Primate Taxonomic Groups

Some General Categories and Useful Vocabulary

Primates are the living species that are most closely related to humans. In class, I'll frequently refer to our primate cousins as monkeys, apes, or prosimians. These are not taxonomic groups because these terms are not part of the scientific classification we'll learn. However, the terms "monkey", "ape", and "prosimian" are commonly used by the public, and they are convenient short-hand for groups of primate species that share some physical and behavioral traits.

Prosimians are the most primitive primates. Remember, in the context of this class, "primitive" means "has ancestral traits". Prosimians are just as "evolved" as we are -- they have been evolving since the time of our last common ancestor, just like we have -- but they maintain more of the characteristics of our last common ancestor. Many prosimian species are small-bodied, insectivorous (they eat insects), nocturnal (they are active at night), and relatively small-brained. Prosimians you may be familiar with are lemurs, lorises, and tarsiers. Most live in Madagascar, where they don't have to compete with monkeys and apes, but some live on mainland Africa or Asia and avoid competition by being active at night.

Monkeys are larger-bodied than prosimians, in general. They have more derived traits, including a greater reliance on sight than smell and relatively larger brains than prosimians, and they are (almost all) diurnal (active during the day). Although some eat insects, many are frugivorous (they eat fruit) or folivorous (they eat leaves). Monkeys are very diverse. Some spend all their lives in trees; some spend much of their time on the ground. Some live in large colonies; some live alone. Monkey species you may know include spider monkeys, langurs, and macaques. Monkeys live throughout tropical Africa, Asia, and Central/South America.

Apes are the biggest primates, on average, both in body size and brain size. They are all diurnal and intelligent, but, as you'll learn, they're quite different in their adaptations. Apes include the gibbons and orangutans of Asia, as well as the gorillas, chimpanzees, and bonobos of Africa. You'll frequently hear people incorrectly referring to apes as monkeys. Curious George, for example, is clearly a chimpanzee and therefore an ape, but is always referred to as a monkey in the children's books.* Remember, Larry and Bob were right about this one. (Seriously, go ahead and watch. You'll never forget how to tell them apart.):

Scientific Classification or Taxonomy of Primates

As I said above, the terms "prosimian", "monkey", and "ape", aren't part of the modern scientific classfication system we will use in class. How do scientists classify primates?

Primates, including humans, are all members of the Order Primates (also the Kingdom Mammalia and the Phylum Chordata). Below is the taxonomy of the Order Primates. This does not include every taxonomic group of primates, but these are the ones we will learn about in this class.

These categories are not the same as "monkey", "ape", and "prosimian" because they reflect the evolutionary relationship between different groups of species. For example, a tarsier is a prosimian, but is in a different suborder than the other prosimians, like lemurs and lorises, because it is more closely related to monkeys. Similarly, Old World monkeys (like macaques) are in the parvorder with apes, to which they are closely related, rather than the parvorder of New World monkeys.

Each node of this tree represents one or more traits that distinguish the branches from each other. We'll discuss those traits as we work our way through the branches.

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*This came as a surprise to my children when they learned to read, since I always changed the word "monkey" to "ape" when I read it aloud to them.