Bacteria can distinguish “self” from “other,” and between their relatives and strangers. They can communicate, prey in packs, and have social intelligence. Are microbes far more sentient than we give them credit for? Miller-McCune writes:
Strictly by the numbers, the vast majority — estimated by many scientists at 90 percent — of the cells in what you think of as your body are actually bacteria, not human cells. In fact, most of the life on the planet is probably composed of bacteria.
These facts by themselves may trigger existential shock: People are partly made of pond scum. But beyond that psychic trauma, a new and astonishing vista unfolds. In a series of recent findings, researchers describe bacteria that communicate in sophisticated ways, take concerted action, influence human physiology, alter human thinking and work together to bioengineer the environment. These findings may foreshadow new medical procedures that encourage bacterial participation in human health. They clearly set out a new understanding of the way in which life has developed on Earth to date, and of the power microbes have to regulate both the global environment and the internal environment of the human beings they inhabit and influence so profoundly.
Bacteria use chemicals to talk to each other and to nonbacterial cells as well. These exchanges work much as human language does, says Herbert Levine of the University of California, San Diego’s Center for Theoretical Biological Physics. With colleagues from Tel Aviv University, Levine proposed in the August 2004 Trends in Microbiology that bacteria “maintain linguistic communication,” enabling them to engage in intentional behavior both singly and in groups. In other words, they have “social intelligence.”