“His brain is amazingly plump.” That’s what Sandra Witelson says of Albert Einstein in this interview in last week’s New York Times. In 1999, she found that Einstein’s parietal lobe was bigger than average, and unlike everyone else’s parietal lobe, it wasn’t divided by the Sylvian fissure.

Witelson has built a career studying the human brain. At McMaster University, she studies a brain bank filled with donations from cancer patients who went through a battery of physiological and some psychological tests before death. So, she can correlate these measures with human brain anatomy.

Witelson has some interesting findings on sex differences in the human brain. In a 1995 Journal of Neuroscience paper, she found that women have 11% more neurons in cytoarchitectonic area TA1, a portion of the temporal lobe that is thought to be involved in language. Unlike her study of Einstein’s brain, which makes for great cocktail party conversation, her studies of sex differences in the brain have become politically charged, quoted most recently by the supporters of Lawrence Summers, the embattled former president of Harvard.

Personally, I’m far more surprised by anatomical differences in Einstein’s brain than in anatomical differences between the sexes. At the very least, male and female brains are bathed in different hormones that could influence gene expression, cell division and cell death throughout development. So what was Einstein’s brain bathed in, and how did it develop so unusually?