Complex behaviors reveal remarkably simple genetics

The simple entrance of this oldfield mouse burrow should not mislead you about its architectural complexity.

Vera Domingues/Hopi Hoekstra, Harvard University

Humans engage in a lot of complex behaviors, but many of them are learned. Genetics gives us a nervous system that's flexible enough to incorporate new behaviors, and we pick them up socially. But many animals display highly complex behavior that appears to be instinctual. Which raises the question of how these sorts of behaviors can be programmed into the nervous system genetically.

Pretty simply, if a new study of mice is to be believed. The work compared the architecture of burrows built by two closely related species. The researchers find the design of the animals' burrows is modular, and the two modules are largely controlled by a handful of genes—perhaps as few as four in total.

The work relied on two closely related species. One is the deer mouse, which is widespread in North America. This species makes very simple burrows, with a short entry passage leading to a nest. In the southeastern US, however, there's a closely related species, the oldfield mouse, that builds a far more complex home. This includes a much longer entrance passage and a secondary "escape tunnel" from the back of the nest that allows it a safe route out should a predator come in the front door.