Humans are the only animals that have chins.
Why it is true
Even our closest primate relatives, like chimpanzees and Neanderthals, lack a protruding chin. Scientists believe it evolved due to changes in human speech or diet.
Source: Anthropology
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This is the reading side of the site, so the answer is in the sentence above — that is the whole point of it. Test yourself works the other way round: the question comes on its own, and the fact and the explanation only appear once you have answered.