The Feet Came First
Bipedalism precedes encephalization by millions of years: we walked upright for roughly 3 million years with an ape-sized brain before skulls inflated. Lucy (Australopithecus afarensis, ~3.2 Ma) walked upright with a ~400 cc brain. At Laetoli (3.6 Ma), footprints show a human arch and stride, no knuckles.
| Stage | Roughly | Brain |
|---|---|---|
| Bipedalism | 4+ Ma | ~400 cc |
| Stone tools | 3.3–2.6 Ma | ~500–600 cc |
| Expansion | ~2 Ma onward | 600 → 1,350 cc |
Pitfall: Evolution does not optimize. Walking first wrecked backs, knees, and made childbirth dangerous.
Brains and Bushes
A modern brain uses 20% of resting energy. This was funded by meat and marrow, fire and cooking (which shrank guts), and groups (the social brain). Wide pelvises walk efficiently, but narrow pelvises fit birth canals: human babies are born early and helpless.
The march-of-progress is a lie. Hominin history is a bush: multiple human species coexisted for millions of years. Homo sapiens arose ~300,000 years ago. Non-Africans carry 1–4% Neanderthal DNA.