If Humans Are Getting Smarter, Why Are Our Brains Shrinking?

Over the past two decades, some studies have suggested that human brains are shrinking. Yet IQ scores have risen. Live Science spoke with experts to find out if we can get smarter as our brains shrink.

Einstein's extraordinary brain folding patterns may account for his genius. Studies show little to no relationship between intelligence and brain size in humans.

Maciej Henneberg, professor emeritus at Adelaide University, says human brain size declined by about 10% (150 ml) during the Holocene, which began 11,700 years ago. He analyzed skulls from around the world.

Jeremy DeSilva and Jeff Stibel confirm a global trend toward smaller brains. Stibel says the Holocene warming period coincided with more than a 10% reduction.

Not all agree. Brian Villmoare of UNLV says there is no evidence of meaningful brain change. John Hawks of UW-Madison notes datasets overrepresent European men, and brain size rebounded in industrializing countries over the last 150 years.

Theories include the shift to farming, which reduced need for brute strength and favored smaller bodies. Warming after the Ice Age may also play a role. DeSilva and Stibel suggest that population growth, specialization, and collective intelligence reduced individual brain size, similar to eusocial insects like ants and wasps.

Large brains are metabolically expensive, consuming 20% of resting energy. During food scarcity, larger brains could lead to starvation. This doesn't mean humans are smarter or dumber; our intelligence has simply changed.

Stibel says, "We've likely traded some raw computational capacity for the ability to leverage collective intelligence."