That said, some of Jared Diamond's arguments are really lame.. just poorly thought out. For instance, is claim that the use of wheels for transportation is in some way gated by the availability of pack animals. This guy has never used a wheel barrow I guess... of course he has and mentions them much later in his book, but dismissing the point as a "puzzling non-invention". This realization doesn't seem to have him question his earlier assertion that wheels for transportation would only be invented where pack animals are available.
I think it's got nothing to do with pack animals, and the truth is that wheelbarrows, and wheels for transportation generally, are one of those inventions that are obvious only in retrospect. Even after you've invented wheels on toys, it isn't necessarily immediately obvious that wheels could have practical applications as well. A very small handful of people in the history of humanity had this idea and most people never did (and just copied it from other people). It's not because of geography or ecology, just shear dumb luck.