The group known as humans includes ourselves and a collection of related species, proto-humans such as Neanderthal man. We and these relatives are all obligate tool users meaning that the making and use of tools has become an intregal part of behaviour without which we couldn't survive. A big brain is another characteristic of genus Homo, though the actual size may vary. Homo habilis has the smallest and Neanderthal man the largest, with our own modern brains taking second place.

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