Memory

I have been working my way through The Kinta Years by Janice Holt Giles (it was recommended to me by Morning's Minion) and I'm really enjoying it.  I had read a number of books by this author when I was growing up ( Johnny Osage, The Kentuckians), but I'd never read any of her autobiographical books.
This one is about her family moving to Kinta, Oklahoma when she was 4 and she talks about her earliest memories.  I was fascinated at the clarity of her memories from such an early age.  I have very few memories of my childhood and most of those begin when I was 8 or 9.  This is not a factor of old age, it's always been that way.  I use to ask my Mom if something happened to me or the family that wiped out most of my memories, but she'd laugh and say it was just an ordinary childhood.
I look at pictures of me at 4, 5, 6 and though I recognize myself I have no memory of the pictures being taken.
 I don't remember moving to Kansas City, MO when I was 3 and the trip took a couple of days and my Mom said I talked to everyone on the train, I don't remember my younger sister being born when I was a bit over 3 (my older sister who was 4 1/2 at the time says she remembers it well), I don't remember starting Kindergarten (who forgets their first day of school?), I don't remember First Grade, the move to Oklahoma, Second Grade or the move back to California the year I was 7.
I remember the house we rented when we went back, some friends from that time and my paternal Grandmother Lola.  But I don't remember ever having seen her before, though I had.
How strange.  Mac says he remembers laying in his crib and his Mother picking him up.
Am I the only one whose memory doesn't go back to very early childhood?