While the exact origin of consciousness is debatable, and polarized on a mammalian time-chart, the fact that all mammalian creatures acquired consciousness as a datum, that is, as a fixed starting point in our brains, is not.The history of these living, yet mortal, creatures is documented by their fossils that are preserved in sedimentary layers over geologic time, where we can see (read) the small patterns to help understand the big picture, and that, is the progression of evolution. Yet, there are at least two types of mammalian evolution.
The first and most obvious is the aforesaid fossil record. That record, despite gaps, is of such an exacting nature that it is no longer considered a theory of evolution, but the established fact of evolution.