Butterflies of American Horses Reaching the Old World?

[moxn]

Let's say the Pleistocene goes on normally outside of one detail: Horses never go extinct in the Americas, and eventually go on to be domesticated. Obviously this would have massive butterflies in the New World and essentially make it unrecognizable, but that's a thread for another day.

Instead, I'm wondering what changes would carry over to the Old World. Would things carry on exactly the same up until contact? Would there be climatic changes that could heavily affect them, or would this only lead to very subtle changes?

 

[moxn]

Bump. Has anyone done a topic on this before?

 

[The Gunslinger]

There were horses in the Americas and a lot of scholars think that early Native Americans exterminated them.

Bit butterflies in a world where the Aztecs have horses...

 

[moxn]

There were horses in the Americas and a lot of scholars think that early Native Americans exterminated them.

Bit butterflies in a world where the Aztecs have horses...

Well, for the purpose of the thread I'm assuming they aren't wiped out, for one reason or another. I know there's been a lot of threads on some of the affects in the Americas themselves, I'm just wondering if any of those butterflies would come across the Atlantic and affect the development of things there.

On a related note, what about vice versa? Would major changes in the Old World go on to affect the New before contact happened?

 

[Thesaurus Rex]

This timeline touches on this topic almost exactly.