Why is it so important to find a more complete skull of Australopithecus afarensis?

Watch the following video on the discovery of Australopithecus afarensis:

https://www.youtube.com/watch?v=PR_9_5gxvxg

(The video is about an hour.  The sound will get funky for a couple of minutes, but hang in there — it clears up.)  As you watch, take notes and answer the following questions:  In the 1970s, what did paleoanthropologists hypothesize the earliest hominins would look like?  How did Donald Johanson’s discovery change the paradigm about early hominins?  Why is it so important to find a more complete skull of Australopithecus afarensis?