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5 Human/Chimpanzee Differences

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Want to know exactly what makes you special? Ok, read on.

Charles Darwin was primarily interested in divergence. He wanted to know what evolutionary pressures made organisms different. In The Descent of Man he spent a considerable amount of time contemplating what it was that made humans unique or special. Comparisons with the “mental faculties” of apes was often used to explore this:

We must also admit that there is a much wider interval in mental power between one of the lowest fishes, as a lamprey or lancelet, and one of the higher apes, than between an ape and man; yet this immense interval is filled up by numberless gradations.

This quote reveals two things:

1) Darwin was aware that human intelligence made us completely distinct from the rest of the animal kingdom, even from our closest relatives.

2) Darwin was also aware that this intelligence must have evolved gradually over time from a species that was “more ape-like” (i.e., more like a chimpanzee) than like a modern day human.

However, Darwin did not (and could not) have a grasp on what those exact differences between humans and the great apes were. The behavioural research just wasn’t well developed. In fact, modern day primatologists are still searching. We are getting closer every year. But what do we know right now? Can we make a list of the key intellectual differences between our closest relatives and humans? Some primatologists think we are not there yet.

In the first animated video I made for The Advanced Apes YouTube channel I focused on some of the cultural and technological similarities between humans and chimpanzees. Understanding the similarities between chimps and humans has been the focus of many primatologists, including Dr. Jane Goodall.

The work by Goodall and her primatological successors have definitely closed the separation between humans and the rest of life. I have emphasized these similarities in the past:

[Chimpanzees] make tools, use language, understand symbols and build shelters. They also develop long-term bonds, live in highly social groups, make jokes, manipulate, deceive, empathize, and show care for other members of their group and other species. The behavioural differences have been relegated to artificial human-constructed continuums of complexity.

But of course it doesn’t take an advanced science degree to know that humans and chimpanzees are different. As Neil deGrasse Tyson stated, we can build a telescope that can see the beginning of space and time. Chimpanzees cannot. Tyson’s meditation on this topic is correct, but slightly misguided (he is not an evolutionary theorist after all). The difference between humans being able to construct a powerful telescope and chimpanzees only being able to make very simple tools is an example of a proximate difference. It does not tell us anything about why humans can build telescopes and chimpanzees cannot.

I am a theorist that takes after Darwin. I care about divergence. I care more about what separates us from chimpanzees than what we have in common. Of course I find the similarities intriguing. The similarities make the quest for understanding the differences that much more difficult and interesting. At the moment we do not have a complete list of the differences. But I also feel like there has been enough research to make a list of a few differences that we can be relatively certain exist.

Here is my list (no particular order of importance):

1. Control of Fire

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Chimpanzees don’t control fire. I have written about this in the past. From extensive paleoanthropological research we know that control of fire was an important development in our own evolution. The ability appears to have emerged with Homo erectus ~1.5 million years ago. This implies that an enlarged neocortex is responsible for making the higher-level connection that:

A) Fire is something that can be safely contained

B) Fire is something that can simultaneously improve an individual’s diet and provide safety from predators

The development of fire use in our past was transformative. It allowed us to cook meat, considerably widening our diet, consequently providing the fuel for rapid encephalization. It also (likely) allowed us to make the permanent transition to a terrestrial niche.

For chimpanzees today, their lack of ability to control fire probably prevents them from doing these two key things that allowed our ancestors to take over the biosphere.

2. Culture Packets

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Human culture comes in very broad packets. If you grow up in Japan (for example) you will learn a set of connected things (i.e., eat a certain way, speak a certain language, become exposed to certain artistic and sport traditions). These cultural behaviours are statistically correlated in packets. The reason this occurs in our species is because we are advanced social learners that both want to conform to norms and enforce conformity of norms in many situations.

This cultural phenomenon does not manifest itself in chimpanzee groups. Chimpanzee cultural behaviours do not really appear together in packets. Chimpanzee culture appears to be largely dependent on ecological stimulation. Each chimpanzee group exhibits multiple complex cultural behaviours, but those behaviours are not statistically correlated with each other. Chimpanzees in Senegal may make spears and chimpanzees in Tai may more frequently construct rock hammers, but those behaviours are not packeted together with more complex aggregations of behaviours. So it is really misleading to say “Senegal chimpanzee culture” or “Tai chimpanzee culture”. But for humans it is quite accurate to say “Japanese culture” or “English culture”, even though that packeted cultural variation is more fluid than the boxed categories make it seem (i.e., someone from Japan can enjoy eating characteristically English food and listening to characteristically English music, and vice versa).

From an evolutionary perspective this behaviour is definitely driven by the desire to conform for non-functional reasons (i.e., wanting to wear a certain item of clothing to fit in with the larger group or sub-group). But it is also driven by society demanding a certain level of conformity (i.e., no shirt, no shoes, no service). I can’t just walk into a class or store with no clothes on. Everyone would freak out. This type of behaviour does not exist in chimpanzee groups. There is no normative sanctions for lack of conformity. Higher-level group conformity just doesn’t matter to chimpanzees. Higher-level group conformity matters enormously to humans.

3. Complex Language

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Language obviously sets humans apart from the rest of the animal kingdom. Other animals can communicate. Some animals can communicate with a high degree of complexity. But humans have by far the highest linguistic capability. Like fire and like social conformity, this is likely a higher level process produced by the neocortex.

Our neocortex allows us to think in complex hierarchies. Chimpanzees also have a neocortex. But their neocortex does not allow for the level of hierarchical complexity that ours does. So let’s see where chimpanzee hierarchical complexity ends and ours diverges giving us complex language capability and access to more information than any other species that has ever existed.

Level 1 of linguistic hierarchy: “|”

This is a straight line. We all know that this is a straight line. But it can also be more than a straight line. If we add more straight lines “|||” humans can realize that this may be a symbol abstractly representing three units of something. Perhaps it represents three pieces of fruit or three sticks. Chimpanzees also understand this. Chimpanzees can do basic math. So can many other animals.

Level 2 of linguistic hierarchy: “A”

Now we have put the three lines together into a higher level symbol. These three lines represent a letter. Humans can obviously understand this level of hierarchy. We know that “A” is not just three lines. And that in order for three lines to represent an “A” they have to be ordered in a specific way. Three lines organized like “|||” do not represent an “A”. Chimpanzees, can also understand this. This level of information is clear to them.

Level 3 of linguistic hierarchy: “APPLE”

Now we have taken a bunch of (mostly) lines and connected them all into different symbols: “A” “P” “P” “L” “E”. We have established that chimpanzees have matched our ability so far. They can understand that each of these letters represents a meaningful symbol. This is information that their neocortex has the ability to process. And… they can also understand that when these five letters are together in a particular order, that they represent something abstract: a specific piece of fruit. The word “APPLE” can be successfully associated with an object in nature. They understand that the order matters. “APPLE” means specific fruit; “ALEPP” does not, even though the same symbols are being used.

Level 4 of linguistic hierarchy: “Nim wants apple”

In level four we have another hierarchical jump. Humans can string words together to form an even more complex idea. We have moved from knowing that “APPLE” means a specific type of fruit. Now with this higher order we can communicate that someone specifically wants a specific type of fruit. This is essentially using language to communicate a base level desire. Chimpanzees can also do this. They can string words together to communicate a base desire inside their own brain.

Level 5 of linguistic hierarchy: “Do you like apples?”

On this level something special happens. I do not just want to communicate a base level desire. I want to know something about the universe. I want to know if another entity likes something. I want to literally get inside the mind of another being. This may not seem too profound because humans do this so naturally. How could it possibly be revolutionary for humans to ask a question? See what I did there?!

The desire for humans to ask questions is remarkable. And it is even more remarkable to know that after decades of linguistic training, no chimpanzee has ever asked a question. No other animal on the planet has ever asked a question. Only humans do this. Who asked the first question?

This is a significant linguistic gap. From here we speed away from chimpanzees. Our neocortex allows us to inquire into minds of other beings. We can learn more and more about the universe. We can make higher and higher level connections between information:

Oh, Jenny likes apples. But I don’t really like apples. Why does she like apples and I don’t like apples? Does it taste differently to her than it does for me? Is her experience of the apple different? If so, why?

And so on. The more complex we get from here the more chimpanzees have no clue what is going on. This is essentially why physicist David Deutsch has asserted that it is fundamentally possible for humans to understand all of reality, but it is fundamentally impossible for chimpanzees (or any other species). The world actually is stranger than they can ever understand.

You can now thank your neocortex.

4. Teaching

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This difference is truly critical. Humans want to teach others (look at what I do with all of my precious time!). We want others to understand. What is crazy is that we want others to understand even if they are not direct kin or even part of the same group. Now I may invest more time and energy into teaching some people over others, or I may only want to teach certain people if I am getting financially compensated. But we also do it altruistically. The human brain likes sharing information. And we have evolved for being taught as well. This works in a similar way to conformity. We want to conform (to varying degrees) but we also expect others to conform (to varying degrees). Teaching works in the same way. We have the ability to teach (and we do depending on circumstance), and we also have the ability to be taught (again, depending on circumstance).

In contrast, chimpanzees do not actively teach each other and they appear to be poor students as well. Teaching is fundamental for human success because it allows us to increase cultural complexity. It allows us to continue cultural traditions for thousands of years. There are words that we speak today that came into existence tens of thousands of years ago. This is because of our fantastic ability to teach and be taught.

How this ability evolved is really still unknown. It is really hard to know exactly what genes enabled this ability. And obviously “teaching” and “being taught” do not fossilize. However, we can infer from the degree of cultural complexity that certain behaviours would be too complex to exist without some level of advanced cultural transmission (i.e., purposeful teaching with language). Therefore, it is likely that teaching has always been fundamental for modern humans and probably existed in some rudimentary way in species like Homo neanderthalensis, Homo erectus, etc.

5. Technological Evolution

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Finally, my personal favourite difference: technological evolution. Other animals make technology (i.e., a physical object other than the animal’s own body or appendages as a means to extend the physical influence realized by the animal). But no other species systematically increases the complexity of technology. And no known animal can make a technology that would require multiple generations of knowledge to create. For example, an iPod or the Hubble Space Telescope are remarkably complex technologies that could never have been constructed by the earliest modern humans. They did not have enough cultural information to make such devices. So it is not our DNA that enables the Hubble Space Telescope. It is our ability to increase the complexity of technology from generation to generation by passing down useful cultural information.

Chimpanzees do not engage in a process of technological evolution. Now, of all the five differences this one may not remain on the list. It could be that chimpanzees do engage with a primitive process of technological evolution and that we have not detected it because the process is so primitive and slow. In fact, if we could have observed australopithcines for a couple generations we may have come to the conclusion that they were not engaging in technological evolution. However, by studying the paleoanthropological record we now know that they were engaging in a very slow technological evolutionary process. Either way, as far as we know chimpanzees do not even do this, but we need more research to be sure. And even if they do, it pales in comparison to the technological evolutionary process that exists in the human species by several orders of magnitude.

Final Thoughts

You are a human. And because you are a human you had the intellectual capacity to understand this blog post. That makes you special. No other animal can acquire so much information and transmit it so well to other conscious entities that share their neocortical complexity. Darwin knew there was something special about us. We are now getting closer to realizing what that is. Now the question becomes, what will we do with this intelligence? How will you use it to change the world?

Discuss this on Hubski or let me know what you think on Twitter!

 
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