Maybe it didn't. Maybe it developed gradually over many generations. Indeed, many other animals exhibit some levels of consciousness.
Indeed, Junior. It seems that all forms of living beings possess some form of consciousness, be it simple sentience, awareness, all the way up to self-consciousness. Indeed, consciousness seems to be the hallmark of living beings. So perhaps the question then becomes: Did life "develop gradually?" If it developed, then it must have had a beginning -- Alamo-Girl and I have been referring to this as the inception of "life vs. non-life."
What do you think?