Why Do We Have two Kidneys?

After consulting many people, now one was able to tell me why we have two kidneys in our bodies? we have one heart, one stomach, but why two kidneys? As humans we only need one kidney to live. After doing some research the only reliable answer i found is that the kidneys like the eyes, ears, and lungs it was made to be symmetrical. It may be that it was provided because if one was to fail we would have another to preform the functions, since the functions of the kidneys is to filter waste out of the bloodstream and is responsible for eliminating toxins and poisons from the body through the urine, and that same blood will be purified and will flow to parts of the body, especially the HEART (the most important organ). It is a very vital organ that needs a back up! because without it we would be in BIG trouble. If both kidneys were to fail the body would die in 2-3 days because of the toxins entering the body. 

Different Kidney Diseases