Why is that the prevailing civilization started on Eurasia ?

Jared Diamond highlights two major environmental advantages of Eurasia over other areas in which farming apparently developed independently. The various Eurasian inventors of farming, and especially those in "South West Asia" (roughly Mesopotamia and Turkey), had by far the best natural endowment of crops and of domesticable animals in the size range from goats or dogs upwards. The superiority in domesticable animals was the more notable, as other areas had at most two and often no such animals. Eurasia's other big advantage is that its mainly East-West axis provides a huge area with similar latitudes and therefore climates. As a result, it was far easier for migrating Eurasian populations to adapt those plants and animals to which they had become accustomed to new areas. By contrast the Americas' North-South axis forced migrating Native Americans to adopt new crops and, where available, animals as they migrated from North to South, because of the wide variation in climates.