I've just finished McCann's 1491 and on to 1493, about pre- and post-Columbian Exchange, respectively. Something that stood out was the commentary on why Americ

I've just finished McCann's 1491 and on to 1493, about pre- and post-Columbian Exchange, respectively. Something that stood out was the commentary on why Americans never invented the wheel (given they independently invented agriculture and government)... and the answer was exactly that; terrain. Plus lack of horses... when you have llamas instead, you build your empire's "roads" for walking, not for carriages.