Some 500 million years ago, an ancient fish-like creature produced at least one offspring with a curious mutation — twice the number of genes. These excess genes began developing in new directions, eventually creating more and more complex brains. Some 150 million years later, human ancestors roamed the land, and their brains continued to grow in complexity. About 2.5 million years ago, hominid brains started growing especially large, although scientists aren't exactly sure what led to that sudden burst. Yet after millions of years of evolutionary experimentation, the human brain is a biological wonder many times more efficient than any artificial equivalent — in fact, it's even more efficient than a 60-watt lightbulb.
Take, for example, IBM's Watson, the supercomputer that famously bested Jeopardy! champions on daytime television in 2011. Watson uses around 85,000 watts to electronically outfox a human. Meanwhile, its biological competitors' brains run at around 20 watts. It's true that when compared to the rest of the human body, the brain is a greedy customer, requiring about 20% of our energy use. It uses two-thirds of that energy to send signals along its neurons, and the rest for cell-health "housekeeping." But when it comes to everything our brains do for us — and how efficient they are overall — that seems like energy well-spent.
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