Question

what is the reason of human have two kidney

Answer 1

humans have two kidneys in case if one is damaged then other may work.

Answer 2

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Most humans are born with two kidneys as the functional components of what is called the renal system, which also includes two ureters, a bladder and a urethra. The kidneys have many functions, including regulating blood pressure, producing red blood cells, activating vitamin D and producing some glucose.