Man, I fully expected this article to be the equivalent of "Was historic person gay? Here's loads of examples of them being very gay. I guess, we don't know, if they were more than good friends after all.".
But then while reading, I got convinced they were listing so many cool examples of art, because they wanted to argue that yes, it is art. Only for them to jump back in the conclusion to the ol' animals might just be good friends.
Can you look into the heads of other humans? No, you cannot. What if evolution caused them to say that they make art, because that turns on the ladies? I guess, we'll never know, whether humans make art.