All right, messing around with the islands and continents of earth is not really much of a challenge, I'll admit. Where the challenge does come in is not accidentally butterflying away humanity-so messing with Africa is definitely out, and this probably means that dramatically altering at least the western half of Eurasia and Arabia is also out. That leaves Antarctica, Australia, and North America as continents to mess with. And of course, with all those Pacific and Indian Ocean islands, humanity probably won't notice an archipelago more or less. Obviously, this does stray into ASB territory, but if there are any geologists out there, I would like to hear your opinion as to exactly how outlandish it is to alter Earth's landmass while still allowing Homo sapiens sapiens to exist. Is it totally ASB, or just a little bit?
So, what are your thoughts? Americas that never connected? An Australian continent that did connect to the Asian continent? A more southern Hawaii that provided a stepping stone for a more successful Polynesian settlement of the Americas? A portion of Western North America that separates from the continent a la Madagascar?
Harry Turtledove has already explored this with a dry Mediterranean and an Eastern North American Madagascar (the "Atlantis" series). I'd be interested to hear your thoughts.