A lot depends on where you draw the boundary for consciousness. Michael Pollan (in his new book, _A World Appears_) distinguishes simpler sentience from more advanced consciousness, and the requirements for sentience (be aware of sense data, have preferences, be able to respond to senses appropriately) are met by plants and single celled life (e.g. moving up a nutrient gradient). Recent findings in plant science are particularly mind blowing. Some are in Pollan's book, more are in _The Light Eaters_.