Viruses and bacteria are generally called microorganisms. The disaster of viruses and bacteria is the biggest one encountered by living creatures. It not only has left a serious disaster in the history of human society but also has been an important promoter of the mass extinction in the history of the evolution of the Earth's life. Although it is difficult for viruses and bacteria to form solid fossils, a special molecular fossil has become a magic needle for the detection of biological extinction in geological times. With earth microbiology as the guide and cyanobacteria and green sulfur bacteria molecular fossils as the study case, the authors comprehensively explained relevant research results and interpreted the relevant knowledge of microbiology, viruses and bacteria, and microbial rocks, thus helping people understand the two most important events of mass extinction in the history of the earth's biological evolution. This paper also clarifies the association relationship between human and fungus based on the enlightenment from the agricultural revolution in the process of human evolution.