Paris, london, new york, and tokyo are all significant because
a. they are the most populated cities in the world
b. they are the largest cities in the world when measured in terms of area
c. they are global cities due to their influence in government, culture, and the world economy
d. they have the largest economic growth of all cities in the world

These cities are significant because they are global cities due to their influence in government, culture and the world economy - C.

It is not an understatement saying that these cities have drastically shaped the world economy, political scene, as well as the cultural scene. All of them played important roles here in the past and will probably play them in the future as well. 

Yes you are cute answer theories to explain the colonization of the new world the last great habitable landmass to be occupied by humans focus on the bering land bridge, or beringia, which emerge by siberia and alaska the last ice age.