Recap: The Great Move

Every land vertebrate is a variation on this migration story. Limbs, lungs, necks, wrists, and ears all trace back to animals that were still partly aquatic.

Evolution did not plan a conquest of land. It rewarded fish that could survive shallow, messy margins - and those margins eventually produced amphibians, reptiles, mammals, birds, and us.

The Hiccup Clue

Your hiccups may be a leftover from that watery past. The reflex appears to reuse a neural circuit much like the one a tadpole uses to push water across its gills.

For a split second your body runs an old aquatic program: a sharp intake, then the throat snapping shut — the same move that once kept water out of a breathing passage. It is only a leading hypothesis, not proven, but it is a striking hint that deep instructions can outlast the bodies that first used them.