Male and Female Brain Anatomy: A Continuum Rather than a Binary
In the online Science magazine, an article by Kate Wheeling titled, “The brains of men and women aren’t really that different, study finds” reports on recent research debunking the previous claim that men and women have distinctly unique brain anatomy. In fact, the layout of brain looks more like a “patchwork” where some structures are more common to men and some are more common to women, but nothing concretely different. For example, the left hippocampus was usually larger in males than in females, but some males had a left hippocampus smaller than the average size for a female. Wheeling describes how the brain has been portrayed in binary terms, even though the evidence to support such claims has been exaggerated and overused. The amygdala, a common example, is generally larger in men than in women, but there is considerable overlap and its size is environmentally dependent.
The new study, which looked at over 1400 different brains, was performed at Tel Aviv University in Israel using existing MRI scans. The results showed very few structural differences between men and women. However, there was variation in size of brain structures that was vaguely related to sex. The team approached this relatedness by creating a continuum from “maleness” to “femaleness” in terms or structure size, but in reality most brains “were a mosaic of male and female structures.” Whether they looked at gray matter, white matter, or the diffusion tensor imaging data (“which shows how tracts or white matter extend throughout the brain”) only 0–8% of brains were composed of solely “male” or “female” structures.
Daphna Joel, head of the research team believes these results provide evidence that there is little biological basis for why men and women behave differently.
“There is no sense in talking about male nature and female nature,” Joel says. “There is no one person that has all the male characteristics and another person that has all the female characteristics. Or if they exist they are really, really rare to find.”
Joel believes that this study will have long-lasting and important implications, such as ending male and female comparisons in brain research. Not everyone agrees with Joel that this is the correct direction for science, and while neuropharmacologist, Margaret McCarthy, believes that the results in this study “contribute in an important way to the conversation” she also believes that it is still necessary to study sex differences found in the brain.