I never crawled. My parents were worried, they went to doctors who assured them that I was mostly alright, and then one day, I got up and started walking.

I saw the exact same behavior with my ex-gf's sister's son, who we took in after he was in foster care from birth. The child had clearly not been engaged with properly... the back of his head was bald because he was always on his back in a cramped bassinette and at 11 months he hadn't even learned to turn over. Within 3 months of being with us, he was walking.