Globalization and disease Eurasian diseases to the Americas was that many more native peoples were killed by disease and germs than by the colonists' use of guns or other weapons. Scholars estimate that over a period of four centuries, epidemic diseases wiped out as much as 90 percent of the American indigenous populations. In Europe during the age of exploration, diseases such as smallpox, measles and tuberculosis (TB) had already been introduced centuries before through trade with Asia and Africa. People had developed some antibodies to these and other diseases from the Eurasian continent. When the Europeans traveled to new lands, they carried
Mexican Americans an army to defend themselves from invading American forces after the Mexican army retreated from Alta California to defend other parts of Mexico. The Californios defeated an American force in Los Angeles on September 30, 1846. In turn, they were defeated after the Americans reinforced their forces in what is now southern California. Tens of thousands of miners and associated people arrived during the California Gold Rush, and their activities in some areas meant the end of the Californios' ranching lifestyle. Many of the English-speaking 49ers turned from mining to farming and moved, often illegally, onto land granted to Californios