That's what I mean. It's evolution, but it isn't necessarily "progress". It just works for Chihuahuas for now, because they are human symbionts, and as such, are more likely to be found in human habitats than big ol' wolfdogs (though there is one in my neighbourhood, lovely fellow.)

But take away the humans, and chihuahuas will have to compete with actual rats in order to survive, and will probably lose.

You also have mental evolution, but that's pretty much invisible unless you see the behavioural changes happening (see the difference between urban and rural raccoons.)

That's what I mean. It's evolution, but it isn't necessarily "progress". It just works for Chihuahuas for now, because they are human symbionts, and as such, are more likely to be found in human habitats than big ol' wolfdogs (though there is one in my neighbourhood, lovely fellow.)

But take away the humans, and chihuahuas will have to compete with actual rats in order to survive, and will probably lose.