Answer: The different shapes of the two Continents.
Step-by-step explanation:
Professor Jared Diamond does not attribute the technological might of the Euro - Asian cultures over the American cultures to intellectual prowess. He rather attributes it to the geography of the Euro - Asian lands which had similar latitudes. Therefore, when technologies where developed they could spread faster and with more ease.
Whereas, countries in the American continents did not have stable climates and similar latitudes to aid the spread of technologies from one place to another. He gave an example of the gunpowder developed by the Chinese which could travel more than 6000 miles within a short time while The wheel developed by the Mexicans could only travel 500 miles.