Magazine article Psychology Today

The Domesticated Human

Magazine article Psychology Today

The Domesticated Human

Article excerpt

WE LOVE A well-behaved dog. Amiable and docile, he knows how to W sit, play dead, and roll over-all on demand. His good-natured manner comes with traits like a short snout, a small jaw, and even reduced levels of fight-or-flight stress hormones-all of which characterize animals that have been domesticated by humans. The last thing you want is a pet that tears off the neighbor's arm.

Though we don't think of it this way, humans are just as domesticated. We have made our own species conform to itself-the more cooperative and sensitive to others, the better. We prefer tame children to wild ones. And while all human populations vary around a mean, most will be proportionately domesticated-just as most people will be near average height, with a few short and a few tall. Likewise, the underdomesticated and the overdomesticated are outliers from the mean.

Domesticated traits of modern humans include reduced brain size over the last 50,000 years, changes in dental structure, and reduced aggressiveness. But, argues Antonio Benitez-Burraco, of the University of Huelva in Spain, and Wanda Lattanzi, of the Catholic University of the Sacred Heart in Italy, these traits are absent or minimal in people with autism; and genes believed to be important for the self-domestication of our species, as well as the evolution of cognitive abilities, most notably language, are atypical in the brains of autistics, the underdomesticated.

In autistics, the hypothalamicpituitary-adrenal axis, which is responsible for fight-or-flight behaviors, responds abnormally, leading to increased anxiety. Boys with autism show increased brain and body size at birth and infancy, as well as later overgrowth, which correlates with greater severity of social deficits and poorer verbal skills-reflecting less domesticated features.

Children and adolescents with autism have higher levels of male sex hormones, which also correlate with the severity of autistic traits. This might account for the early puberty common in this condition.

Women with autism report significantly more irregular menstrual cycles and dysmenorrhea, and delayed age of menarche seems to correlate with the severity of autistic traits. If a female is less domesticated, she is less "female," and testosterone has much to do with this.

At the other extreme, people with schizophrenia exhibit overdomesticated traits. Schizophrenic brains are smaller than average. The change is marked by a reduction in grey matter that is also associated with longer duration of illness and a poorer response to antipsychotic medications. …

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