ABSTRACT
This chapter charts a number of options for the evolution of consciousness (in a broad sense of that term) with particular attention to how consciousness fits into the genealogical relations between animals represented in the "tree of life". Animals originated something like 700-900 million years ago, and comprise a single tree-shaped branch within the total genealogical structure. It is still common, mostly outside of biology, to talk of "higher" and "lower" animals, and of a phylogenetic "scale". The chapter aims at a compromise between covering ideas that have been influential in the literature, exploring directions that are promising, and discussing options that illuminate evolutionary possibilities. It looks at a view based on a kind of overall cognitive complexity in animals, and then moves to views that posit more specific innovations. Evaluative feelings are plausible early forms of subjective experience. Perceptual states of some kinds are another plausible form.
