Scientific studies indicate that while the brain overall is shrinking, the frontal lobe – that part of the brain responsible for communication, planning and executive function, among other things – is growing. No one knows why for certain, but there are a lot of theories. Could it be related to the birth of reading and writing? Also interesting is an apparent increase in sexual dimorphism:
The 7,000 years or so these endocasts cover is also the period writing was invented and spread around the world; until many countries have almost universal literacy rates. In other words, as reading and writing becomes more important the region of the brain needed for it becomes larger, despite the fact the rest of the brain is shrinking. It’s a “no duh” question; but could there be a link? The researchers think so1, but it is worth noting the frontal lobe is also linked to planning and memory.
The team also found that there had been an increase in the differences between the sexes (sexual dimorphism) over this time. In the earliest skulls they examined there was only ~150 ml difference between males and females. In present day populations this shot up to almost 200 ml1. This is particularly interesting given the course sexual dimorphism of the body has taken over human evolution. In our early ancestors it was massive, with men being much taller than women. Over time it decreased; but not seems to be increasing again5. In other words it’s followed the same sort of path as brain size, reversing course quite recently.