D: For the longest time scientists have thought that only particular species of insects      were eusocial, but did you know that they have recently discovered that a certain      mammal is eusocial? And it's the sausage with fangs, the mole rat.

Y: Yuck. Why don't you keep your metaphors to yourself and start by telling us what it      means for a creature to be eusocial.

D: A species of insect is eusocial if it meets these main criteria. Many adults, including      various generations of them, live together as a colony. They cooperate in building the      nest and caring for the young. And there is some form of a reproductive hierarchy.      Often this means there is a single queen who births all of the colony's offspring. Bees,      ants, wasps, and termites are all examples of eusocial critters.

Y: Sounds good, but there's one thing you might clarify, particularly since it is the very      detail that held scientists back from classifying the naked mole rat as the first eusocial      mammal, that is until recently.

D: What's that?

Y: For a creature to be considered eusocial there should be some permanent physical      trait that distinguishes castes of the colony from one another. For instance, the queen      ant has wings, but the worker ants do not. In the case of the mole rat, the queen has      specialized vertebrae that make her body longer than her cohorts. The extra length      allows her to fit through the narrow tunnels of the home despite carrying up to      twenty-seven fetuses at a time.

D: Twenty-seven? Yikes. I guess that's the downside of being the queen of the colony.      Can you imagine if humans were eusocial?

Y: That's not something I care to think about.  

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