To Unlock the Brain’s Mysteries, Purée It

Before Herculano-Houzel’s breakthrough, there was a dominant narrative about the human brain, repeated by scientists, textbooks and journalists. It went like this: Big brains are better than small brains because they have more neurons, and what is even more important than size is the brain-to-body ratio. The most intelligent animals have exceptionally large brains for their body size. Humans have a brain seven times bigger than you would expect given our overall size — an unrivaled ratio. So, the narrative goes, something must have happened in the course of human evolution to set the human brain apart, to swell its proportions far beyond what is typical for other animals, even for our clever great-ape and primate cousins. As a result, we became the bobbleheads of the animal kingdom, with craniums spacious enough to accommodate trillions of brain cells: 100 billion electrically active neurons and 10 to 50 times as many supporting cells, known as glia.

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Suzana Herculano-Houzel holding a wildebeest brain in her lab at Vanderbilt University.

Credit
Jeff Minton for The New York Times

By comparing brain anatomy across a large number of species, Herculano-Houzel has revealed that this narrative is seriously flawed. Not only has she upended numerous assumptions and myths about the brain and rewritten some of the most fundamental rules about how brains are constructed — she has also proposed one of the most cohesive and evidence-based frameworks for human brain evolution to date.

But her primary methods are quite different from others’ in her field. She doesn’t subject living brains to arrays of electrodes and scanners. She doesn’t divide brains into prosciutto-thin slices and carefully sandwich them between glass slides. She doesn’t seal brains in jars of formaldehyde for long-term storage. Instead, she demolishes them. Each organ she took such great…

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