Travel Around the World Has Gotten a Lot Easier in the Past

Travel around the world has gotten a lot easier in the past century. It has become very common for immigrants to move to new areas, establish lives in regions other than where they were born, and find spouses in new regions. What, if any, changes to genetic diversity between populations will be the likely result of changes in mobility of humans?

A) The number of differences among human populations will decrease.
B) The number of differences among human populations will increase.
C) The number of differences among human populations will stay the same.