Lucy's Posture Never Built Our Brains

Paleontology has a reliable tell. Find the anatomical feature that looks modern, work backward through deep time. Claim it as the origin story of something we care about today.

A throat structure in a Mesozoic predator becomes the seed of human cognition. The public reads it as causation — and nobody asks for the mechanism that connects a 66-million-year-old mammal's larynx to what happened after the dinosaurs died.

This echoes a specific reversal that should have changed how paleontology writes its stories. In the 1970s, Donald Johanson's discovery of Lucy — Australopithecus afarensis. Was presented as proof of an iron law. Bipedalism drove brain expansion in our lineage. But subsequent fossils showed that brain volume didn't expand significantly until Homo arrived, more than two million years after Lucy's species perfected bipedal locomotion.

The structural mistake repeats exactly. Take a feature that exists in two things and assume the earlier one caused the later one. Lucy's posture and human brains are separated by evolutionary distance and two million years of unrelated pressures. This predator's throat and human language are separated by an extinction event and multiple mammalian lineages with no fossil trail connecting them. Correlation across deep time collapses under scrutiny.

The feature that feels causative often isn't.

What changes when you see this pattern is how you evaluate any claim about your own work that rests on an origin story nobody can trace. When someone tells you that your early success in one domain caused your expertise in another, ask for the mechanism. When you're tempted to retrofit your career backward from where you are now, treating every small choice as inevitable preparation, resist it. The feature that feels causative often isn't. You succeeded at the first thing for entirely different reasons than the second thing required. The gap between correlation and causation doesn't close just because the narrative feels seamless.