I have noticed that there are individuals who are quite astounding as to their appearance and the way they talk and body language, that is so much like others they resemble in many ways. I do not believe that there are actual dopplegangers on this planet, but if you want to use your imagination, think about in other worlds similar to our own in other galaxies. Could there be others who have evolved and developed just as we and look like us or have there been such a wide range of genetic or inherited traits all around the earth that we have all been a part of over the eons, that it would be impossible for this to happen? If, say a billion planets were examined, and on these planets, say, a million of them had very similar environments and qualities, and you could compare the inhabitants in a given climate to each individual planet, could there be actually dopplegangers on these planets, or is there just too many genetic accidents or variables that prevent this from taking place? I once saw a sci-fiction as a teenager about just such an event. It was quite interesting to me and stirred my imagination quite a lot.