My earliest memory is from when I broke my arm in kindergarten. I believe it was spring, so I was probably 6? It's the only time I've ever broken a bone, which makes it pretty significant. I'm not sure I'm the same person as I was. The "Me" of today wouldn't have tried playing with my older brothers (which led to the broken arm) at all.
My earliest memory is the only time I remember seeing my dad shave off his beard. I think the memories being unique occurances of some important event make them much more distinct in our memory.
