What Isn't?

One of the focuses of Davis's essay, Historical Narratives and the Philosophy of Art, revolves around a question that seems to have no definite answer--What is art? According to various definitions, art can be as concrete as a simple painting, clay sculpted into familiar forms, or even something carved out of a piece of rock. Art could also be something that doesn't even exist because for some, art isn't the finished product, its the process that an artist goes through to make that piece. An example of this concept would be what an artist does to make him different from the norm, to break free from the usual and rebel by projecting his new ideas, "...An ambition to do it differently from predecessors or, like Hesires's sculptor, to be "inventive" or the like" (334). Later on in the essay, Davis goes on to talk about what he thinks constitutes art; what its composed of, how it must be something comparable, how its a "replication and summation" of something of the past, etc (331). With all these factors into what makes art art makes me wonder, what isn't art?
No disrespect but, it seems to me that just about anything and everything can be classified as a work of art simply because of the fact that this matter is extremely subjective; therefore, there is no exact answer as to "what is art"? Towards the end of the essay, Davis mentions these four marked bones from Bilzingsleben, that possess some very interesting marks on each one of the bones. "Forensic inspection shows that all the lines on each bone were cut by 'the same tool,' probably 'in the course of one single process.' Among the four bones, however, different tools were used..." and the marks varied in length, size, orientation, number and pattern (343). For some, people thought of these bones as art that demonstrated "abstract thinking" of the Homo erectus (344). For others however, individuals (including myself) were a bit skeptical of this issue because they argue that no, these bones aren't works of art, they're just bones that happen to have marks or scratches on them brought upon my natural events. "Forensic analysis...quickly implied that the markings could be the nondeliberate by-product of other processes, either natural processes or hominid activities such as defleshing the bones or using them as cutting platforms" (344). Now, my question is, is art still art if someone else doesn't think it is?