Although the jury is still out regarding the origin of SARS-CoV-2, it is most likely to have originated in an animal reservoir. Whilst a new variant is rapidly sweeping across human populations, incidents of transmission in the reverse direction (to other mammals) are increasingly being reported.
Looking at Longman, J. et al.'s journal paper, this article analyzes the connection between Late Ordovician marine productivity and cooling episodes to subaerial volcanic activity.