Why did the Mound Builders migrate to the Central America?

Directions: Read the following passage and answer the question that follows.

In various parts of the continent, remains are found of the people who settled the country in prehistoric times. Through the Mississippi Valley, from the Lakes to the Gulf, extends a succession of defensive earthworks. Similar ruins are found in various other sections of the United States.

The largest forest trees are often found growing upon them. The Indians have no tradition as to the origin of these structures. They generally crown steep hills, and consist of embankments, ditches, etc. indicating considerable acquaintance with military science. At Newark, Ohio, afortification exists which covers an area of more than two miles square, and has over two miles of embankment from two to twenty feet high.

Mounds, seemingly constructed as great altars for religious purposes or as monuments, are also numerous. One, opposite St. Louis, covers eight acres of ground, and is ninety feet high. There are said to be 10,000 of these mounds in Ohio alone.

A peculiar kind of earthwork has the outline of gigantic men or animals. An embankment in Adams County, Ohio, represents very accurately a serpent 1000 feet long. Its body winds with graceful curves, and in its wide-extended jaws lies a figure which the animal seems about to swallow. In Mexico and Peru, still more wonderful remains have been discovered. They consist not alone of defensive works, altars, and monuments, but of idols, ruined temples, ducts carrying water, bridges, and paved roads.

The Mound Builders is the name given to the people who erected the mounds of North America. They seem to have emigrated to Central America, and have developed a high civilisation. They built cities, wove cotton, worked in gold, silver, and copper mines, laboured in the fields, and had regular governments.