One of the most baroque examples of parasitic behavioral control involves so-called zombie ants. Certain species of ants have the misfortune of being prone to infection by a particular species of fungus (Ophiocordyceps unilateralis); the fungus prompts them to climb a plant to certain height and then bite into a vein on the underside of a leaf in a death grip. The fungus then kills the ant and grows a large mushroom-type stalk from the ant’s head from which its spores can rain down on future ants. This phenomenon was first observed by Alfred Russel Wallace, a naturalist who advanced a theory of natural selection at the same time as Darwin but who received much less recognition for his efforts. Here, we have an example of a species without a nervous system (the fungus) evolving to control the behavior of the species with a nervous system (the ant), converting the latter into a spore-delivery platform. We know from fossilized leaves showing telltale marks of ant bites on their veins that this fungal phenotype is tens of millions of years old. it possible that some human traits and behaviors may actually be the genetic by-product of other organisms’ genes?

Is it possible that humans sneeze not to expel pathogens from the upper airway for our own benefit, as I was taught in medical school, but for the benefit of the pathogens that might thereby spread through the air? Maybe our behavior is being manipulated by those very pathogens. Humans think that sneezing is something that we do to the germs to clear those pesky invaders from our bodies and promote our own well-being. But maybe it is something the germs do to us to help facilitate their own spread and increase their fitness. Some intestinal worms may decrease human fecundity in the furtherance of their own interests. Maybe, when people are infected with certain pathogens, they behave in ways that prompt their loved ones to come close and take care of them (manipulating the human tendency to love, befriend, and cooperate), which in turn facilitates the further spread of the pathogen that made them sick. It might not be a coincidence that people who are sick act like babies, eliciting help from caregivers.

Some scientists have even proposed the highly speculative hypothesis that microorganisms could increase their evolutionary fitness by encouraging certain aspects of human religious behavior that flesh, favor rolling their transmission, on the ground, acts or such as mortification of holy the relic by large numbers of people kissing of an icon thus or might facilitating even enhance our while desire also to form aggregations, Microorganisms might even enhance our desire to form aggregations, thus facilitating their spread while also shaping our social lives.

A passage from Blueprint by Nicholas A. Christakis


Currently reading Guns, Germs and Steel by Jared Diamond

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