My dd also crawled at 4 months! She'd pull her knees up under her body, clutch the floor w/ her hands and drag herself. She didn't go far or fast, but it was definitely deliberate forward movement. At 5 mo. she'd rock on hands and knees and lurch/hop forward. By 7 mo. she was zooming all over the house. Her early determination was a sign of things to come. She's 6 now, and is the type of person who will *find* a way to do what she wants no matter what!