Ancient mother

Aidan (singing): It was a night like this,40 million years ago....
Me (singing): ...when your mother was born!
A: Really?
M: What?
A: You were born 40 million years ago?
M: What do you think?
A: Ummmm....yes!
M: Not quite! How old am I?
A: Ummmmm. Thirty......
M: Yes, thirty....how old is Isabelle?
A: Seven!
M: So I'm....
A: Twenty seven.
M: Thirties remember.
A: Seventy three.
M: Other way around.
A: Thirty seven!
M: Yes!

(It was Walk the Dinosaur, Was (Not Was) - original version. I wonder if Aidan is a visual learner - his response to my questions implies he was seeing the numbers in his head).

Oh I just remembered that this is an extra special birthday for suburban neurosis!