I think some people are geared for it. Some people are not. Unfortunately, a lot of people that aren't geared for it still end up having children anyway and that becomes a huge mess, obviously.
I personally just don't like children. My family begs my wife and I to have children and it annoys us to no extent. We understand the complexities of having a child and we also understand how selfish we currently are. We would probably end up despising the child if we ever had one.
We go through periods at times where we'll see a baby and be like "aw, how cute", but that quickly changes when that child starts screaming and crying.
I can't even stand my nieces and nephews. I'm serious... I hate holidays because I know I'll have to put up with them. This sounds harsh, sure... but it's the truth. All I see out of them is a mass quantity of pure concentrated annoyance. While I love them because they are family, I simply don't want to be around them. If they ever needed help, I'd help them. If they ever needed a home, I'd house them... I'd be there for them because they're family and that's what family is there for... however, nobody said I had to like them!
Our views may change, obviously. As you get older, your priorities change and we both may have different opinions. However, we're both in our mid thirties and time is not on our side anymore and we still, to this day, feel that not having children was a great idea.
As far as the 51/49 split, I'd personally say I feel that way with my dog. :) However, when I want to get away from my dog, I crate her and go out to dinner!