Animals are sort of modeled after trees in that they basically live in the same landscape all their lives. Even though they move, they stick to pretty much the same landmarks and pathways for their entire lifetime. They watch the same landscape grow and change over the seasons and the years much as do trees.
People, on the other hand, are always changing the landmarks we notice and the pathways we follow. Rather than watching the same landscape change over time, like trees, we watch time change, as measured out in different landscapes.
Thus, man the nomad who explored the world…