While IQ scores are rising at a remarkable rate, humans' underlying genetic potential for smarts could be on the decline, a new study suggests. The research found that by one measure of intelligence, the Victorians had modern folk beat.

The findings aren't without controversy — particularly whether or not the measurements used really reveal intelligence. Still, the study highlights the trouble with measuring intelligence over time: Smarts aren't defined as just one thing. What makes a person clever on the African Savannah could be nearly useless in the financial centers of Hong Kong.