Book Review: Made for Each Other: The Biology of the Human-Animal Bond by Meg Daley Olmert

A nursing mother, a pet lover and a horse in a cavalry charge have at least one thing in common: bloodstreams full of oxytocin, Olmert contends in this fascinating book that explores the deep connection between people and animals.

Many studies have linked oxytocin, one of several mammalian hormones produced in the hypothalamus, to maternal bonding, trust and social recognition in several species.

In pregnant humans, a surge of oxytocin stimulates labor. Once a baby is delivered, the neurochemical induces the mother to release breast milk — an elegant symbiotic design that keeps babies fat and happy and can send nursing mothers into a state of dreamy contentedness. At the other extreme, mice genetically incapable of producing oxytocin can’t recognize mice that they’ve previously encountered.

Studies show that stroking pets increases levels of oxytocin in the groomer and the groomed, and the hormone’s calming effects may explain the benefits of pet therapy, the connections people forge with individual animals and people’s love for animals in general.

Olmert suggests that oxytocin has played a key role in domesticating large mammals and turning them into pets. In horses, for instance, a naturally high level of oxytocin — boosted in the species by evolution and in individuals by a bond with a nurturing horseman — may be key to transforming the gentle creatures into warhorses capable of galloping headlong into the noise and confusion of a battlefield.

This work also explores how urban dwellers become increasingly disconnected from nature and animals. One thought: Rising rates of nervousness and depression could be signs of a population suffering from oxytocin deprivation.

>Da Capo Press, 2009, 320 p., $26