Under the parched desert of Somalia, southern Ethiopia and eastern Kenya lives a mysterious, underground society whose members serve a despotic queen.

Her subjects toil in the darkness, digging a vast labyrinth of tunnels in search of food. They shun sunlight and outside contact, blocking the entrances to their fortresses to keep out invaders. And they forsake their own reproductive drives, spending their lives raising the queen's many children.

To a nonscientist, the description sounds like science fiction. To most biologists, it might call to mind social insects such as bees, ants and termites. But this society's members are much more closely related to humans than to any insect. They are, as the few biologists who know about the species call them, naked mole-rats.

Once considered a self-effacing little rodent of slight scientific interest, the naked mole-rat has become a hot property among researchers who study the evolution of animal social systems. The species' very existence goes to the heart of what Charles Darwin called the most difficult question raised by his theory of evolution. Since the theory holds that each individual is driven to pass on its own genes, how can a society evolve in which most adults sacrifice their own reproductive potential to help another individual reproduce?

'Missing Link' in Social Systems

Biologists often explain the insect societies by pointing out that the genetics of ants, bees and wasps differs from that of other animals. But when Jennifer U.M. Jarvis, a professor of zoology at the University of Capetown, South Africa, reported in 1981 that Africa's naked mole-rats had a similar social organization, her discovery shattered the belief that only insects were capable of evolving along such behavioral lines. At first, some scientists flatly refused to believe it.

Paul W. Sherman, an associate professor of biology at Cornell University and chief editor of a new book about naked mole-rats being published in December by Princeton University Press, recalled the first time he saw a captive colony in Jarvis's laboratory.

"Talk about a scientific thrill," he said. "I looked at these little animals and I thought, 'These really are a missing link in the social systems between insects and mammals.' "

The center of all the attention is a creature that looks like a three-inch-long, wrinkled grayish-pink sausage with skinny legs and buckteeth. No one could love a naked mole-rat for its looks. But spying on the life of a captive colony, like the ones in Plexiglass "burrows" in Sherman's laboratory, is another story. Several American zoos have acquired colonies, and the National Zoo here is "seriously considering it," according to William Xanten, associate curator of mammals.

Mating 'Not a Competitive Affair'

Unlike the workaholic social insects, most of the approximately 75 naked mole-rats in a typical colony spend their time relaxing in a central underground nest, where they lie in a heap on top of or under their relatives. Researchers speculate that such togetherness helps them conserve body heat and water, since their hairlessness and low metabolic rate -- the lowest known of any mammal -- make them vulnerable to rapid loss of heat and fluid. "Their whole physiology is very similar to that of a reptile," Jarvis said.

Some of the smaller animals scuttle backwards and forwards down the tunnels leading from the nest, efficiently sweeping out trash with their hind legs and bringing bits of food to the couch potatoes in the nest. Sherman said jobs are apparently performed according to size, with the smaller animals in charge of housekeeping while the larger ones defend the colony. Although the moles are virtually blind, they are exquisitely sensitive to sounds, smells and vibration.

When a visitor to Sherman's lab accidentally jostled the table on which the plastic "tunnels" rested, the knot of naked bodies exploded into action. The biggest adults rushed through the tunnels to guard the entrances. In the wild, mole-rats apparently fight off snakes -- their major predator -- by threatening or attacking them, and by rapidly closing off their tunnels if a snake tries to enter.

The queen, a large, bossy mole-rat with an unusually long back, nurses her babies and nudges the workers on to greater efforts. She chooses from one to three males in the colony as mates. A queen typically has four litters a year, each producing a dozen or more pups. But Jarvis said that sex in the colony is infrequent, brief and businesslike.

Among the males, "mating is not a competitive affair," she said. In fact, it does not even seem to agree with them. The queen's consorts typically lose weight, shrinking and shriveling. "She usually has to work pretty hard to get males to mate with her," Jarvis said.

By some mysterious process, perhaps involving "communication hormones," or pheromones, the queen controls the reproductive systems of all other adults in the colony. Other females do not ovulate, and only the queen and her consorts mate. In the days before the queen gives birth, all of the adults in the colony develop prominent nipples -- although only the queen produces milk.

"To us, they {the nipples} are a signal that the queen is in complete control," said Sherman. "The driving force has got to be that the queen is powerful, healthy and able to produce lots of young."

If a queen dies or is removed, the ensuing battle for succession is worthy of Tudor England. Other adults in the colony suddenly undergo a growth spurt. Some females become savage, fighting and often killing males and rival females by biting them through the head or heart. Sherman said that in the wild, it is possible that such struggles may end with a colony breaking up into two or more smaller groups, each with a new queen. In laboratory colonies, a single female eventually becomes dominant.

Richard Alexander, a biology professor at the University of Michigan, said that mole-rats live in an environment that has favored the evolution of their lifestyle. Their underground tunnel systems are expandable, accommodating large colonies, and are safe from most predators. The wild tubers they eat are abundant, but finding them means digging through rock-hard soil, a task best done cooperatively. Sherman said that when they dig, mole-rats form a sort of bucket brigade, digging with their front teeth and clawing the dirt back, eventually to a "kicker" who spews it out of the tunnel opening.

DNA 'Fingerprinting' Yields Clue

Although mole-rats in the wild almost never venture above ground, their tunnel systems are surprisingly extensive. One system, mapped by a researcher who attached tiny radio transmitters to colony members, contained almost two miles of tunnels. Sherman quotes a Kenyan folk tale in which the mole-rat, warned by the other animals of an approaching flood, crosses the country through his tunnels to join the rest in safety on the slopes of Mount Kenya.

"The implication is, the whole ground is honeycombed with mole-rat tunnels," he said. "Well, this may not be that screwball."

Recent studies by Cornell researchers recently found another clue to why the mole-rats' society evolved. When scientists performed DNA "fingerprinting" on the animals, they found that colonies were so inbred that their genetic fingerprints were virtually indistinguishable. "They're not clones, but they're close to that," Sherman said.

The discovery provides an answer to the evolution problem Darwin posed. Since colony members share so many genes, Sherman and others suspect that they need not have offspring of their own to ensure the survival of their genes. They can achieve the same result much more efficiently by helping the queen raise her litters. A single queen sometimes produces as many as 90 pups a year, and some of Jarvis's queens have been living and breeding in captivity for 16 years.

Like a beehive, a mole-rat colony can be viewed as a "super-organism," in which the members' functions are so highly specialized that they work together as cooperatively as the cells of a single body. "In the mammal world, it's as close as you get," Sherman said.