Why a Chimpanzee is not a monkey.

I hear a lot of people on the web or in daily conversation refer to almost any primate as a monkey, specifically I hear a lot of people refer to chimpanzees and gorillas as monkeys. I'm here to tell anybody that reads this that they're not monkeys. This blog post will thus discuss two questions; (1) What is a monkey? and (2) If not a monkey, what is a chimpanzee and a gorilla?

If you look at the picture above, you'll notice the Order that monkeys, chimpanzees, gorillas etc fall into is 'primates'. This is part of the Linnean classification system;

"Biologists classify life into a hierarchical family tree at the top of which animals that are similar to each other are grouped together. As you travel down the branches of the tree, so the organisms become more closely related.

At the top of the tree are the kingdoms - the major groups into which all living things are categorised - and at the bottom are individual species. Navigating from one of the major kingdoms listed below, and following through the groups, takes you on a journey through the evolutionary history of life." (BBC Nature).

 Strier (2000: 37) states that "there is no single trait that defines a primate or sets all of them apart from any other animals. Instead, there are trends in different suites of traits that appeared during the course of primate evolution and represent an overall primate pattern." Some overall primate traits she gives are:

1. Great mobility in our hands, feet and limbs.
2. Larger brain sizes than other mammals of a similar body size (Ibid).
3. Extended life history which Strier (2000: 43) argues may be related to our larger brain sizes. This leads to longer infant dependency and extensive socialisation and the formation of long-term relationships. Primates are altricial [born in an undeveloped state, requiring care], but humans are the most helpless of them all (Ibid).
4. Stereoscopic vision [forward facing eyes that causes the fields of vision to overlap which results in great depth perception]. We primates rely greatly on vision and have a reduced olfactory acuity, which is evident from the smaller snouts/noses on primates compared to our large, forward facing eyes (Ibid: 44).
5. Five digits on hands and feet, as well as nails instead of claws (Ibid: 45). And many primates, but not all, have opposable thumbs [a digit that can reach other fingers of the hand] (Ibid: 46).
6. The presence of a clavicle that aids in repositioning the upper body and gives the arm greater mobility.
7. Reduction in the number of teeth. The primitive form is around 40, for instance horses have around 40 teeth, while a lot of primates have 32 teeth, some have 36 (Ibid: 48-49).

Monkeys, chimpanzees and gorillas also all come under the suborder Anthropoidea, but then this is where it begins to differ. There are two types of monkeys; Old World Monkeys (OWM) and New World Monkeys (NWM). NWM are obviously from the New World and come under the infraorder Platyrrhini which refers to monkeys that "...are distinguished by having nostrils that are far apart and directed forwards or sideways, and typically have a prehensile tail [grasping tail]" (British Dictionary). Platyrrhini means 'flat nosed'. NWM have 36 teeth and are usually small and arboreal (Redmond 2008: 76). Examples of NWM are marmosets, capuchins, squirrel monkeys, sakis etc.

Old World Monkeys (OWM) on the other hand come under the infraorder Catarrhini, so too do chimpanzees and gorillas, but only OWM come under the superfamily Cercopithecoidea. Catarrhines "...are distinguished by having nostrils that are close together and directed downwards, and do not have a prehensile tail" (British Dictionary). All catarrhine primates have 32 teeth, but OWM have distinguishing bilophodont molars [the molars have 4 cusps arranged in 2 ridges] (Redmond 2008: 103). The OWM from the subfamily Cercopithecinae are cheek-pouched monkeys, they eat a wide range of foods, including meat, and are thus generalists. They also have ischial callosities [tough skin on their bottom]. Examples include baboons and macaques. The OWM from the subfamily Colobinae are specialists and eat leaves.

Thus primates not under these headings are not monkeys. Therefore lemurs, pottos, aye-ayes are not monkeys, they are strepsirhines, also prosimians, but are primates. Tarsiers are also prosimians but not strepsirhines, they are primates but not monkeys. Chimpanzees, gorillas, orangutans, bonobos, gibbons, siamangs and us [humans] are not monkeys either, we are primates and we are apes, gibbons and siamangs being lesser apes, the rest are great apes. Most apes are known for their large size, their intelligence and their lack of tail (Ibid: 146).

We can now answer the two questions posed at the beginning of this post. (1) A monkey is a type of primate. (2) Chimpanzees and gorillas are great apes.

So! What can you say when you see a chimpanzee, and don't want to call it a chimpanzee? You can say “OMG look at that ape! Isn’t she a beautiful specimen of the Pan troglodytes. My! What a wonderful primate!”

References [This list will only compose of the references that aren't linked in the text to the original source and also the British Dictionary, since my dictionary is an app]

1. Strier, K. B. (2000). Primate Behavioural Ecology: Third Edition. Pearson Education: Boston
2. Redmond, I. (2008). Primates of the World: The Amazing Diversity of our Closest Relatives. New Holland: London