Global health. The current scenario and future perspectives

97 probably like any other species. Ancestors of Homo sapiens only appeared in the Holocene, but before that, the planet underwent intense movements since its creation; microorganisms consumed gases and created an atmosphere viable for the rest of life. These microorganisms have diverse forms, such as microbial mats, biofilms, microbialites and stromatolites, which differ in their chemical composition and molecular structures (Rasuk et al., 2016). What they have in common is that they represent the oldest life records on Earth, about 3.5 billion years (Pérez et al., 2020, Rasuk et al., 2016). In Chile and Argentina, these microbial formations have been recorded in relic lagoons of Andean lakes, small saline lagoons of salt flats in the South American Puna (Chile and Argentina) (Demergasso et al., 2004, Farías et al., 2014; Pérez et al., 2020). They are also found in other parts of the planet like Mexico, Australia and the United States. Then the development of more complex life forms begins, including eukaryotes, multicellular organisms that require oxygen and food. This marks the dominance of these multicellular organisms, which create the large mammals and plants of the Jurassic and Cretaceous periods. Everything that has existed, exists and will exist on the planet is the result of a complex interaction between physical, chemical and biological processes. Up until this point, our ancestors managed quite well without Homo sapiens. As Darwin said, it is evident that over millions of years, the fittest individuals have persisted or evolved, those who can best adapt to changing conditions. Darwin’s theory opened new areas of knowledge in biological sciences and explained a well-kept secret. In his work “On the Origin of Species” (1859-1872), Darwin developed ideas to explain how species have modified and acquired different “forms and structures”, including the causes of variation between species and the variability within a species. Darwin references and reconstructs the relationship between geographical areas, glacial periods, the importance of seed dispersal and the unique characteristics of species that only inhabit oceanic islands. Silently, species activate their biological processes, a perfect machinery that adapts or dies with new local and global scenarios: volcanic eruptions, glaciations and meteorite impacts on Earth’s surface. There have been five major extinctions on the planet, with the most recent being the dinosaurs 65 million years ago (end of the Cretaceous period). According to some experts, we may be facing a sixth mass extinction of species. However, the cause driving this latest extinction has one single responsible party: humanity, which we will discuss further. We return to Darwin, who, to support his theory on species variability, argued that: “Variability is not actually caused by man; he only exposes (…) and then nature acts upon the organization and produces a variation. But