Which of the following best describes Alfred Crosby's argument in the passage above? A
Various Amerindian groups did not have contact with each other before 1492
B
Amerindians' long isolation Yrom the rest of the world had placed them at a biological disadvantage.
с
The genetic makeup of the native population of the Americas remained unchanged until 1492
D
By 1492 Amerindians generally had migrated for shorter distances than had other groups