Why do we like looking at ourselves?

I stumbled upon one of the oldest cave paintings and I realized that although at first sight it doesn’t appear to hold the same intention as a portrait, it actually does. The painting is of the outlines of hands. Back then people didn’t have enough resources like colored paints or paint brushes to create facial features, which is why I am assuming there aren’t any cave paintings of that sort. However, they painted their hands on the wall as a mark of their existence. Which brings up a similar question to “Why do we like looking at ourselves?”  Why do we feel inclined to leave a mark on the world? There are so many questions that can sprout from this cave painting alone. It appears as if whoever was part of it simply put their hand down on the rock and painted around it, but is that what was done? If not, how was the painting created? Where there more outlines of hands on the rock before the painting was found and did they vanish with the years? These are all questions that cannot be answered. The one thing that I am certain of is that this was a way to register their existence similarly to how couples carve their initials into tree trunks or how kids carve their names on desks at school. Even though it’s not an image of them and a lot of other people share that characteristic (hands/initials/names), they know that it’s theirs and that is enough.