There is a lot of reading that can be done on the subject, and it is very interesting from an instrument making perspective as well. In one sense the bass came from the viol family and braced flat backs, outside rib linings, "gamba" corners, underhand bows and a few other physical characteristics scream viol. Other instruments with round backs, violin outlines and corners to name a few characteristics have definitely been influenced by the violin family, and you would be hard pressed to call them exclusively of violin family or viol family lineage.
As for construction changes/advances, those things are heavily tied to your first question of "where did it come from?" Depending on how far back you go or what you look at as a starting point, gut frets, 3-6 strings, tension pegs vs. tuning machines and their many variations, the evolution of the underhand bow and the invention of the overhand bow, the newer take on 3-5 strings, gut vs. synthetic vs. steel strings, methods of reaching low C or B, various tunings, change in neck angle to reflect higher tension, all the way up to things like removable necks/folding basses, the instrument has changed a lot, and continues to do so. The impact of those changes are not that easily defined, but they eliminated or significantly reduced many of the barriers and limitations of playing the instrument, and as a result the technical demands made of bassists are changing as well.
The Paul Brun book Joey mentioned is a fantastic resource, and it would be a disservice to write a paper about the history of double bass without using it as a resource. I agree with the good Dr. that citing forums and the information in them is not an easy thing to do, but there are good resources available. I am not sure of the length or depth of your assignment, but you may have to decide how far to go into the changing role of the double bass musically vs. its physical evolution.
Best of luck, and keep in mind there are plenty of people here who would enjoy reading it when you are done.