Are We More Chimpanzee, or Bonobo? The Evolutionary Roots of Aggression in Humans

avatar
(Edited)

Bonobo Group Hug
Bonobo group hug Magnus Manske lagged on user 2.0.png
Image credit: Magnus Manske (Source), Laggedonuser (Author). Used under CC 2.0 license. The picture illustrates an observed behavioral pattern in bonobos: they'd rather get along, than fight.

There was a time when it was believed chimpanzees were more closely related to humans (in evolutionary and genetic terms) than any other animal. In recent years though, chimps have had to share this special status. It turns out that bonobos share as much genetic material with humans as chimps. As a matter of fact, some studies indicate that bonobos may actually be closer to humans than chimps.

Besides regarding this information as a bit of entertaining trivia (and also suggesting a moral obligation to treat these non-human cousins humanely), why do we care about these primate relatives? Does this information have relevance to our understanding of human behavior? As it turns out, probably.

Chimpanzees at Chester Zoo, UK
Chimpanzees_at_Chester_Zoo Photograph by Mike Peel www.mikepeel.net cc by SA 4.0.png
Image credit:Photograph by Mike Peel (www.mikepeel.net) (author). CC-BY-SA-4.0. Please attribute as per the author line.

Bonobos and chimps share about 98.7% of human DNA. The two species share about 99.6% of DNA with each other. It is believed that humans, chimps and bonobos descended from a common ancestor. According to an article published in Nature, "more than 3% of the human genome is more closely related to either bonobos or chimpanzees than these are to each" other.

About 4 to 7 million years ago, humans split off from their chimp cousins and began a distinct evolutionary development. Bonobos, it is believed, split off from chimps about 1 million years ago and began to evolve independently.

The Youtube video link below shows the fossil skull of what is believed to be the chimp/bonobo/human common ancestor, Nyanzapithecus Alesi. This 13-million-year-old infant's skull was found in Kenya.

Image credit: Produced by
DeAnza Design & Manufacturing Technologies Dept.)

Again, this begs the question, Why should we care? Is this just another bit of trivia? No. What's interesting about this information is that when the two ape species split, they evolved distinct patterns of aggression. The chimps became hunters, fighters, killers. They not only hunt other animals, but they kill each other. They practice infanticide. Though bonobos have been known to hunt, they do not kill each other. They do not practice infanticide.

An Adult Male Chimp Snatches an Antelope From a Baboon
an adult chimpanzee snatches a deat antelope from a baboon Ikiwaner 1.2.png
Image credit: Ikiwaner. Used under CC 1.2 license.

Do these patterns of aggression in our cousins tell us anything about ourselves?

That would be hard for me to say, but fortunately, I don't have to. In 2018, a wonderfully relevant (to this discussion) article was published in PNAS that looked at aggression in bonobos, chimpanzees, and humans (other animals are also referenced). The article suggests that scientists can trace the evolutionary trajectory of aggression in these three species by comparing the types of aggression that appear in each today.

Proactive and Reactive Aggression
It has been suggested by many researchers, including those who wrote the above-referenced article, that aggression may be characterized in two ways: reactive and proactive. In order to understand the difference between these types of aggression, we can look at one human emotion: jealousy. This can result in both reactive and proactive aggression.

The Methodist Taylor (Sic) Caught in Adultery
The Methodist taylor caught_in_adultery  The Trustees of the British Museum, released as CC BY-NC-SA 4.0.png
Image credit: © The Trustees of the British Museum, released as CC BY-NC-SA 4.0. 1778 etching.

If a spouse walks in on a partner engaged in an adulterous act, there will likely be a surge of neurochemical responses that may prompt an aggressive impulse. That seems to be the case in the etching featured above (The Methodist Taylor (Sic) Caught in Adultery) This is reactive aggression. The surge of chemicals and cascade of impulses defines reactive aggression.

Bullying
Bullying_Verbal Edith Castro Roldán, Oscar Manuel Luna Nieto 4.0.JPG
Image credit:Edith Castro Roldán, Oscar Manuel Luna Nieto. CC 4.0. Bullying is characterized as proactive aggression, as are stalking, ambushing and premeditated homicide.

In some cases, after the immediate jealous response there is a cooler anger that sets in. There is a desire for revenge, the desire to hurt the people who have engaged in the adulterous act. This form of aggression is cold, calculated and has a clear purpose. This is, by definition, proactive aggression. It is not characterized by the cascade of chemicals seen in the initial response to the adulterous act.

Types of Aggression in Humans and Anthropoid Cousins
According to the PNAS article referenced previously, humans and chimps demonstrate high rates of death in intergroup aggression. In simple terms, chimps will form coalitions in order to stage attacks on other chimp groups. The goal is to gain some advantage, maybe territory, maybe food. This is called conspecific aggression. According to the PNAS article, "Humans are the only other primate species (besides chimps) in which similarly high (or higher) rates of death have been recorded in intergroup aggression".

La Cambe German Military Cemetery, Calvados, Normandy, France
Perspective_La_Cambe_cemetery_Calvados_edit  Jebulon cco1.png
Image credit: Jebulon. Used under CC CC0 1.0 Universal Public Domain Dedication. Waging war is an expression of conspecific, proactive aggression.

While humans and chimps demonstrate high levels of proactive aggression, (the following quote from PNAS) "...in bonobos (P. paniscus) no proactive aggression leading to intergroup killings has been observed,... and no other evidence of proactive aggression toward conspecifics has been reported."

By contrast, both bonobos and chimps demonstrate higher levels of reactive aggression than humans do. A number of studies come to this conclusion by comparing the rate of spontaneous skirmishes among humans in small-group settings, with spontaneous conflicts in groups of bonobos and chimps.

Comparing Expressions of Reactive and Proactive Aggression
aggression chart2.png
Image credit for the chart: agmoore. Public domain. Images within the chart (all public domain) credited at the end of the blog.

Are We More Chimp, or Bonobo?
The Max Plank institute looked at the genome of bonobos, humans, and chimps. The Institute found that "a small bit of our DNA, about 1.6%, is shared with only the bonobo, but not chimpanzees. And we share about the same amount of our DNA with only chimps, but not bonobos". One of the pieces missing from the chimp genome, but shared by humans and bonobos may be a small part of the aggression puzzle. There is a protein present in bonobo and human urine which "allows the individual to detect differences in scent to pick up social cues." This may be a piece in the puzzle that explains why humans and bonobos have lower rates of reactive aggression than chimps. Group members in these species can read each other's cues and thus may be able to decrease incidents of reactive aggression (spontaneous conflict).

I've linked to a rather entertaining and informative National Geographic Youtube video on bonobo sharing and empathy:


Conclusion
I began this essay by asking whether humans are more bonobo than chimp. I haven't really answered that question on an individual or group level. There are obvious genetic connections between humans and their primate cousins. Among humans there are certainly individual differences that are both genetic and epigenetic in nature. There is, for example something called, the 'warrior' gene. And, there is a recognized correlation between testosterone levels and aggression. But as a guide to figuring out how and why each of us is aggressive (or not aggressive), that is a puzzle that has yet to be sorted.

accent  black and red.jpg

Resources Used in Writing This Blog

Image credits for the chart on aggression (all public domain):
Bonobo Face
Evanmaclean
Chimp Face
Frontierofficial
Human Face (Victoria Kamāmalu, Prime Minister of Hawaii, circa 1860)
James J. Williams

Selected Research Sources
1.https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4287885/
2.https://leakeyfoundation.org/new-13-million-year-old-infant-3.skull-sheds-light-on-ape-ancestry/
4.https://www.animalcognition.org/2016/07/31/bonobos-make-love-and-war/
5.https://www.psychologytoday.com/us/blog/out-the-darkness/202002/making-love-instead-war
6.https://www.science.org/content/article/bonobos-join-chimps-closest-human-relatives
7.https://pasa.org/awareness/bonobos-and-chimpanzees-which-ape-is-which/
8.https://leakeyfoundation.org/new-13-million-year-old-infant-skull-sheds-light-on-ape-ancestry/
9.https://www.animalcognition.org/2016/07/31/bonobos-make-love-and-war/
10.https://www.psychologytoday.com/us/blog/out-the-darkness/202002/making-love-instead-war
11.https://www.science.org/content/article/bonobos-join-chimps-closest-human-relatives
12.https://pasa.org/awareness/bonobos-and-chimpanzees-which-ape-is-which/
13.https://www.pnas.org/content/115/2/245
14.https://www.dvm360.com/view/bonobos-or-chimpanzees-which-are-our-closer-relatives
15.https://link.springer.com/article/10.1007/s11948-020-00219-z
16.https://www.science.org/content/article/bonobos-join-chimps-closest-human-relatives
17.https://www.nature.com/articles/nature11128
18.https://www.deanza.edu/dmt/contact.html
19.https://www.reuters.com/article/us-science-infanticide/infanticide-common-among-adult-males-in-many-mammal-species-idUSKCN0IX2BA20141113
20.https://www.newscientist.com/article/dn14926-loving-bonobos-have-a-carnivorous-dark-side/
21.https://d1wqtxts1xzle7.cloudfront.net/38595818/IJFP-2332-287X-03-302-with-cover-page-v2.pdf?Expires=1642888460&Signature=LIOX8BWbFXplyKd78AbdITCUAa6uQcKKGnPBDPlXwJnUATVbzf4isEAIf4pHKu6-D9RIkIQJIfxV78UDyzI7BxWqbe5uQ43A~xAVqUr4Nb9gf6MSzFH0ddShYr9ItEJEgbzNu9g~RPZchh5vIaNhQSUCBgXvtLEssH8qdKMykT0iOeyZOHGz8Q11V~52pRgVJljt7vvApe24Vrt7r~0U12CSc3SgcmY~vsZwMGJJqY5q8cxZoBKN0ykcbInyy0WCQz2Q~FNXUiyTNUyZFw30Fj7zKoobebPPakwJZbac2WPSj8eedrJgg6grVLNCerjPYZ5d4HjjEA5CpSZ5G3DCgA__&Key-Pair-Id=APKAJLOHF5GGSLRBV4ZA
22.https://bigthink.com/the-past/war-and-peace/
23.https://brill.com/view/journals/beh/aop/article-10.1163-1568539X-bja10111/article-10.1163-1568539X-bja10111.xml?language=en
24.https://psycnet.apa.org/record/2010-23649-006
25.https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5789961/
26.https://www.cdc.gov/genomics/disease/epigenetics.htm
27.https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3693622/
28.https://www.theguardian.com/science/2015/may/14/early-men-women-equal-scientists
29.http://thescienceexplorer.com/nature/bonobos-form-all-female-coalitions-target-violent-males

Thank you for reading my blog

Hive on!

stemsocial logo.jpg

lmac graphic3.png

Inkwell logo.jpg



0
0
0.000
27 comments
avatar

You described about the chimpanzees very well, i know things now that didn't know before. Thanks for sharing this thing with us.

0
0
0.000
avatar

Thank you, @rikoy, I really appreciate that. I'm grateful you read this long blog.

I write blogs now, but I used to be a teacher. So, when someone says they learned something, the teacher in me is very happy.

Hope you are having a great day.

0
0
0.000
avatar

Very fascinating! It is mind blowing that we're so closely related to the bonobo, the hippies of non-human primates. But it shouldn't be surprising, I suppose. Like humans, chimps can be aggressive and even go to war in similar ways to humans. On the other hand, humans are also very social and we love being in groups like the bonobos. Also like the bonobo, we can be tender, gentle, and playful. Bonobos seem to spend a large amount of their time in intimate social interactions in pairs and groups. Their conflic resolution technique is to make love not war, hence the hippie reference. So perhaps it shouldn't be surprising that we share so much genetic material with this particular primate group.

Thank you for this well researched and delightful article @agmoore!

0
0
0.000
avatar

Hello @litguru,
Thank you for reading and for your most interesting feedback.

I didn't bring up the sexual aspect of bonobo bonding because that seems to be the thing that fascinates people almost more than anything else. I just thought I would skip over it. But yes, I like your analogy. They release tension through sexual contact. There are no boundaries. It's like a handshake. And the hippie reference works beautifully. As you know, the 60s was my generation. I went through NYU 65 -70. (It took six months longer than it was supposed to.) We had a casual attitude towards just about everything back then. Make love, not war. Perfect. Return an insult with a smile, or at least try to.

I think the whole discussion (about aggression and its evolutionary origins) is fascinating and I almost always have a hidden agenda when I write these article about animals. We really have to treat them better. This discussion might give one or two people pause who think animal experimentation is fine.

Hope you are well. Thanks again for the visit and comment.

Regards, AG

0
0
0.000
avatar

What a beautiful article. I would challenge the logic (not the evidence). When it comes to the phenotypic result, what matters more?: locus of mutation or the total difference? Very close genotypes can show massive differences in phenotype. Just saying.

Second. The aggressions do not need to be related at all, so what looks like a synapomorphy is maybe non. I have a highly speculative hypothesis: humans have a stomach pH that is in the scavenger spectrum, there are herbivores with very high acidity but we also know that humans have a preference for stinky food. Food that your cat would and could not touch. Surströmming (rotten Swedish fish as an extreme example). Do scavengers like Wolverines or Hyenas have higher aggression than carnivores? I would say so. Aggression is centered around the property which originally is the cadaver.

Now, something strikes me: when a chimp or gorilla approaches a female of a silverbacks harem, then it is not because of the female, it is because of the position (that means mating-privilege). When humans show aggression because their mate is approached by another male OR female, it can put shame on the one thats wife/husband has been taken, sure BUT the one that e.g. wants to have the girl like the young Paris wanted Helena, is really there because of the girl/women not because of the position of the other male or because of a mating privilege. Paris was a coward. And this "mate = property"-thinking is not only mythology nor is it restricted to men, but there are also lots of cases where women do horrible things because another woman took her "property".

0
0
0.000
avatar

Hello @lauch3d,
A pleasure to see you here and get your feedback. That is exactly the response I was hoping for.

When I start one of these blogs, it's with a question (several questions). I read something somewhere and want to learn more. Then I do the reading and check out sources that lead to sources. In the end I present a case. And then I hope people will do what you did--challenge it, present alternatives. Give me something more to think about.

The aggressions do not need to be related at all

I agree. They aren't necessarilly related, but in thinking about this hypothesis, I learn about something about bonobos, chimpanzees and humans. Maybe I learn to think more analytically about aggression.

I'm fascinated by your PH hypothesis. It took me a minute to find this article: The gut microbiome correlates with conspecific aggression in a small population of rescued dogs (Canis familiaris) (!)

I thought of Troy while I was writing this, but I had to reacquaint myself with the characters, etc. so I just skipped over it.

Thanks for this most interesting comment, which will lead me now to do more reading. That I like. Hope you are peaceful and well.

Regards
AG

0
0
0.000
avatar

I like your assumption. It brings another interesting alternative to the topic, that is actually quite a complicated one (as anything that involves genes, behaviours, etc.). The problem I see with correlations... is that they are correlations (yeah I know...). However, it is a good step in a direction that is interesting to follow.

Cheers!

0
0
0.000
avatar

Very informative and well-written article. Thanks!

0
0
0.000
avatar

I love it when you stop by, @one-eye. I very much appreciate your kind words. Hope you are having a great evening.

0
0
0.000
avatar
(Edited)

Always look forward to your articles. This one was great. You have such a wide range of subjects. Thank you for your contributions to the community.

0
0
0.000
avatar

Hello @pokerm,
You are always such a good supporter. That is much appreciated. When I write I try to meet the standard you and my other readers expect of me.

Hope you are having a great weekend.

0
0
0.000
avatar
(Edited)

Thank you for this very informative and important article. It certainly was an interesting read.
I'm not sure what the answer to that question might be. But there surely isn't much of differences between humans and those other species. And I'd definitely advocate treating all creatures respectfully.

I'd like to draw attention to the "learned aggressive behavior" aspect of this subject. Dr.Robert Sapolsky have done and published some work about a group of baboons and how events led to a complete change of the population's behavior and tendencies for aggression.

Here's a short Youtube vid that I quickly found, if you're interested in hearing that story (not the best, but the others are in longer vids/lectures)

He has many other interesting lectures and stuff related to chimps, bonobos, baboons,and humans.

0
0
0.000
avatar

Hello @yaziris, Thank you for visiting my blog! We share an interest in science, you and I. We are two people who love to write, and to learn.

And I'd definitely advocate treating all creatures respectfully

Thank you! I go a bit further. It troubles me that the suffering of animals is tolerated so easily. I think if we understand how related all of us (animals and humans) are, we might find certain activities morally reprehensible.

I didn't get a chance to check out Dr. Sapolsky, but I am eager to hear what he has to say. Mondays are busy for me, this Monday especially as I fell behind on my obligations last week.

I really appreciate your visit, your attention to my blog, and your feedback. See you over at the Ink Well later :)

0
0
0.000
avatar
(Edited)

That is a wonderful piece of text. I had heard a lot about the connection with chimps (as most of us did, probably) but never considered the existence of a so close connection with bonobos. Really fascinating!

The coolest part is that you ask an interesting question to which there is no unique answer. What our genome tells us is not everything. During the course of my reading of your blog, I wanted to refer to epigenetics as a definite additional ingredient to build an answer to the question. You however were faster than me (in your conclusions ;) ).

Thanks a lot for sharing this with us!

0
0
0.000
avatar

Thank you @lemouth for reading my blog and for your feedback. I'm glad you found the material interesting. It was a nice adventure, collecting material and writing this. I love the animals and found the discussion about aggression fascinating. As @lauch3d suggests (comment above) this discussion is just beginning. We don't know so much.

In a way, the close relationship of our primate cousins to us is tragic. Their bodies are useful in research. We feed off them like parasites as we do research to learn about ourselves. That has to be troubling to any thinking person.

One of the nice things about writing this blog is I get to sort through wonderful pictures. Picking the most interesting for readers is a challenge.

Thank you again for reading and commenting. It's really heartening that you take the time. Today is Monday... your blog will have another treat for me as my understanding of the universe grows. See you over there later.

0
0
0.000
avatar

You pointed exactly why I would not ever be able to do research in anything close to biology. I would not be able to experiment on living species. Note that I neither say that we should not do it, nor that we should do it. It is ... yeah complicated. I am happy with fundamental physics in which ethical questions are never in order.

Next Monday, I will write a special blog for our special event. Nothing really new for those following me for a long time, but maybe something interesting to grasp to new readers.

It is now time to read @lauch3d's comment :)

0
0
0.000
avatar

I respect your reservations about working in biology. My granddaughter wants to work (help) with animals, but has decided against being a veterinarian because this involves experimenting on animals. She is instead hoping to pursue a path that leads to occupational therapy, and in this capacity she will learn about animal anatomy and be able to help them.

I appreciate that you don't feel comfortable taking a stand on this issue. As you know, I am comfortable in my opposition to animal experimentation. That is a long discussion I may take on one day here (in STEMsocial), using of course only data and verifiable information to support my position :))

0
0
0.000
avatar

Feel free to engage with such a discussion. I am very curious about the reactions that it could trigger... Some become very 'aggressive' (here is a new connection to the present blog), emotional and very passionate on these topics. This will result in interesting debates / discussions, I am sure of it!

0
0
0.000
avatar

Interesting piece.

It is just a bit of a mystery how as similar as the genome of humans/chimps/bonobo are, chimps and bonobos are not prime candidates for organs donation for xenotransplantation - but pigs (in the light of the most recent successful transplantation of a pig's heart into a human). Could it be that there is something I'm missing?

0
0
0.000
avatar

Hello @gentleshaid, Thank you for reading and commenting. As for your suggestion, I came across two articles that address the issue you raise. The first deals with ethical concerns, and the second deals with the fact that organ transplant is actually more likely with a primate (for reasons detailed in the article). As always, you have an interesting perspective.
Hope your son is doing well.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6356609/
https://www.nature.com/articles/s41598-020-66311-3

0
0
0.000
avatar

That 'taylor' has some balls, to cheat on a woman 3 times his size!

It does seem overall, to me, that chimps are more similar to us in terms of aggression (proactive, I guess). Spartans killing infants that weren't considered healthy is one example that came to mind when I read that chimps "practice infanticide".

0
0
0.000
avatar

That 'taylor' has some balls, to cheat on a woman 3 times his size!
😅

The only thing that saves us is the tiny bit of bonobo in our genome :))

Thanks for stopping by, @alexanderalexis.

0
0
0.000
avatar
(Edited)

That was nice read :3

With comparing DNA is wonder if a weighted approach is more insightful as certain parts of are more meaningful than others when comparing one species to the other.

0
0
0.000
avatar

Hello @mathowl,
Thank you for reading and for visiting my blog. What you suggest sounds reasonable, but I defer here to my profound ignorance of genetics. I don't know. I think in a way it is convenient to blame genetics for (human) aggression. That allows us to look beyond the role of epigenetics (social factors), which we can control. Even if we look at something like Huntington's Disease, which is genetically programmed to go off like a bomb in an individual, we see that lifestyle actually influences onset.

I appreciate the feedback :)

0
0
0.000