Anna Karenina principle

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", six 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 perhaps 12 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. The zebra is of special note in the book, as it was recognized by local cultures and Europeans alike as extremely valuable and useful to domesticate, but it proved impossible to tame. Horses in Africa proved to be susceptible to disease and attack by a wide variety of animals, while the very characteristics that made the zebra hardy and survivable in the harsh environment of Africa also made them fiercely independent.
*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. Deer in North America have proven almost impossible to domesticate, and have difficulty breeding in captivity. Horses, however, immediately thrived from the time they were introduced to North America in the 1600s.
*Social Structure - Species of lone, independent animals 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.

The term is also used in science.

* In statistics, the term is used to describe significance tests: there are any number of ways in which a dataset may violate the null hypothesis and only one in which all the assumptions are satisfied.
* In ecology and in particular ecological risk assessment:

Successful ecological risk assessments are all alike; every unsuccessful ecological risk assessment fails in its own way. Tolstoy posited a similar analogy in his novel Anna Karenina : "Happy families are all alike; every unhappy family is unhappy in its own way." By that, Tolstoy meant that for a marriage to be happy, it had to succeed in several key aspects. Failure on even one of these aspects, and the marriage is doomed . . . the Anna Karenina principle also applies to ecological risk assessments involving multiple stressors

(Moore 2001).

References

* Moore 2001. "The Anna Karenina Principle Applied to Ecological Risk Assessments of Multiple Stressors". Human and Ecological Risk Assessment, Volume 7, Number 2, pp. 231-237(7)