How does latitude (north-south axis) and longitude (east-west axis) play a factor in the development of the Americas vs. Eurasia?

makes
the claim that because Eurasia is on the east-west access, its people live at a similar climate
range, adapt to similar diseases, and can therefore develop in conjunction with one another. For
example, take the River Valley Civilizations. Mesopotamia, Egypt, and the Indus Valley
city-states all developed similarly and were able to trade. When diseases passed from one to the
next, survivors were able to build immunities which would be passed on through genetics and
future trades. Not all civilizations were able to trade, as some like Shang China were
geographically isolated, but the basic premise of Diamonds argument is that the east-west nature
of Eurasia allowed for similar human development.

For the Americas, which are
on a north-south axis, Diamond argues that development happens differently because people exist
in different climate zones. Whereas much of Eurasia is temperate, only part of the Americas is
temperate. This diversity in climate causes different development. Diamond argues that this
geographic determinism helps explain why American civilizations developed in greater isolation
than her Eurasian counterparts and why American civilizations did not share cultures, germs, or
advancements in the same way.