Cohabitation? You actually have non-human species living in the same place as humans! That's brilliant!
Non-humans are just discovering us at the moment. And many of them try to take over the world. I work for a group that defends the earth against them, but I traveled with a man who always took the peaceful approach when he could. So I'm trying to turn things over in the organization as best I can.
[Martha's age isn't too scary, minus the part where she sort of has to make it up because she's not quite sure how to count it. Time alive or chronological according to the year it is. And she's also not fully positive how long she traveled with the Doctor.]