Male and female brains are wired differently according to this article: Maps of neural circuitry showed that on average women's brains were highly connected across the left and right hemispheres, in contrast to men's brains, where the connections were typically stronger between the front and back regions. But since learning in the brain is associated with changes of connection strengths between neurons, this could be or not the result of learning. What about physical differences from birth? Are there differences in size, regions, chemical composition, etc. from birth?