What was the most significant of the effects of European contact with Native Americans?

introduction of disease.

Explanation:

The single greatest impact of European colonization on the North American environment was the introduction of diseases. Microbes of which native inhabitants had no immunity caused sickness and death everywhere Europeans went.

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herodotus taught this. herodotus was an ancient greek historian who was born in halicarnassus in the persian empire. he is known for having written the book the histories, a detailed record of his "inquiry" on the origins of the greco-persian wars.