 3.5 billion years ago, everything could have been different. Other elements may have been part of the chemical reactions that finally triggered an endless iteration with well-defined laws that gave way—and continue to give way—to the evolution of life. In this sense, arsenic could have been a key element for life back then. Its high reactivity and its abundance in the context of a reduced atmosphere could have given this element a key role, whereas nowadays it is so alien to the development of life. In this chapter, we address this question with a special emphasis on the description of one of the best natural laboratories to study early life that our planet presents: the Andean Puna.