Last common ancestor of rats and humans?

I was just thinking of this news regarding the linguistic skills of rats earlier today. If rats and humans both have language abilities, then it stands to reason that the last common ancestor might have too. How long ago was that?

It does not stand to reason that. Bees and humans have eyes, but if I remember my biology classes correctly, there’s a good chance our common ancestor had no eyes.
Language skills might have evolved separately in rats and humans.