Each year, monarch butterflies migrate across North America, tracing a precise route around Lake Superior—even though no single butterfly has ever made the full trip before.

But here’s the strange part: their flight path curves in a way that suggests they’re navigating around something that’s no longer there. Scientists believe that centuries ago, this detour made sense—because they were avoiding the Ancient Lake Superior Highlands, a long-eroded mountain range.

Today, those peaks have crumbled into gentle hills. But the butterflies still follow the old curve, guided not by memory in the usual sense, but by genetic memory—an inherited map embedded deep in their DNA.

It’s a mind-bending example of how evolution stores the past in living creatures, even when the landscape forgets.