“Boulevard du Temple”, taken by Daguerre in 1838 in Paris, includes the earliest known photograph of a person. The image shows a street, but because of the over ten minute exposure time the moving traffic does not appear. At the lower left, however, a man apparently having his boots polished, and the bootblack polishing them, were motionless enough for their images to be captured.
Nobody knows who the man is in the photo. Daguerre wasn’t intending to take pictures of any people that day, and it would only have been possible if someone decided to stand still for a while. So he didn’t know that he’d captured a person until he developed the plate.
Somewhere, a man lived out his entire life unaware that he was the first person ever photographed. It’s possible he never even saw a daguerreotype. He was just going about his day and stood still in just the right place for just the right length of time and now the photograph is studied because he’s in it. And we don’t know who he is, and he never knew who he was (in a historical sense) either.