Here is a drawing of the pencil head species evolve/grow up over time. As you can see when the pencil head is first born they look like basic wooden pencils with a basic-looking body, as they grow up they use their pencil head's to draw their bodies. Once the pencil heads reach around their teens their heads begin to look more like mechanical pencils and over time they draw their bodies with more detail. When pencil heads reach adulthood their heads look more like pens, representing how they make fewer mistakes.