In a startling and thought provoking article recently published in the journal Human Evolution, Roffman and colleagues propose that chimpanzees (Pan troglodytes) and their “cousins”, bonobos (Pan paniscus), need to be reclassified to the genus of Homo, the same genus as human beings (Homo sapiens).
That’s a BIG step!
In this article, we’ll explore why Roffman and many other biologists and anthropologists think that chimps and humans are so closely related that they belong in the same genus and we’ll explore some of the advantages and disadvantages that would result from the reclassification.
First, let’s look at where they are classified now and see how that was decided.
Chimpanzees were first observed and recorded by western civilization in 1738 and classified as Simia troglodytes in 1770 by a German Naturalist, Johann Friedrich Blumenbach. In 1816, Lorenz Oken, another German naturalist, coined the genus name Pan after the Greek god of nature and wilderness and ever since they have been designated Pan troglodytes (troglodytes from the Greek trogle “hole, mouse-hole” and dyein “go in, dive in”). In 1933 it was determined that the bonobo was different enough to be given its own species name, paniscus, a diminutive form of Pan.
The researchers above mainly compared physical characteristics and a few fossils to arrive at this tree shown below.
It was taken from this article and summarizes that evolutionary thought. As you can see, it has the great apes, Homininae, splitting into 3 different lines, Gorillas, Chimpanzees (Pan) and Humans (Homo). What Roffman and others are proposing is that we eliminate Pan as a separate genus and include them in the Homo genus.
Two of the most important ways modern evolutionary classifiers look at and define relatedness are through fossil evidence that we can use to compare physical characteristics, and genetic evidence.
Let’s look further into what these two lines of inquiry have told us.
Fossils: What does the fossil evidence tell us?
Because chimpanzees and apes live in tropical forests with acidic soils, their remains are rapidly degraded and seldom forms fossils. The chimpanzee fossils that have been found are a few teeth between 545 and 284 thousand years old. It usually takes millions of years to form a species, so that’s not enough time to provide solid evidence.
Ok, fossils didn’t tell us very much about chimp-human similarity.
Genetics: What does the genetic evidence tell us?
How genetically different or alike are Homo and Pan?
One way to investigate this is to compare versions of the same protein to see how similar they are.
Because many of an organism’s genes contain instructions that tell cells how to make certain proteins, if two organisms are closely related, and they make the same proteins with only small differences, then we can say they are closely related. If their proteins differ in major ways, then they are less closely related
Almost 50 years ago Allen Wilson and Vincent Sarich performed a molecular analysis of several proteins that were common to both apes and humans. They concluded that apes were closer to humans than had been previously suggested by paleontologists who had based their decision on the scant fossil evidence.
These protein studies had humans and apes diverging from a common ancestor around 4–6 million years ago but could be as early as 8 million years ago. Isn’t 8 earlier?
But that was half a century ago! Isn’t there more recent data to rely on?
in 1990 Morris Goodman and colleagues looked at the DNA sequences around the β-globin gene in primates and basically found that they confirmed the evolutionary tree shown above. They also suggested that the divergences we see happened about 8 million years ago.
But there’s a problem with DNA studies like theirs. One factor that confounds side-by-side DNA sequence comparisons is how fast genes change over time. This rate of change in the genome is commonly referred to as the molecular clock. And certain regions of the genome are known to change faster than others. These are called mutation hot spots.
Other studies in the late 1990s showed that the molecular clock was ticking slower than originally thought. A study in 2016 by Moorjani pushed the date for divergence back to 12.2 million years ago! And some scientists still argue about how accurate this tree really is.
Can’t we just sequence and compare their complete genomes to give us the evidence we’re looking for? Modern sequencing technology has, in fact, made that possible and it has been done.
In 2005 Varki and Altheide sequenced the entire chimpanzee genome and made the first whole human-chimpanzee genome comparisons. What they found was that the two complete genomes differed by only about 4%!
That’s remarkable but further research that looked only at the genes that both species shared showed a 1.2% difference in the molecular differences. Wow, that’s really alike! Here’s a quote from this article:
“No matter how the calculation is done, the big point still holds: humans, chimpanzees, and bonobos are more closely related to one another than either is to gorillas or any other primate.” (bolded type not in original)
As you can imagine, there are lots of ongoing studies like this one that looks at molecular hot spots, to try to figure out what all this means.
Are there other ways to explore Homo-Pan relationships besides fossils and genetics? How about looking at how they act?
Consciousness and Behaviours: What stories do they tell us?
If two creatures with similar physical features show similar behaviours, that might be a strong indication that they are closely related to each other.
There are many people that have looked at both of these qualities over the years. One of the most famous is Jane Goodall and the stories of her living and interacting with the gorillas and chimpanzees in Gombe Park, Tanzania, in Africa are well documented.
She catalogued 5 major discoveries about how chimps and humans act in similar ways.
- In 1960 she saw a chimpanzee alter a stick to make a tool to “fish” termites out of their nest and then eat them.
- Also in 1960 she discovered that chimpanzees are omnivores. They eat meat. Their diet includes bush pigs, colubus monkeys and other small mammals.
- Chimpanzees start and wage wars! She was the first person to document one tribe engaging in war against other tribes to kill other chimpanzees.
- She documented that they have strong mother/infant bonds and siblings share strong familial bonds, just like humans.
- They exhibit compassion. She observed chimpanzees mourning the death of other chimpanzees and “orphans” were adopted by other members in the community.
Here’s some additional qualities of both chimpanzees and bonobos that they share with humans:
- Bonobos can communicate using a keyboard device.
- Chimps and gorillas can communicate using American Sign Language.
- Bonobos are capable of utilizing wood, antler and stone tools at the level of early Oldowan technology, and their long-bone marrow extraction techniques are on par with those of early Homo spp.
- They make markings that persist over time that are similar to cave-art icons and recollect their meaning over time. Thus, they remember the past and can testify to that in the future.
- trail marking, mapping and exploring their environment is a significant component of their daily life (Savage-Rumbaugh et al., 2007)
- They exhibit musical abilities and have musical preferences.
- They can paint and draw.
This quite an impressive list! But there is still more….
The foundation of human relations is how we communicate with and act towards one another.
How do Pan species communicate?
Chimps and bonobos all demonstrate they have the basic components previously thought unique to human language. They utter meaningful sounds, exhibit use of syntax/vocal learning and control and can recognize both individuals and groups based on certain ways in which they vocalize. Sue Savage-Rumbaugh has spent many years documenting this aspect of Pan behaviour.
One of the more common calls of both male and female chimpanzees are the pant-hoots. They have been studied for many years and are known to serve many functions including aiding the formation of social groups, indicating group or individual hierarchy and territorial dominance between groups, indicating the location of individuals in a traveling party and indicating the presence of fruit trees or other abundant food resources.
The calls are highly variable and individuals can be recognized by their call.
Pant-hoots are also used in courtship. The more dominant a male, the louder and longer his call to indicate his greater fitness and thereby impress and secure a potential mate. Have a listen to some here and here.
Most telling of all, often in areas where they have been hunted by humans they stop the calls to remain hidden and undetected. This is important because the calls are loud and travel great distances and often serve to reveal their location to other members of their social group.
Now that you’ve read about some of the many wonderful, intelligent and human-like qualities and things Pan has and can do, we need to head back to our original question — Are Chimpanzees Really Humans?
What happens if the answer is yes?
Basically, we would have to treat them in the same way we treat other humans. Here’s a few of the disadvantages and benefits to both humans and chimpanzees resulting from that decision.
Some Disadvantages of Reclassification to Homo:
Currently chimpanzees are captured, bred, raised and used as model organisms that are representative of humans in biomedical research. You can’t use people in biomedical research without their informed consent. Therefore, this would have to stop.
In many African cultures, they are hunted, sold and consumed as food. You can’t hunt and eat people so this would have to stop and will affect local economies by eliminating jobs and income. It might also create a black market for those people that still want to eat meat from chimpanzees and bonobos. So the killing would still continue but would now constitute an unethical and criminal act.
Chimpanzee body parts are still being sold on the black market. This would have to stop. Higher levels of enforcement will be needed to completely eliminate this.
The idea that you can “own” a chimpanzee would no longer be something you can do. Since that would constitute a form of slavery, no chimps or bonobos could be kept as pets.
Chimpanzees are popular creatures and people go to zoos to view them. They are bought, sold and traded by zoos to live in unnatural crowded conditions for public display. This would have to stop and might reduce zoo attendance and income. At the very least, zoos would have to rethink and redesign if and how they might establish and maintain a colony in such a way that chimps would have a fair degree of privacy and a more natural environment, in effect, create a sanctuary.
All of these and similar exploitation of Pan species would become illegal criminal acts, punishable by the justice systems of the world. In fact, there is an ongoing court case to establish the habeus corpus rights of chimpanzees in the American legal system.
That’s a big step! And it affects a LOT of people. Many of them will object. It goes against their traditions. It affects their economy. It eliminates sources of food and income.
So it is not a step we should take lightly.
Some Advantages of Reclassification to Homo:
Pan embodies our early Homo/hominin cultural heritage. There is much we can learn from them about our own evolutionary past if we continue to study them in ethical ways.
Chimpanzees are an endangered species. Reclassification would give a huge boost to efforts to halt their extinction. In the early 1900s, there were more than a million chimpanzees. Today estimates place their numbers between 150 and 250 hundred thousand left, and the numbers continue to decline. Leaving things as they are is not an option if we truly wish to save them and turn this around.
Chimpanzees and bonobos have a long history of interaction with local indigenous people with mutual benefits to both cultures.
In 2015 Dr Roffman interviewed tribal elders from Mali. The elders remember times of peaceful coexistence with Pan. They recounted stories of the harmonious life between wild chimpanzees and villagers. This was before foreign hunters and others such as missionaries infiltrated and caused suspicion and fear to appear amongst both groups.
Pan had a sacred place in tribal heritage. Elders told about how their forefathers learned various medicinal plant applications in the distant past by observing chimpanzees using them.
We have only scratched the surface and revealed the tip of the iceberg in terms of of chimpanzee cultural diversity. There are about 10,000 Pan communities left in Africa and most of them have not been studied. We have a lot to learn to begin to understand how these different communities are structured and behave.
This includes things like studying their survival strategies — How else do they make tools? How do they construct their shelters? How do they choose a location to inhabit? What plants do they use for medicinal purposes? When do they become nomadic? And on and on.
Not only will such knowledge open a window to the understanding of our own ancient past. It also harbours the potential to directly benefit present day humanity by providing new sources for medicines to treat various ailments.
Ethical Considerations and Recommendations:
Regardless of whether or not you think Pan should be reclassified to Homo, the evidence does point to the notion that they are fully conscious beings with activities and cultures very similar to humans.
Many of the researchers who have spent serious time with these primates have come away with the feeling that they are more like us in morphology, behaviour and genetics than we have given them credit for in the past.
They communicate with each other. They recognize each other and their own social group. They make tools to gather food. They live in a variety of extreme habitats including deserts and cliffs and construct shelters to do so. They wage wars with other chimpanzees. They care for orphans. They enjoy certain forms of music. They can paint and make art. They find and treat themselves with specific medicinal plants.
They exhibit what is known as indexicality. This is a fancy term which means that when they see a feather, they know it means there are birds in the area. When they see a paw print, they know there are lions around and act accordingly. Thus, they make associations from past experiences and think abstractly.
If you search on the internet, I’m sure you can find even more facts like those I have already mentioned. Here’s a classic book about the subject.
Whether or not we reclassify them to the genus Homo, we need to respect them and give them secure, natural places to live. This can be done by designating reservations and sanctuaries for them. A gradual transfer of all Pan from captivity to reservations and sanctuaries must take place, since these hominin sister-species to humans should not be imprisoned and exhibited against their will.
We need to stop selling them as property to own and eliminate all markets that do so. We need to continue to establish their legal rights.
We need to release them from all laboratories, zoos, and entertainment ownership contracts.
I could go on and on but then this would start to be a book, not an article. And I’m not the person to write this book. Others are way more qualified than me.
Finally, we get back to our original question; Should chimpanzees — Pan — be reclassified as Homo?
What I would love is to see respectful comments from all sides to hear what other people think.
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Until we talk again,
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