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Using fossil records to measure cranial capacity through the millennia, researchers have found that as we become increasingly domesticated as a species, the size of our brain continues to shrink. Bruce Hood, psychologist at the University of Bristol, UK, says shrinkage is best explained by changes in society: "We have been self-domesticating through the invention of culture and practices that ensure that we can live together." Hood notes that as humans have domesticated other species, from cows to dogs, their cranial capacity has also shrunk as they learn to enlist the help of their human masters rather than invent their own solutions.
What's the Big Idea?
Where our brains have lost capacity, our ability to share knowledge across society has blossomed. This is what, according to Hood, has made our species so successful. "Knowledge can be broadly distributed, disparate areas of expertise collaboratively coordinated, and technology can develop over many generations." Our dependency on shared knowledge at the community level, however, is also ripe for abuse. "The importance we place on allegiances, for example, is all too easily manipulated by unscrupulous leaders, and deplorable actions are too readily committed through what Hood calls 'diffusion of accountability'."