I would go further than this: It is absurd to assert that we know they had no contact with each other. Archaeology is full of occasional one-off weird shit from one civilization randomly being found in some other civilization thousands of miles away that it had no business having contact with. And yet, there it is.

A lot of scientists see the breadth and the rigor of the models that they follow, and they make the understandable but wrong leap into saying “this thing isn’t in my model, so that means it is definitely not true (even though there’s no particular negative evidence), because if it were, it would be in my model.”

I have no way of being sure, any more than they have any way of being sure in the other direction, but I think the sudden appearance of farming at basically the same time the world over is explained by exactly the explanation that it seems like it would be explained by. All it takes is one.