The columbian exchange irrevocably

homogenized the world's biological

landscape. what does john green mean by

this?

Ever since Columbus set foot in the Americas, the number of endemic species, that is to say, species that only live in a specific geographical area has diminished, while other species have thrived, in the five continents.

For example, the Columbian Exchange led to the cultivation of a South American crop: the potato, across Europe and Asia, where millions of people in cold climates where able to avoid famine by feeding themselves with it.

Another biological homogeneization process occurred with disease vectors: before the Columbian Exchange, diseases such as measles or smallpox were unheard of in the Americas. When Europeans arrived, Native Americans did not have defenses against this illnesses, and the majority of them perished because of contagion (over 90%).

Nowadays, these diseases are present all over the world, but thanks to vaccines, they do not kill as many people as before.

roosevelt believed that in light of the country's recent military successes, it was unnecessary to use force to achieve foreign policy goals, so long as the military could threaten force. this belief, and his strategy of “speaking softly and carrying a big stick,” shaped much of roosevelt's foreign policy.

social contract theory, nearly as old as philosophy itself, is the view that persons' moral and/or political obligations are dependent upon a contract or agreement among them to form the society in which they live