If you go far enough back along the branch of the evolutionary tree of life that humans sit on, you get to the part near the trunk where verterbrates (creatures with spines) split from invertebrates (creatures without spines). Current theories suggest the complex brain we share with our vertebrate relatives appeared after this point, but now, thanks to a marine worm with a proboscis that burrows into sand on the sea floor, a new study from the US is challenging that view...
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