Why do dogs understand people?

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Dogs love humans because, a very long time ago, when humans were still evolving, humans domesticated wolfs.... i don't know how, or why, but they did, and it proved to be a Excellent alliance. Wolfs turned out to be amazing guards, with there amazing sense of smell. So, over the generations, wolfs became more and more domesticated by humans.... Probably because the wolfs that were mean and didn't like humans would runaway usually, so only the nicer, more friendly wolfs would stay behind and be bred with other friendly and nice wolfs to make the domesticated dog that we know and love today.