why can’t great apes speak?

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This haunts me. Gorillas and chimps are crazy smart and can be taught sign language, so why can’t they speak? They have human-like mouths and they’re obviously vocal, so why don’t they at least have the vocabulary of a toddler?

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Anonymous 0 Comments

Eh, some apes have been taught to communicate using sign language signs but they haven’t necessarily acquired *language*. Vocabulary? Sure. And they have even shown an understanding of quite complex ideas and concepts – even humour and jokes. But that’s not language. They haven’t shown an aptitude for grammar, for example. In the least offensive way possible, they’re sort of on par with older feral children who weren’t able to acquire language either – like Jeanie, a famous and extensively studied feral child who learned vocabulary and concepts, but couldn’t acquire grammar and language.

Both of them would say things like “love baby doll it” or “I cat eat bread”. A clear attempt at communication, but mostly just a jumble of words *just* shy of structure and language.

Which, to the point, isn’t all that different from a toddler. They might even have a vocabulary on par with a toddler. They’re just missing the brain power or exposure (in the case of feral children) to make it *language*.

As for why they can’t speak, it’s more likely that they just don’t. Either because they’re simply disinclined (like how some birds are *excellent* mimics and some birds can’t be arsed. It’s a natural inclination of some but not others) or because their brains just aren’t capable of making the connection. Scientists used to think they physically weren’t capable – that, structurally, they couldnt produce the sounds if they wanted to. But more recent studies have found evidence that, based on their anatomy, they probably could produce language sounds. The precise reason they don’t, however, is likely that they just can’t grasp language like a human brain can.

Anonymous 0 Comments

I wrote this up about a year ago, and I’ll post it again

Chimpanzee and Bonobo vocal chords/tracts are capable of producing human speech. The reasons that they do not speak are not because they are physically incapable of doing it. When scientists used computers to model the vocal tract of chimpanzees, the computer models demonstrated that the issue with chimpanzees isn’t that the vocal tracts don’t work to produce human speech. [Here](https://www.youtube.com/watch?v=Hq0H1kEFNAk&feature=youtu.be) is an example of simulated macaque vocal chords producing human speech. (Warning: This is pretty spooky since its computer generated)

In fact, it turns out that chimpanzees, like the vast majority of other animals, can’t learn new sounds at all, and that’s why they cannot speak; teaching chimpanzees/bonobos gestural communication works a lot better than trying to teach them to talk. Many chimpanzees/bonobos like Washoe, Nim, and Kanzi have successfully learned a few hundred words in sign language, but they can’t learn spoken language since they never learn to produce new sounds– the only species that can do this to my knowledge are humans, many species of birds, dolphins, elephants, seals and bats. (I’ve been corrected about this multiple times and have edited in the better info. I don’t know if it’s good form to credit the people who told me this or not)

I can’t really speak for songbirds, but **the reasons why humans are able to produce speech are deeply ingrained in the human brain**. What I mean by this is that it’s not just a blanket “we’re smarter than chimpanzees, so we can speak”.

Individuals who suffer from microcephaly often have brains about the same size as chimpanzees, but every one of these individuals, while they often have speech problems, are better at language than even the smartest chimp. The reason that we’re able to speak and that other animals can’t is because our brains are wired differently.

To be able to understand this, you have to be able to understand kind of the basics of human speech production.

Neurologists have figured out that if you damage the posterior of an area of the brain called the superior temporal gyrus on the left side of the brain in humans, they become unable to comprehend speech. This area is called Wernicke’s area, and is thought to be strongly implicated in speech comprehension.

Wernicke’s area has a really strong connection to a region in the frontal lobe of the brain that, when damaged, causes individuals to no longer be able to produce speech. This area, named Broca’s area, is strongly implicated in speech production.

The neuronal tract between Wernicke’s and Broca’s area is called the arcuate fasciculus. Damage to it causes individuals to become unable to repeat words. IE, they can process the word in Wernicke’s area, but they cannot get the information to Broca’s area to be repeated. Wernicke’s area also has projections to areas around it that are thought to be involved in other aspects of language like grammar.

So when asking about why humans can talk and why other primates can’t, you have to look at Wernicke’s and Broca’s area. Macaques actually have fairly well developed Wernicke’s areas, and are thought to be involved in functional reference calling. Functional reference describes how macaques give different warning calls based on what kind of predator it sees. So, for example, a macaque gives a different call when it sees an eagle vs when it sees a leopard. Damaging a macaque’s Wernicke’s area will prevent it from comprehending these functional reference calls.

*However*, damaging a macaque’s Broca’s area will **not** interfere with its ability to make any calls at all. This supports the finding that functional reference calls are actually involuntary. They just don’t have the area of the brain dedicated to producing speech like we do.

Neurons in the brain are clustered into units called “cortical columns”. The individual cortical columns between humans and chimpanzees are about the same, except in two area. In Wernicke’s area, humans have much thicker cortical columns than chimpanzees do, suggesting that, in a simplified explanation, that humans dedicate more “brain power” to speech comprehension than chimpanzees do. The same is true for Broca’s area, and on top of that, a human’s Broca’s area is also much larger than a chimpanzees.

Additionally, brain imaging studies have shown that the human arcuate fasciculus, as well as the connections between Wernicke’s area and the other semantic areas around it, are incredibly more developed than in other species. [Here](https://imgur.com/a/wgA4F) is a schematic for the differences between them. As you can see, the connections are very weak in macaques, slightly stronger in chimps, but much, much stronger in humans.

So the question as to why primates are incapable of speech kind of boils down to the fact they don’t really have the brain connections needed to produce speech or to be able to put together the individual words needed for language to make meaning.

Additionally, Broca’s area is not just involved in “generating words to say” but also involved in the motor aspects of speech. In this way, it is true that chimpanzees do not have the neurons needed to make control their throats and mouth enough to produce speech.

But why exactly do our brains develop differently like this? This is a tough question to answer, and it will require a much greater knowledge neurodevelopment than we do now. However, one interesting finding is the FOXP2 gene. I don’t know too much about it, but the FOXP2 gene is a regulator gene that controls the expression of other genes. Additionally mutations in the FOXP2 gene cause movement disorders in the mouth and face, and disrupts the production of speech. Individuals with a mutation also have smaller Broca’s areas. Very interestingly, our FOXP2 protein is distinctly different from those of almost all other primates, who have very similar FOXP2.’

**Edit: Another copy and paste**

The target audience of this response obviously isn’t literal 5 year olds. One of my pet peeves is that people who write on ELI5 often have no idea what they are talking about, and simplify their answers to the point of uselessness. My goal was to write a response that took a bit of effort to read, but would be as complete and accessible as I could make it. The diction, tone, and length of this post were all written with a casual audience in mind. If you’re confused by anything, I am more than happy to elaborate– I wrote this to hopefully help people learn something about neuroscience, not to seem smart, so if I slipped up and got too technical somewhere, just let me know. I am happy to edit my post.

Anonymous 0 Comments

>can be taught sign language

Not one of them has ever used sign language to ask a question.

Anonymous 0 Comments

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Anonymous 0 Comments

It is coded in your DNA how you get built from just an egg. It contains info to make a whole new living being. However as you are coded in a way that you will be a being that talks, you have that tools avaliable to you in that code and will eventually have that tools in final build. It is really similiar to building a computer. Lets say you were an android in human form; to be able to speak first you need phsical tools for that such as tongue, cords, lungs etc. Then you will need what we can call the hardware. In our brains; we don’t start with perfect software(driver) for many things but we get to have hardware(sound card) that allows it to be used to start with. It is such a neat way because we create our own software based on our own hardware. Our senses gather informations which we are not familiar with at first such as sound, noises, light etc. then in time we learn to give them meaning and finally create a software that effectively hears, sees etc. This way we get to have a custom made driver for our own system and even if we would be different from other humans, we get to have a nice working set up since its custom made for each of us. If that wasn’t the case and we started with an inbuild software then any difference in our build could make our software have troubles. Here comes to your answer, even with brain power equals to us, without our tools, apes may still not be able to speak as we do since they won’t have the process I described. It is not only our intelligence that allows us to use all the sound gathered by our ears to understand. First our hardware along with the software in our brain filters the sound and gives them meaning. Only then we use the filtered sound for listening. If we didn’t have strong tools for filtering meaningful noise in a way that can be effectively used in communication, we would have hard time with it as well.

Anonymous 0 Comments

>why can’t great apes speak?

Technically, humans are great apes.

Anonymous 0 Comments

Some point in the last 5 million years after we forked away from the last common ancestor shared, in newfound isolation both groups started developing genetic differences that were beneficial to them.. Every new born gets 60 genetic mutations where each one can big or small, good or bad..

Pretty much every racial characteristic we have come from mutations that we embrace collectively

At some point a child was born with the FOXP2 gene, a new genetic mutation.. It granted a very subtle difference that allowed the kid to not just grunt out emotional outbursts, but to use vocalizations as constant identifiers for recognizable objects and such which was much more energy efficient than belting out emotional outbursts as sole means of communication. Some accepted it, some didn’t.. There were other forks but the subset of homo genus that embraced speech among many other energy efficient changes likely aided them in proliferating into today’s modern day human

To this very day people are (Very rarely) born with mutations where the FOXP2 gene disappears just as mysteriously as any genetic trait appears.. They have great difficulty using speech even though there is no detectable physical difference

Anonymous 0 Comments

Their brains have all the hardware for vision and none for speech. So you know that universal human reaction to be afraid of snakes and see them in any patterns of leaves etc? Well that takes a big portion of our brain and all the room in a monkey brain. They’re really good at understanding what they see and incredible eye hand coordination, like that chimp finishing the american ninja course without a bother.

I know this because most of the inovation in computer vision and AI research can be traced back from the findings on rhesus monkeys in the 80s seeing how neuron layers activate and are creating the thought/notion of a fruit. And I was quite surprised how big of a chunk of brain is used for that and how the same form and structure is present in the human brain, how in monkeys that’s the dominant hardware they have, and how in us we have so many other structures like the cortex.

Anonymous 0 Comments

Long story short it appears that they don’t have the ability to ask questions.

Asking questions gives rise to a conversation and the ability to build a language.

At this point only humans and one parent have ever asked a question.

There are multiple other examples why they would happen in ability to have what would be considered conversations.

On the side note dolphins have full conversations with each other and actually make extended plans and create games between themselves.

So this probably isn’t a completely accurate answer but it almost certainly has something to do with it.

Anonymous 0 Comments

The sign language is overstated. You can teach them to make signal for a product. But have you ever seen anybody have conversation with any ape via sign language?