← Trends in human evolution

5 Cranial & skeletal trends over time

Trends from early hominins → modern humans

Feature	Trend over time
Cranial capacity (brain)	Increases greatly (~400 cm³ → ~1350 cm³)
Brow ridges	Reduce / disappear
Face (prognathism)	Flatter: jaw & face less projecting
Teeth & jaw	Smaller (softer, cooked diet)
Sagittal crest	Lost (smaller chewing muscles)
Chin	Appears (a defining Homo sapiens feature)
Skull height	Higher, rounder cranium (more forebrain)

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Explaining a trend

For each trend, state the change AND a reason/advantage: e.g. “teeth got smaller because tool use and cooking made food easier to chew, so large jaws were no longer selected for.”

A fast check before writing about a cranial trend

• Have I stated the DIRECTION of the change, not just named the feature?
• Have I given a functional reason for the change, not just described it as "an improvement"?

Practise just this