The viruses may be the missing link in the evaluation of life. Formation of Earth’s oldest ecosystems, stromatolites, requires a deeper understanding of several virus-mediated mechanisms that change the cyanobacterial behavior through geologic time, including the “invention” of oxygen-producing photosynthesis. Cyanobacteria also precipitate and cement the carbonate minerals, a stromatolite is preserved in the fossil record, some for as long as 3,500 million years. Without the interception of viruses, this may not have happened and further evolution of life and biogeochemistry that resulted in the Cambrian explosion would have been different. A planet without humans….?

https://today.uconn.edu/2021/02/lifes-surprising-debt-to-viruses/

Mechanisms proposed for virus-cyanobacteria interaction. Image: Richard White III