We are in no way separated by 40m years of evolution. Our common ancestor 'is'. That mouse you see today has been evolving just as long as you have, but with different priorities.

Our common ancestor 'is' what?

We are separated from mice by 80million years of evolution -- 40million from the common ancestor, and 40million to the other modern species.

Or simply 40million years of divergent evolution.

Technically yes, but practically the mouse reached a more or less standard form millions of years ago, in a local maximum, and we've been developing into all that we are mostly far more recently and represent a far more advanced form with lots of metrics (fitness to local environment is not the be all end all metric -- just the one evolution uses).

This isn't true for all species, it's (in a way) different depending on species. Your statement assumes that evolution is a constant, time-dependent process; it isn't.

For an example, I point to the horseshoe crab. We're separated by x million years of evolution from the horseshoe crab, because at some point there's a common ancestor. Its ancestor evolved to the horseshoe crab, millions of years ago, and then stopped. Meanwhile, our ancestor continued to evolve into us. The horseshoe crab is a prehistoric animal, a "living fossil". It hasn't evolved significantly in millions of years. This is quite different from mice.

Another example is the coelacanth fish; it was thought to be long-extinct as we have prehistoric fossils of it dating to the dinosaur days. Turns out it's still alive. Another less-extreme example is the shark: it's a little different than its prehistoric ancestors, but not much. I'm sure a biologist could point to a bunch of other species that haven't changed significantly since the days of the dinosaurs.

Mammals like mice have indeed been evolving just as long as we have, but many non-mammalian species have not.

Hello - I said "somewhat similar animals" by which I meant very early primates who were a bit like squirrels and mice. I should have made it a bit clearer!

I did get the date wrong - I should have said 65my.

Here is a link

http://www.smithsonianmag.com/science-nature/five-early-prim...

Good point. Separation can be even greater since each is 40M apart from a common ancestor.