Eurasians were all on that one big east-west-oriented land mass, so why did the west go "west" and the east go "east"?

Good question, Mary. I wondered what might have made traversing the Himalayas more appealing to the Buddhist monks from India than migrating the other way via the Hindu Kush and rugged lands that are now Afghanistan and Pakistan. Either way they would hit high mountains, dry steppes and certain danger from unfriendly locals, wolves, tigers and snow leopards.