Why do the monsters in I Am Legend have super powers? When they hit the car with their heads they act like it was nothing. Or when the "alpha monster" hit the glass that Robert is inside, can he actuality break the glass like that?
How do they scale buildings so easily? What do they have that made this possible in such an easy way?
Why do they have that large jaw? My guess is because they use the mouth a lot, to scream, to bite, etc. But is that alone sufficient to explain this?