Naked mole rats, as I am sure everybody knows, live underground in such inappropriate conditions for mammals that their skin has evolved not to feel pain and they sustain constant near-suffocation. Also they are blind. Basically they are just pouches of cells with legs and heads and no faces. They live underground in East Africa in tunnels, like ants. The naked mole rat's sperm it turns out is a raisin to most species's grapes, and doesn't even have its genetic material packaged correctly sometimes, and is borderline incapable of movement (only 15% of mole rat sperm cells in the study had a tail motor built well enough to enable swimming). Yong explains why this is unique among animals:
Van der Horst thinks that the rodent’s odd social structure is responsible for its malformed sperm. In many other animals, females mate with many males, or can store sperm inside their bodies. In these cases, the sperm do battle inside the female’s body for fertilisation rights. This “sperm competition” is the norm in the animal kingdom, and it has driven the evolution of longer and ever more elaborate sperm.--Which is the part that interested me the most. Life is inconceivably diverse, but within all that variation there is a general rule that competition rules. Cooperation is not widespread: even within colony-forming animals the runts are unlikely to mate and the elders are left for the some other species's meal; we know all this from Lion King. (The naked mole rat does employ competition among females of the species to replace the only birthing member of the colony, the queen, upon death; but as with ants losing the race to become a reproducing member of the colony probably does not exclude one's genes from regeneration: the sterile portion of the ant colony can influence the gene pool by allocating the best quality nuturing to closer-related offspring of the fertile caste; which is just a guess I am making.)
[...]But the naked mole rat has no sperm competition at all. In any single colony, with around 40 to 90 individuals, the only ones that can reproduce are the queen and her male consort (with a couple of possible affairs on the side). With such fixed fates, there is no reason for the other males to compete for mating rights, and no reason to have Olympic-level sperm.
The mole rat, by staking territory in the most undesirable environment possible, has exempted itself from one of the most universal rules of biology. Thought of in human terms, the naked mole rat is the fictional dwarf society living underground: mining, getting dirty, bur minus the mustaches, and plus eating its own poop. Mole rat colonies will find a huge tuber and nibble on it over a period of years; but young mole rats diet on the feces of their caretakers until they can digest their own food (the naked mole rat's common lifespan is almost 30 years).
There is something of the mythological in the naked mole rat's non-competitive squalor. It is living proof of a communal utopian society that most animals can't stop squirming a shiv into their brother's lungs long enough to even dream of. It seems cut from the same ideas of sharing and equality that power all sorts of our Western tropes and stereotypes, from the slothly dream futures of the mid-20th century where robots would enable us to be sedentary and we could wrap virtual reality visors around our eyes; to the recurring Protestant work-ethic fantasy of the noble savage, whose life is both phyiscally harsh and emotionally untroubled. Normally these contradictory ideas only find their home in the anachronistic fantasy societies of fiction, short furry people who live in caves or treehouses, and forgo competitive systems like capitalism and democracy in favor of sharing and senioriarchy (but also have fantastic technology or riches). That the mole rat actually embodies these contradictory ideas in a workable way is proof of its not belonging to the same rules that govern most of life on Earth.
Funnily enough, the other species to occupy this same rare sphere of social organization, of hierarchical work-sharing replacing open reproductive competition, also live in tunnels: ants, termites, and some wasps and bees. So, it's something about tunnels. Perhaps tunnels are both in biology and in fiction a substitute for stable, authoritarian government: a structure that provides relative security from outside threats, that nourishes the favored and the worker caste alike, but limits freedom and pleasure.