If it’s not one thing, it’s another: a new hypothesis floating around the scientific community suggests that evolving bigger brains and superior intellect may have led to a dramatically elevated risk of cancer in humans. Thanks, brain. The theory runs like this. Usually cells die off in a controlled fashion—called apoptosis—which allows fresh cells to replace tired old ones. The process allows old malfunctioning cells to be destroyed before they go rogue and grow into tumors. But in order for our brains to grow bigger, our bodies have had to learn to extend the life of cells, delaying apoptosis and in turn increasing the risk of cancer development.