Nope. It's not an either/or scenario. You can have both, though there will be times when one takes priority over the other (for fathers as well). The only intensively time-consuming part of childhood is when they're really little, and that's just a tiny fraction of your life. I was working when my first was born, and an international move required a job change for me. I have a background in physics and left my job in the US as a spacecraft controller to make the move. Instead of seeking new employment, I opted to stay home with my baby, especially since we were planning for another, and I knew that there would be only one shot to spend their formative years with them. Now that they're in school, I've decided to do a PhD, which will be awarded next year. I loved staying home with them before, and I love what I'm doing now, and that's what's important. It doesn't have to be career or kids; it can be both. Sure, I won't be winning any Nobel prizes, but that's not what I was seeking to begin with. I'm happy with the contributions I'm making with my research, and I'm happy with my life. Really, that's all that matters.