Here is an article with an interesting title:
Detection of hepatitis E virus antibodies among Cercopithecidae and Hominidae monkeys in Cameroon.
On PubMed: Modiyinji AF, Amougou AM, Monamele CG, Nola M, Njouom R. Detection of hepatitis E virus antibodies among Cercopithecidae and Hominidae monkeys in Cameroon. J Med Primatol. 2019;48(6):364-366.
A journal whose editors, I presume, know the difference between a monkey and an ape, has chosen to allow a title through that calls apes of the Hominidae family “monkeys“. This is interesting. Very interesting.
It has an impact factor of 0.6, and the few articles I’ve looked at, while not high level Nature stuff, are scientifically sound and worth reading. I don’t know how well or poorly the journal is considered in the zoological community.
Are apes monkeys?
The terms “ape” and “monkey” are not really scientific terms; they’re English terms and the supposed scientific difference came in with outdated classification systems that saw monkeys were smaller with tails and apes were bigger with no tails. There are not apes with tails, but there are tail-less monkeys such as the Barbary ape, which, by the way, is indeed a monkey and not an ape.
Likewise, “mole” is not a scientific term, but rather an English term for certain burrowing animals. There are at least two groups of animals called moles, which are completely unrelated to each other and look and behave similarly because they happened to evolve into similar looking creatures. This is called convergent evolution – unrelated animals evolved to share looks and behaviour. The Golden mole and the European mole are as unrelated as cats and mice. Therefore one cannot construct a single group of animals that contains only what we call “moles” in English.
Amongst the simians, there are 4-5 major groups we know today – New World monkeys, Old World monkeys, apes (great apes and lesser apes), and humans. Humans evolved from apes. Apes evolved from Old World monkeys. Old and New World monkeys evolved from a common ancestor monkey.
One position is that an animal that has evolved from a previous state is no longer necessarily classified as being part of the previous group. Therefore:
- Humans evolved from apes, but humans are not apes.
- Apes evolved from Old World monkeys, but apes are not Old World monkeys.
- Old World monkeys and New World monkeys evolved from a simian ancestor, but … wait, they ARE simians. They both belong to the infraorder Simiiformes, or simians. So do apes and humans! Now what?
- Humans belong to the infraorder Simiiformes, or simians.
- Apes belong to the infraorder Simiiformes, or simians.
- Old World monkeys belong to the infraorder Simiiformes, or simians.
- New World monkeys belong to the infraorder Simiiformes, or simians.
According to their scientific classification, all belong to the infraorder Simiiformes, or simians. So they’re all simians.
According to their English non-scientific classification, all are arbitrarily different things – humans or apes or monkeys but (usually) not more than one of these.
The English logic also breaks down when we come to the term “primate“. We ARE primates in English, and we ARE primates (order Primates) in science. Similarly we ARE mammals in English, and we ARE primates (class Mammalia) in science.
So, as you can see, how you classify us depends on whether you’re talking science or English.
Before we go on, please read the Wikipedia article on clades. I’ll use this term below to refer to “a group of organisms that consists of a common ancestor and all its lineal descendants, and represents a single “branch” on the ‘tree of life’“.
Above, where I discussed the two completely unrelated mole types, I noted that they could not be fitted into a group (clade) that contained only moles and contained all moles. Moles are not one group (clade).
With monkeys (simians = infraorder Simiiformes) it differs slightly. One can easily create a group (clade) that contains all monkeys – this is the infraorder Simiiformes. The problem comes in with the fact that one cannot create a group (clade) that contains ONLY monkeys. Simiiformes also contains apes and humans.
For the term “monkey” to be scientifically (taxonomically in this case) sound, it must have actual taxonomical meaning. “Monkey” must mean something. One must therefore be able to separate monkeys from everything else and put them in a single group that doesn’t contain other things. As can be seen above, one cannot do this. The smallest group (clade) that contains all monkeys also contains all apes and humans. One can create an artificial group that contains part of the simian group (Simiiformes), but it is not a real scientific group, only a partial group. Creating such a group (a non-clade) is not going to provide the term “monkey” with a taxonomically sound group of its own.
Taxonomically, if humans and apes are not monkeys, the term “monkey” is not a scientifically sound term.
Taxonomically, if “monkey” is to have any meaning, it must refer to a group that contains only monkeys, and the only way to form such a group called “monkey” is to include humans and apes.
If one rejects the above, then “monkey” is not a scientific term, but an English term only like “mole” or “mouse“. (Note that, apart from the genera Rattus and Mus, the distinction between a rat and a mouse is not a scientific/taxonomic one, but rather based on size.)
Are apes fish?
If one accepts the scientific use of the word “monkey” as I’ve described above, then there’s one additional step we must make. If that logic is sound, then the following logic is sound too:
For the term “fish” to be taxonomically sound, it must have actual meaning. “Fish” must mean something. One must therefore be able to separate fish from everything else and put them in a single group that doesn’t contain other things. But the smallest group that contains all fish also contains all apes and humans, as well as reptiles and birds. One can create an artificial group that contains part of the fishy group, but it is not a real scientific group, only a partial group. Creating such a group is not going to provide the term “fish” with a scientifically sound group of its own.
Therefore, if the term “fish” is to be used as a scientific taxonomical term for a single monophyletic clade, it must include humans. And whales. So whales are fish, even though they’re also mammals. Likewise, birds are dinosaurs, and both birds and dinosaurs are fish.
You decide if you want to use the term “monkey” (or “fish“) as a purely English term or a scientific classification.
Two concepts or one, based on linguistic background?
Leaving the language of science behind, we must ask whether language (“ape” and “monkey” as separate words in English vs combined like in Afrikaans “aap“) influences whether people conceptualise them as one or two groups of animals.
In modern English, we clearly have two words that refer to different types of primates – monkey and ape. So most English speaking people will have two separate concepts in their mind when they see the two words – monkey = smaller, has a tail; ape = bigger with no tail. A Barbary ape has no tail and is a monkey, not an ape. And many people consider baboons as separate things too.
Do people who speak a language that has only one word that includes all these animals, and who are not taught biology in English, consider these to be two separate types of animal (smaller with tails; larger with no tails), or do they consider them to be just one group with differences in size and tail that do not exclude them from the group?