To Be Taught, If Fortunate

by Becky Chambers

On Earth, the term invertebrate – anything without a spine – covers an astounding variety of body types. Spiders, sea hares, millipedes, cuttlefish, dragonflies, and clams all fit the bill. By comparison, vertebrates – snakes, zebras, condors, you and me – are tediously similar below the skin. The spine evolved only once in Earth history, and every being with a skeleton can trace itself back to the same root. We follow a basic template: a bilateral arrangement of skull, ribs, and pelvis, typically accompanied by four limbs. We have two eyes, one mouth, and a brain. The inner structure of our limbs is similarly predictable: one large upper bone, two parallel lower bones, the many little bones that form the wrist or ankle, and digits. We’re all working off of the same blueprint.