Almost 700 years ago, a Dutch naturalist envisioned a fish with arms that would enable it to climb out of the water, setting the stage for terrestrial life. Now, it turns out, his fantasy had roots in reality. Researchers studying skeletons of the finger-size zebrafish have discovered mutants that grow extra bones in their front fins. The mutations unleash the same sets of genes that give rise to our own forearms, demonstrating that—even early in animal evolution—the potential for making landfall was already in place.