Human faces continue to grow until the age of around 20, but the brain reaches around 95 per cent of its adult size by age 6.
If the fossil children – with near fully developed brains – resemble living ones, but fossil adults had very different skulls, we can rule out that brains have changed significantly in shape, says Zollikofer. “And if it’s not the brain driving this change, we must look for something else, like breathing, eating or moving.”
