Life talks

When I was in university, most conversations with friends were about university stuff: studying, boring subjects, impossible deadlines, weird lecturers, mad dashes from one building to another to make it to the next lecture, expensive food in the canteen, classes that went on till 22:00, anything and everything to do with our main occupation. Apart from that, we had conversations about hobbies and tv-series we were watching and the weird habits of our roommates, because we were still having time for hobbies and tv-series and living with random other people.
I have several friends who are still in university, and our conversations are generally about their world: university. This is a world we both know and can both relate to.
Then you get to the second 'step' in the conversational ladder: work. We are both working full-time, and several of our friends do too. These conversations are all about work: what we do, whether we like it, strange twists and turns in company policy, the quality of coffee in the pantries, conferences, weird co-workers and their weird habits, how much money we make, things that went very wrong, the joys and problems of office landscape, again; anything and everything to do with our main occupation. With friends that are still in university, you can't really have these conversations, because they've never experienced 'the working life' (or more accurately 'the office life'). The same is true for the next step on the conversational ladder, the step that I haven't yet taken but some of my co-workers have (and some of my acquaintances, which I haven't really spoken to since, as will become clear in a moment): children. Even though we share the same work environment, most of the non-work-related conversations I have with co-workers are about their children. What they eat (and don't eat), when they go to sleep, wake up, what funny things they did or said, what they're doing in daycare, what they're learning in school, what their teachers are like, what they did during the weekend, how much they like or hate their other siblings, anything and everything to do with their children.
Now I can't really participate in these conversations, because I don't have any children of my own. Somehow, this doesn't stop the subject from appearing or being discussed, even though my side of the conversation is only that of attentive listener with the occasional remark.
This made me wonder: why is it that I don't talk about work things with university friends, but that people with children do talk about their children with people who don't have them? Is it because children are considered such a universal topic that anyone must be interested and also have something to say on the subject? We all know children, we've all been one for a part of our lives, so the subject must be okay? Or is it that once you have children, there is no room in your life or in your head for anything else, and it is the only subject you can really express yourself on? Maybe I will find out when I get my own.

As always, there are exceptions to the rules above. I have several co-workers who refuse to talk about their children at work, stating it as 'un-professional'. They (generally men) talk about soccer, other sporting endeavours and tv-programs. Also, those co-workers with children who are older, secondary school or above, generally talk about films, cooking, books, or other generic topics.
And then there are the friends who do have a job and no children, but don't feel the need to talk about their work all the time. With these friends you can have in-depth conversations about travels or life plans or other major subjects, the things that you usually don't really get to with all the people mentioned above. These are the real conversations, with the real friends, with whom you can talk about the important stuff regardless of what life phase they or you are in.
But otherwise, conversationally speaking, I'm on the middle step. I do wonder whether I can still relate to my university-step friends when I get to the children-step. Only time will tell.