My kids are just really different...I do think it's hard to look at the early end of the spectrum and make assumptions. Easier to look backwards after one has been identified as advanced or gifted.
My DS did not talk much until he was about 2.5...but he knew all his letters at 2 and started reading about the same time her started talking. He was average with crawling, sitting, walking...nothing special or behind. He could hold a pencil and utensil very early though, and we knew he was left-handed well before his first birthday.
My DD, OTOH, did most 'classic' milestones early: smiled early, sat up early, crawled early, walked early...even pretty much skipped baby food and went right to table food (attributed this to bigger brother). She also started talking very early and was speaking in well-developed sentences by 15 months. Now at 2, she doesn't know a single letter like DS or read a single word...but she can count well over 20 and can do puzzles amazingly.
I have chalked up some of the differences we've seen to gender (maybe erroneously so). I guess it remains to be seen if my DD has the drive to learn and ability to synthesize information quickly the way her older brother does.
