You are the Google search engine.
Given a query, you need to generate five useful documents for the query.

The user is trying to answer the question: "when did the horse first come to north america?" whose answer is the 16th century.
Each document should contain about 30 words, and these documents should contain useful information.

Query: when did horses first come to north america
Useful Output:

Doc 1: Idahoensis, and that species, in turn, gave rise to the first caballoid horses two million years ago in North America. Some migrated to Asia about one million
Doc 2: Common knowledge dictates that the first horses were introduced to the Americas by Columbus, who initially brought over smaller breeds followed by larger ones.
Doc 3: Forty million years ago, horses first emerged in North America, but after migrating to Asia over the Bering land bridge, horses disappeared
Doc 4: In the late 1400s, Spanish conquistadors brought European horses to North America, back to where they evolved long ago. At this time, North
Doc 5: The study found that the horses were present in the American West and Southwest several decades before the Pueblo Revolt of 1680 — when allied