Our brains have been shrinking for millennia: science is very clear about why (and no, it doesn't mean we're getting dumber)

A study suggested the human brain shrank about 3,000 years ago, but a later review challenged that timing on methodological grounds.

The review argues the reduction may have started earlier or happened gradually across the late Holocene.

Both sides agree that brain volume does not strongly predict cognitive performance or intelligence.

The debate points to evolutionary changes shaped by social, energetic, and biological adaptation rather than simple brain size.