Another failed magazine snippet:

How old are you?

You may be surprised to learn that the person standing before you today didn’t exist eighteen months ago and bears only a passing resemblance to a person you met sometime in the past.

Nails hair and the surface of my skin is composed of dead tissue.   Blood and plasma cells live for about six months, soft tissue for approximately a year.  The cells making up bone live slightly longer, for up to eighteen months.  In fact, the only non-renewable tissue in the human body is in the brain.   When brain cells die they are absorbed by the body and the brain shrinks by an equivalent mass.   All the old tissue is absorbed and excreted or reused in a cannibalistic colony of cells that we know as a human body.   In fact, the only living tissue you can see, when you look at me, is my eyes.

So, if you haven’t seen me for eighteen months you are actually looking at a different person, one you have never met before.   Yet we recognise each other despite the changes; wrinkles witness that many cells occasionally replicate imperfectly.   As you and I grow older, all the cells in our body will stray from the perfection of youth, their original stem cells.   The process is known as ageing; it is why we only have a finite time on this earth and cannot live forever.   Each successive new cell becomes a little less like the original, each mutating slightly from the pattern until the body is no longer a viable colony capable of sustaining life.   The brain cells could live longer because they do not have to continually replicate, but even they cannot live forever.
 

Every time you get drunk, approximately a thousand (non-renewable) brain cells are destroyed – and the brain mass diminishes.

So, now you know why I hesitate, before answering, when asked how old I am…    How old are you?