you said that humans have not evolved from any monkeys or primates and that humans and monkeys both had a common ancestor. but where has that ancestor gone??
In some cases, newly evolved species end up out-competing their parental (or sibling) species, driving them to extinction, but by no means in all cases. Otherwise, there would always be exactly the same number of species on the planet.
Also there are monkeys still around because, like us, not all species of monkeys have yet gone extinct.
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