One of the most unusual, bizarre-looking and fascinating animals known to science is found in the arid earth of sub-Saharan Africa. It lives in subterranean colonies, with a single breeding queen. It has a worker caste that takes care of the young animals and soldiers that defend the colony: It is "eusocial" -- truly social, like ants in a nest or bees in a hive. But this is not a social insect -- it's one of us, a mammal.

The naked mole-rat is a rodent, the only known vertebrate that lives in such a "hive" society, with a caste system more commonly associated with insects than mammals.

Farmers in Kenya, Ethiopia and Somalia have been aware of naked mole-rats for years. They saw the mounds of earth pushed up in molehills and knew that some kind of animal was eating the succulent tubers and roots of the plants that grow in the hard soil. But the unique social system of the naked mole-rat was not guessed at until 20 years ago, when an evolutionary theorist was put in touch with a biologist working in Nairobi.