Anna Karenina principle

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The Anna Karenina principle was popularized by Jared Diamond in his book Guns, Germs and Steel to describe an endeavor in which a deficiency in any one of a number of factors dooms it to failure. Consequently, a successful endeavor (subject to this principle) is one in which every last one of the possible deficiencies has been avoided.

The name of the principle derives from Leo Tolstoy's book Anna Karenina, which begins:

Happy families are all alike; every unhappy family is unhappy in its own way.

(Russian: "Все счастливые семьи похожи друг на друга, каждая несчастливая семья несчастлива по-своему")

Diamond uses this principle to illustrate why so few wild animals have been successfully domesticated throughout history, as a deficiency in any one of a great number of factors can render a species undomesticable. Therefore all successfully domesticated species are not so because of a particular positive trait, but because of a lack of any number of possible negative traits.

From chapter 9 of Guns, Germs and Steel, 6 groups of reasons for failed domestication of animals are:

• Diet - To be a candidate for domestication, a species must be easy to feed. Finicky eaters make poor candidates. Non-finicky omnivores make best candidates.

• Growth Rate - The animal must grow fast enough to be economically feasible. An elephant farmer, for example, would wait 15 years for his herd to reach adult size.

• Problems of Captive Breeding - The species must breed well in captivity. A species having mating rituals prohibiting breeding in a farm-like environment make poor candidates for domestication. These rituals could include the need for privacy or long, protracted mating chases.

• Nasty Disposition - Some species are too mean and nasty to be good candidates for domestication. The farmer must not be at risk of life or injury every time he enters the animal pen.

• Tendency to Panic - Species are genetically predisposed to react to danger in different ways. A species that immediately takes flight is a poor candidate for domestication. A species that freezes, or mingles with the herd for cover in the face of danger, is a good candidate.

• Social Structure - Lone, independent species make poor candidates. A species that has a strong, well defined social hierarchy is more likely to be domesticated. A species that can imprint on a human as the head of the hierarchy is best. Different social groups must also be tolerant of one another.