I REMEMBER going into the Saatchi gallery in London when it first opened and thinking how pretentious it all was. I walked around the gallery at the South Bank, unmoved and unimpressed by the pickled sharks and the unmade beds I found inside.

But a few days ago, I revisited it and came across a sculpture called Dead Dad, that made me stop and stare. The artist, Ron Mueck, had made an anatomically exact wax representation of his father, except it was shrunken to a pitiful three feet in length. I was startled to see the tiny man lying at my feet, with folds and wrinkles ornamenting his vulnerable waxen body.

At first glance it made me giggle, then laugh - his naked form looked comical and cartoonish when aged and shrunk to such a degree. He seemed like a character out of Viz with flaps of loose skin where a hearty paunch would once have been and giant bunions on his tiny, mangled feet. It was only when I looked harder that tears began to form in my eyes. In that shrunken, dishevelled form, I saw my own dad's transformation from the indomitable figure he was in his glory days to the fragile wreckage he has become. He went into hospital nearly a year ago and we thought he'd be out within weeks. But it is as if old age has hijacked his life plans and he now looks and acts like someone who has been defeated. The ageing process has been cruel and it surprises me even now that he can go from looking like a miraculously young 70-year-old to an old 102 in the space of a year.

He has diminished in height and his body has become minute and childlike. The only big thing on him is his eyes and overgrown eyebrows, which give him a slightly comical look. He is not happy to be old, and I think he feels short-changed at the positive pay-offs that old age is supposed to bring, when he'd rather have youth and immaturity above wisdom any day of the week.

We all comfort ourselves with the idea that as we grow older, wisdom and serenity compensate for our diminishing physical agility, and that the old have made their peace with the idea of dying. But seeing him grow older, weaker and madder, I am left questioning the assumption that all old people are happy to be wise, and don't mind dying as much as the young. Some, like my dad, rail against the crumbling body that has betrayed them, and would rather be partying like they're 21 if only their arthritis would let them.

There is nothing I can say or do to comfort my dad, because we both know that the thing that upsets him most cannot be remedied. So I sit and look at him lying on his bed, his ears big, his cheeks sunken and his shoulders rounded and frail, and I think of the universal human condition that is represented in Ron Mueck's funny old, tragic Dead Dad, and just like my dad, it makes me half-laugh, half-cry.