This article was originally posted on RealClearScience.

Biologists have categorized life into three large domains: Bacteria, Archaea (weird, bacteria-like microbes), and Eukarya (unicellular and multicellular organisms such as fungi, plants, and animals that possess nucleated cells). Under this classification system, viruses are left out in the cold. They certainly are not “alive” in the classical sense because they are not capable of metabolizing or replicating on their own. But it does not feel quite right to classify them as “inanimate,” either, because they are built of biological molecules and contain genetic information. Thus, for the most part, viruses languish in the no man’s land between the living and the dead. Continue reading →