Then a better way to describe the "second wave" would probably be along the lines of "sailors have been spreading cats around the world since about 400 BCE". I

Then a better way to describe the "second wave" would probably be along the lines of "sailors have been spreading cats around the world since about 400 BCE". I think I've heard of islands that had no cats until they were visited by European ships in the 19th century, so it's a trend that likely didn't end until the whole world was colonized.