Do you mean what? I would say disease, the natives have never came in contact with those sicknesses so they died out fast because of how weak their immune systems were.
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<h3>The us treated Cuba like dirt</h3>
<span>Various barbarian groups weakened the empire with a series of invasions. </span>
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People with type O- blood are called universal donors because their donated red blood cells have no A, B or Rh antigens and can therefore be safely given to people of any blood group. ... Their plasma does not contain A or B antibodies and can be transfused safely to all blood types.
