Have you ever tried to draw a brain? I find it hard to get the wrinkles to look right. Scientists at at the University of Jyväskylä in Finland made a solid model of a fetal brain out of gel that developed its own realistic furrows just by dunking it into a solvent.
From BBC:
They made a solid replica of a foetal brain, still smooth and unfolded, and coated it with a second layer which expanded when dunked into a solvent.
That expansion produced a network of furrows that was remarkably similar to the pattern seen in a real human brain.
This suggests that brain folds are caused by physics: the outer part grows faster than the rest, and crumples.
