Changes

===Colombian Exchange===

===Colombian Exchange===

[[Colombian Exchange]]. The almost total isolation of the Western and Eastern hemispheres meant that when Christopher Columbus initiated travel back and forth, new and devastating germs traveled along. Far more Europeans traveled the ships, so the disease flow was primarily from east to west. The native populations of the Western Hemisphere were especially vulnerable to the new diseases of smallpox and measles. The Indians had not built up immunity over the centuries, and so the death toll was horrific. In the territory that became the United States, the population of many tribes fell 75 to 90%, and many tribes vanished all together.  

See [[Columbian Exchange]].  

 

The almost total isolation of the Western and Eastern hemispheres meant that when [[Christopher Columbus]] in 1492 initiated travel back and forth, new and devastating germs traveled along. Far more Europeans traveled the ships, so the disease flow was primarily from east to west. The native populations of the Western Hemisphere were especially vulnerable to the new diseases of smallpox and measles. The Indians had not built up immunity over the centuries, and so the death toll was horrific. In the territory that became the United States, the population of many tribes fell 75 to 90%, and many tribes vanished all together.

===Industrial Revolution to present===

===Industrial Revolution to present===