55M Monarchs Can't Be Wrong

The 1-ounce monarch butterfly may have a thing or two to teach us: Each year, some 55 million monarchs make a 4,000-mile multigenerational journey from Canada to Mexico, returning to the same forest, often the same tree, without relying on GPS. How? The insects rely on a unique internal clock that may be the prototype for our own, the Wall Street Journal reports.

Two types of light-sensitive genes guide the butterflies, which breed and die every few weeks en route, leaving the next generation to continue the journey. New research shows the gene working like a stopwatch to create a sense of how much time has passed. That innate chronometer allows butterflies to navigate over astonishing distances. "In its biochemical essence," the Journal writes, "the monarch butterfly is a distillation of time and light, given wing." (More monarch butterflies stories.)