For centuries, scientists have wondered what makes humans so much smarter than other species. Some proposed it was the size of our brain (though that didn't explain why whales weren't smarter than us); others thought it was the size of our brain relative to our body size (but there were problems with that explanation as well). In this episode, neuroscientist Suzana Herculano-Houzel lays out the mystery of the "Human advantage," and explains how a new technique she invented several years ago has shed light on some of these longstanding mysteries.