The article is about a rock that archaeologists found that they think is a crayon from hunter gather times. There seems to be a lot of speculation but there are things that use science like comparing the rock to naturally formed rocks and seeing a difference that suggests that is has been formed by humans. It might be a way to see more about how humans at that time learned to communicate with each other in a way that we can study. The picture helps to let the reader see the rock and to understand how archaeologists could have come to their conclusions. To me it looks more like a piece of chalk than a crayon especially when they would have been writing on rock walls instead of the normal walls of a building that children draw on now with crayons.
Objects from a culture can help to show through analysis the aspects of that culture that can not take material form. (Paraphrase of a part of the Haltman text)