New Theory Explains How Consciousness Evolved -- It Arose as a Solution

Princeton University neuroscientist Michael Graziano's piece in The Atlantic on how consciousness evolved has a strange beginning:

Ever since Charles Darwin published On the Origin of Species in 1859, evolution has been the grand unifying theory of biology. Yet one of our most important biological traits, consciousness, is rarely studied in the context of evolution.

Perhaps it's just me, but how can evolution be the grand unifying theory of biology if it doesn't explain one of the most impor...