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<\/div>Nobody\u00a0 doubts that Albert Einstein<\/a> had a brilliant mind. But the Nobel prizewinner, famous for his theories of special and general relativity, wasn\u2019t blessed with a big brain. \u201cIt was smaller than average,\u201d says Jeremy DeSilva<\/a> at Dartmouth College in New Hampshire.<\/p>\n This seems surprising. Big brains are a defining feature of human anatomy, and one we are proud of. Other species might be speedy or powerful, but we thrive using the ingenuity that comes with a large brain. Or so we tell ourselves. Einstein\u2019s brain hints that the story isn\u2019t so simple \u2013 and recent fossil discoveries confirm this. Over the past two decades, we have learned that small-brained hominin species survived on Earth long after big-brained ones appeared. Moreover, evidence is growing that they were behaviourally sophisticated. Some, for instance, made complex stone tools that could probably only have been fashioned by individuals with language.<\/p>\n These discoveries turn the question of human brain evolution on its head. \u201cWhy would selection favour big brains when small-brained humans can survive on the landscape?\u201d says DeSilva. Neural tissue consumes lots of energy, so big brains must surely have brought benefits to the few species that evolved them. But what?<\/p>\n An answer to this puzzle is beginning to emerge. It looks like brain expansion began as an evolutionary accident and then led to changes that caused this growth to spiral. Surprisingly, the sorts of changes that drove this expansion could also explain a more recent 10 per cent reduction in human brain size. What\u2019s more, this suggests our brains may shrink further still \u2013 and might even cause humanity\u2019s demise.<\/p>\n It is undeniable that\u2026<\/p>\n<\/p><\/div>\n