The human brain, more than any other attribute, sets our species apart. Over the past 7 million years or so, it has grown in size and complexity, enabling us to use language, make plans for the future and coordinate with one another at a scale never seen before in the history of life.

But our brains came with a downside, according to a study published last week. The regions that expanded the most in human evolution became exquisitely vulnerable to the ravages of old age.