As a kid, I remember being fascinated by the idea that all my cells regularly die and get replaced over an interval of several years, that at age 10 my body was all different from the body I was born with: what did this mean about who I was? We know even more about cell turnover now - I just looked up human cell longevity, and studies using modern cell dating techniques  show that the cells in our body average about seven years of age (except for most brain cells, which survive our whole lives with stable wirings, perhaps answering my question of my identity also being stable, I guess).
Everyone knows that feeling of getting together with friends whom you haven’t seen for years and being bowled over by how different their kids are from the last time you saw them. The kind of change kids do is so total, obvious, and all-encompassing. Many times I have remarked how interesting it is to have kids to mark the passage of time, because us adults seem so static; indeed I’ve taken comfort at reunions with long lost friends and family in the idea that we have changed little since we were last together - that we can just pick up on our friendship where we left off the last time.
As comforting as this nostalgic idea is, it isn’t really true - of course I’ve changed, not only turning over most of my cells, but also to some degree my identity and personality. I’m not compatible with some friends with whom I jibed with well in the past. Looking back over my life-changing events of the past 10 years how could I not have changed - I finished 30 years of being a student, I left a travelled road to develop a non-traditional career, I mothered two children (just their change is enough to profoundly change me), and moved my household twice, one of these times across the country. But it takes some thinking back to remember who I was 10 years ago - my recollections of me minus 10 years are spotty, fleeting, and my recollections themselves probably change regularly too, so quantifying how much I’ve changed is hard to do. My mom has kept a diary of her life, writing an entry for every day, since she was 20 years old and has more than 50 journals lining her bedroom bookshelf. In here is a memory bank - a time capsule - not only of my mom but also of who I was in the past (as a mother myself I am assured that much of the content of these books concerns my brother and myself). I haven’t read any of these journals (and my mom hasn’t either, she says). But maybe one day I’ll read through this independent analysis of the changes in my life and in me, through the eyes of someone else. That would be interesting. A little freaky, though, I think.
My line of thinking here was set off by an NPR article  I heard two weeks ago that has haunted me since. It cites research from a psychology study published in Science magazine indicating that while we recognize change in our pasts, people generally perceive themselves as having achieved their final personality in current time, and do not anticipating changing as they grow older. One of the researchers was quoted giving possible reasons for why we don’t anticipating being different in the future: “it's just really, really hard to imagine a different, future version of yourself. Or maybe people just like themselves the way they are now, and don't like the idea of some unknown change to come.” I think these are both true.
For me, my future self is dependent not only on the changes that happen directly to me, but also the changes on those people around me who influence and imprint my life - for I think what has made the biggest changes in my life are relationships with and influences of particular people. So making predictions of future change does get complicated very quickly. I don’t particularly like the idea that in the future I’ll leave behind some of the things, ideas and people that may be very important in my life now, replacing them with newly important future things. But I guess leaving behind these things will happen naturally, and even if difficult will become easier over time, and I’ll have patchy memories of much that is the crux of my existence now, instead I will be filled with the evolved thoughts and passions that will make up the me of the future. Amazing how much happens in a lifetime.