The Biological Classification of Humans

Humans have long recognized our similarities with the apes. Cultures with close contact with these animals often gave them names that reflect this similarity—such as orangutan, a Malay word that is translated as "person of the forest." The Greek naturalist Aristotle, whose 2,000-year-old writings form some of the basis for modern Western science, organized the living world into a linear chain from what he perceived as the lowest form to the highest forms and placed the great apes a step below humans.

As the modern scientific community was developing in the sixteenth and seventeenth centuries, a number of different methods for organizing biological diversity developed. Many of these classification systems grouped organisms by similarities in habitat, diet, or behavior; some of these classifications placed humans with the great apes, others did not.

Into the classification debate stepped Carolus Linnaeus, a Swedish physician and botanist. Linnaeus gave all species of organisms a two-part, or binomial, name in Latin, which was the common language of science at the time. These Latin names typically contained information about the species' traits—for instance, Acer saccarhum is Latin for "maple tree that produces sugar," the tree commonly known as the sugar maple, while Acer rubrum is Latin for "red maple."

In addition to the binomial naming system, Linnaeus developed a new way to organize living organisms according to shared physical similarities. His classification system was arranged hierarchically—organisms that shared many traits were placed in the same narrow classification, while those that shared fewer, broader traits, were placed in more comprehensive categories. The hierarchy took the following form, from broadest to narrowest groupings:

Kingdom

Phylum (or Division) Class

Order

Genus

Species

Thus, for example, all organisms that were able to move under their own power, at least for part of their lives, and relied on other organisms for food were placed in the Kingdom Animalia. Within that kingdom, all organisms with backbones (or another skeletal structure called a notochord) were placed in the same phylum, Chordata, and all chordates that possess fur and produce milk for their offspring were placed in the Class Mammalia, the mammals. Humans are mammals, as are dogs, lions, dolphins, and monkeys. The scientific name of a species contains information about its classification as well—for instance, humans, Homo sapiens, belong to the genus Homo.

Other scientists quickly adopted the logical and orderly Linnaean system of classification, and it became the standard practice for organizing biological diversity. Later scientists added a new level, family, placed between order and genus (Figure 8.6). Even more recently, biologists have added "sub" and "super" levels

Kingdom

(Animalia)

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