The Human brain is amazing. It uses around 25% of many of our body's metabolic resources (such as oxygen) to operate. This aspect does not, intuitively, seem like an adaptation that would have helped us out if it didn't happen gradually over a long period of time so that the benefits could justify the resource use. But it didn't happen (on an evolutionary scale) over a long period of time.
Its divergence from the slow, expected progress of evolution when compared to other primates' brains seemed to have rapidly occurred over the past 300,000 years or less. This appears to some to defy the basic principle of incremental change over time. Was it was the result of a single mutation - perhaps mitochondrial Eve? If so, a big brain that is uneducated (imagine the first super-genius) isn't as useful as might be imagined. And such a visible mutation might have made that baby a target for destruction by the 'community.'
In any case - I am fascinated by my recent introduction into this aspect of evolution and am hoping people can share scholarly articles and educated insight into this puzzling aspect of evolution. Here's my contribution: