Microorganisms (including viruses) have shaped the evolution of all living creatures since the beginning of life on Earth 3.8 billion years ago. They still put pressure on all living organisms. Because life is symbiotic (i.e., all life depends on other lives), the initial primitive border protection of single cells had to be developed against transgressive microorganisms. Thus, all organisms needed to discriminate self from non-self. With time, this simple recognition system developed into highly complex immunological mechanisms. In the symbiotic relationship, all animals take in and feed trillions of microorganisms in their body, mainly in the gut, to help digest food but also to train their immune system. We need to understand that microorganisms are neither our enemies nor friends. Survival of all life forms depends on maintaining a delicate balance between self and non-self, i.e., microorganisms. Understanding the symbiotic nature of life on Earth might help prevent further destruction of nature.

Keywords: