Different levels of consciousness The answer provided by @user287279 to  When does a human baby develop a consciousness? is a great answer in my mind which scrapes the surface of what consciousness consists of.
When you look at consciousness and how there are different levels to it, I couldn't initially think of any lower level of consciousness other than described in the answer:

the ability to sense the world around you in an independent way

But there is the preconscious, where information is available for cognitive processing, but lies outside conscious awareness.
Dehaene, et al. (2006) provides a good rundown on the difference between conscious, preconscious and subliminal processing, along with possible reasons why some knowledge remains permanently inaccessible; however, it doesn't indicate when preconscious processing begins.
I wonder if there is any scientific argument where it is considered that preconsciousness could have started earlier than consciousness?
References
Dehaene, S., Changeux, J. P., Naccache, L., Sackur, J., &amp; Sergent, C. (2006). Conscious, preconscious, and subliminal processing: a testable taxonomy. Trends in cognitive sciences, 10(5), 204-211. doi: 10.1016/j.tics.2006.03.007Free PDF available at: https://www.researchgate.net/profile/Claire_Sergent/publication/7177242_Conscious_preconscious_and_subliminal_processing_A_testable_taxonomy/links/5a09ad5a458515afc7b0e2b3/Conscious-preconscious-and-subliminal-processing-A-testable-taxonomy.pdf
Preconciousness is associated with intense activation, yet confined to sensori-motor processors ; 
 Occipito-temporal loops and local synchrony ; 
 Priming at multiple levels ; 
 No reportability while attention is occupied elsewhere ;

quora could also provide some answers : https://www.quora.com/What-is-the-core-of-human-consciousness/answer/Daisi-Lui ;

preconsciousness could have started earlier than consciousness ;

Freud, S., Strachey, J., In Freud, A., In Rothgeb, C. L., Richards, A., &amp; Scientific Literature Corporation. (1953). The standard edition of the complete psychological works of Sigmund Freud.