My earliest memory is being in a crib, looking up at the ceiling, and being overwhelmed with claustrophobia. I also remember other things, like riding my toy truck into a crater in the middle of the road.
But do I really remember events from several decades ago, or do I just remember remembering? At age four you remember what happened at age two, but at age six, do you still remember what happened at age two or rather do you remember the much more recent remembering of what happened at age two. So by the time you’re in your thirties thinking you remember your toddler years, you’re just remembering a remembering of a remembering etc. Perhaps each memory of an event is like a xerox copy of the last time you remembered that event and so the quality decays each time and perhaps you only have so much time to remember the event (or remember its memory) before it’s lost forever.
Did I just come up with a new theory of long-term memory that will revolutionize cognitive science? Doubt it. Someone else probably though of it first.