  A third hybrid definition, also disjunctive, is the cladistic definition defended by Stephen Davies.  who holds that something is art (a) if it shows excellence of skill and achievement in realizing significant aesthetic goals, and either doing so is its primary, identifying function or doing so makes a vital contribution to the realization of its primary, identifying function, or (b) if it falls under an art genre or art form established and publicly recognized within an art tradition, or (c) if it is intended by its maker/presenter to be art and its maker/presenter does what is necessary and appropriate to realizing that intention (Davies, 2015). (In biology, a clade is a segment in the tree of life: a group of organisms and the common ancestor they share.) Artworlds are to be characterized in terms of their origins: they begin with prehistoric art ancestors, and grow into artworlds. Hence all artworks occupy a line of descent from their prehistoric art ancestors; that line of descent comprises an art tradition that grows into an artworld.  So the definition is bottom-up and resolutely anthropocentric. A worry: the view seems to entail that art traditions can undergo any changes whatsoever and remain art traditions, since, no matter how distant, every occupant of the right line of descent is part of the art tradition. This seems to amount to saying that as long as they remain traditions at all, art traditions cannot die. Whether art is immortal in this sense seems open to question.  A second worry is that the requirement that every art tradition and artworld stand in some line of descent from prehistoric humanoids makes it in principle impossible for any nonhuman species to make art, as long as that species fails to occupy the right location in the tree of life. While the epistemological challenges that identifying artworks made by nonhumans might pose could be very considerable, this consequence of the cladistic definition’s emphasis on lineage rather than traits raises a concern about excessively insularity.