The question of which lineages (species, or more inclusive groupings such as class or phylum) of animals are conscious, inevitably goes hand-in-hand with considerations of the evolutionary origin of consciousness. This is a logical implication of the broadly Darwinian view of life, on which modern organisms have evolved through descent, with modification, from a small number (perhaps one) of very ancient ancestors.  If a trait is characteristic of a given species, it either arose in that species, or is derived from an ancestor — in which case, it will be present in other species derived from that ancestor, unless it has been secondarily lost in those species. Did consciousness first arise in humans, or in an earlier, nonhuman ancestor? If the latter, then what was this ancestor? Another possibility is that consciousness may have arisen multiple times, like winged flight, which evolved independently in insects, birds, bats, and pterosaurs. 