I'm curious as to why several of you mention being surprised that co-workers have parents your age. I'm 43, and some of my youngest co-workers are in the early twenties, young enough for me technically to be their mother. Though I'll admit that I would be surprised too if they had parents my age, since the average age for a first birth is late twenties. But I'd pretty much expect that to be the case if I were ten years older.

Maybe it is the case that having kids (in my case kid) make you more aware of the passing of time. My son is very obviously a tall, lanky, moustachioed young man now, not a child, and I can visualize him having kids of his own even though I'm not expecting them anytime soon (dear god, no :-0). But I guess the awareness that I'm approaching grandmotherable age is kinda there, no matter how fit or active I am physically. And since I have grey hair too now people have stopped nagging me about having "another one" But I have close friends my own age or just a few years younger who want and are trying to have kids, so the very clear-cut generation divides aren't really there anymore.

But as to whether kids change an active lifestyle - it surely is harder to keep up a very active lifestyle once you have a child in the equation too, especially two, and school holidays are unfortunately limiting. I seriously missed not being able to travel when I wanted to, once I had a schoolchild. But I got a lot better at including physical activity in my everyday life, because that's where it had to be. Ok, so I didn't go to Antarctica, but I got pretty good at rock climbing, and biking everywhere, and I took up kayaking. And Antarctica is still there. I've met people who've said to us as young parents, as a compliment, "it's so nice to see that "life doesn't end" once you become a parent". And I thought "well, who told you it did in the first place?"