Did the colonists define the Native Americans as being of a different race?
During the 1700s, the same time period colonization in North America was at its greatest height, scientific advancements were being made in classification. It can be said that these systems of classification helped feed the idea that people are of different and even superior or inferior races, an idea the British colonists brought with them as they settled in North America and encountered Native Americans (American Anthropological Association, Race, "The Story of Race Transcript").
In 1758, a European scientist named Carolus Linneaus published his book titled Systemaa Naturae in which he built a classification system. Using his classification system, he broke all of nature down into the animal kingdom, the plant kingdom, and the mineral kingdom. Particularly influential in developing the ideas of race distinctions was his classification distinguishing Homo sapiens from the rest of the animal kingdom. Besides separating humans from other animals, Linneaus also classified seven different human races based on physical characteristics and even personality traits, described as follows:
...the white Europaeus was "sanguine" and "muscular"; the sallow Asiaticus was "melancholy" and "stiff"; the red Americanus was "choleric" and "upright"; the black Afer was "phlegmatic" and "relaxed"; the wild and hirsute Ferus ran about on all fours; and what could not be classified otherwise (such as giants and genetic mutants) was relegated to the category of the Monstrous. (as cited in University of Pennsylvania, "Contexts--Science--Physical Anthropology")
Linneaus's race classification system was widely influential, even influencing such important figures as slave owner Thomas Jefferson, who saw a significant biological distinction between races that established social superiority.
Hence, we can certainly say that the North American colonists viewed the Native Americans as being of a different and even inferior race due in part to the European scientific classification system.