Amanda's concluding sentences was "All told, what's striking about the evidence on language is not so much a profound gap between the sexes, but the large gaps in our understanding of the brain." Exactly so.

I found it curious, though, that the case for sexual dimorphism was so poorly argued by the authors as to invite repudiation and rejection. Surely a stronger case can be made from existing evidence?

Turns out not.

The theory of sexual dimorphism in brain structure got a lift in a 1982 Science Magazine article claiming that the corpus collosum, a bundle of nerves which connect left and right hemispheres, is much thicker in women than in men. This observation gave rise to a cottage industry of theorists and speculators who used it to reinforce folk wisdom about multi-tasking women and one-task-at-a-time men, gatherers and hunters. Women, it was argued, clearly have a brain structure which facilitates use of both hemispheres simultaneously. In men, they're either calm, rational, and logical (left brain dominant), or they are emotional and out of control; a true "Jekyll and Hyde" split personality, two brains in one head. The latest books reviewed by Amanda are variations on the same enthusiastic theme.

Unfortunately, that 1982 study has been completely, thoroughly debunked. The corpus collosum in men is not smaller; it may even be larger, according to more recent research.

That's been the trend for sexual dimorphism advocates. Their science is loosy-goosy, and they are quick to extrapolate from scanty data to monumental conclusions. But we should not be too hasty to conclude that there are no differences. Anyone who has spent time with small toddlers of both genders will tell you that boys and girls are behaviorally different, in profound ways.

And although Dr. Deborah Tannen's now-classic book on language and gender "You Just Don't Understand: Men and Women in Conversation" is highly anecdotal and not exactly rooted in the hard sciences, she's clearly onto something.

Likely, neuron-density of particular sections of the brain is simply too crude a measure to be of much practical value. The mysteries are deeper, more subtle, and they involve not so much brain structure as the incredibly flexible programmability of those brains and the influences of gender-specific hormones upon them.

It'll be a long while before science teases out answers. Forget rocket science; that's easy compared to brain science.