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Time and again humans have domesticated wild animals, producing tame individuals with softer appearances and more docile temperaments, such as dogs and guinea pigs. But a new study suggests that one of our primate cousins—the African ape known as the bonobo—did something similar without human involvement. It domesticated itself.
Anthropologist Brian Hare of Duke University's Institute for Brain Sciences noticed that the bonobo looks like a domestic version of its closest living relative, the chimpanzee. The bonobo is less aggressive than the chimp, with a smaller skull and shorter canine teeth. And it spends more time playing and having sex. These traits are very similar to those that separate domestic animals from their wild ancestors. They are all part of a constellation of characteristics known as the domestication syndrome.
The similarities between bonobos and domesticated species dawned on Hare during a large departmental dinner, where he listened to Harvard University anthropologist Richard Wrangham hold forth on bonobos. "He was talking about how bonobos are an evolutionary puzzle," Hare recalls. "'They have all these weird traits relative to chimps and we have no idea how to explain them,'" Wrangham had noted. "I said, 'Oh that's like the silver foxes!' Richard turned around and said, 'What silver foxes?'"
The foxes that Hare mentioned were the legacy of Russian geneticist Dmitri Belyaev. In the 1950s Belyaev started raising wild silver foxes in captivity and breeding those that were least aggressive toward their human handlers. Within just 20 generations, he had created the fox equivalent of our domestic pooches. Instead of snarling when humans approached, they wagged their tails. At the same time, their ears became floppier, tails curlier and skulls smaller.
Belyaev's experiments showed that if you select for nicer animals, the other parts of the domestication syndrome follow suit. Hare thinks that a similar process happened in bonobos, albeit without human intervention.
Rape, murder and warring neighbors are all regular aspects of chimp life. Bonobo societies, however, are far more peaceful. Hare thinks that the chimplike ancestors of bonobos found themselves in an environment where aggressive individuals fared poorly. By selecting for the most cooperative ones, evolution forged a "self-domesticated" ape, just as Belyaev produced domestic foxes by picking the most docile ones.
Hare has now laid out his ideas in a new paper, written with Wrangham and Harvard colleague Victoria Wobber, and published online January 20 in Animal Behaviour.
Bonobos and chimpanzees diverged from a common ancestor between one million and two million years ago, after the formation of the Congo River separated one population of apes into two. Considering that neither species can swim, the two populations "might as well have been on different planets," Hare says.
Both groups faced very different environments. Hare thinks that the northern population, which would eventually become chimps, had more competition from gorillas for their food. They were forced to compete fiercely with one another for whatever was left. Females got a particularly short shrift, and were easily overpowered by males for both sex and resources.
"In bonobo-land in the south, the story was different," Hare explains. "The river would have protected the ancestors of bonobos from gorillas." With more food to go around, females could gather in larger groups, form tight social bonds, and better resist the advances of males. In this land of plenty, the least aggressive males, who opted for alliances rather than brute force, were most likely to mate. South of the river, the nicer apes thrived.
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27 Comments
Add CommentAwesome. My guess is that Hare and Wrangham are probably onto something here. de Waal's idea of the Pan common ancestor possibly being more bonobo-like than chimp-like shouldn't be discounted. However, because chimps are numerically superior and more geographically widespread, it seems more likely that bonobo traits would be more idiosyncratic and derived rather than the other way around. Again, that's just a guess.
Reply | Report Abuse | Link to thisThis idea of bonobos being immature chips is not new at all. Matt Ridley's outstanding books on the evolution of human nature (and nurture) from the 1990's and early 2000's discuss bonobos and are carefully referenced. The real interesting question is have humans become domesticated as a result of civilization and urbanization?
Reply | Report Abuse | Link to thisHomo Sapiens as an ultra-domesticated ape was also my first thought, although I would guess civilization would be a consequence rather than a cause. Our skulls are bigger than our ancestors, though, so I guess it's not the whole story...
Reply | Report Abuse | Link to thisEven if the Bonobo/Chimp split came from a Bonobo-like ancestor that wouldn't discount the theory. They could have already self-domesitcated- but later-competative pressures could have forced domestication out of the Chimp.
Reply | Report Abuse | Link to thisRegarding human domestics; certainly it would be needed before an advanced civilization- I would go for domestification before civilization rather than the other way around.
A more domestic tribe would more likely band together than a non-domestic tribe and be able to create a civilization.
Evolutionary pressure would favour a co-operative domestic tribe. Human skulls expanding is probably more a relation to our brains growing rather than becoming less-domestic.
Actually human brains have decreased in size about 10% in the last 30,000 yrs, but body size has decreased too so it could be meaningless.
Reply | Report Abuse | Link to this@sijodk:
Reply | Report Abuse | Link to thisWhilst skull size might have gone up, if the gloom and doom merchants are correct about the increasing sexualisation of society, perhaps it should really be looked upon as being a positive sign indicating a tendency towards more domesticated human beings.
All your comments, who is trying to sound smart, is making this too complex. This autumn, I acquired a house guest...a mouse. I first heard it chewing on something, and I concluded that it was wood it was chewing on because it was hungry. I then saw the mouse sneak over to my dog's food bowl and sneak some food out and run like crazy to the buffet. I didn't hear the wood chewing anymore when the mouse discovered the dog food. I am a big time nature lover and I found the mouse quite entertaining and thought that I would make this mouse my guinea pig. The next time I saw the mouse, about thirty minutes later, I cornered it in a corner and told it, "If I see you getting into my babies food before he is finished or hear you chewing on any wood, I will kick your ass up one side of this wall and the other... do you understand me?" The mouse was scared to death and I could've killed it if I wanted and I think it knew that. It is now January and I haven't heard the mouse chew on any wood, but, I do see it go to my dogs food bowl, after he is finished, and get a couple of bits and return to the buffet. Can a mouse understand us and domestic itself to us...I think this mouse did and I somewhat enjoy having it around. I haven't seen another mouse in the area since I gave it permission to stay with me and my dog. Don't make life complicated and think that we humans are the smartest thins on this planet, because we are not.
Reply | Report Abuse | Link to thisI dread to think what would happen to the bonobos if chimpanzees became established across the river.
Reply | Report Abuse | Link to thisIt is most unfortunate that humans do not make some attempt to domesticate themselves. Rape, murder and warring neighbours are all very distinctive traits of homo sapien behaviour !
Reply | Report Abuse | Link to thisinteresting assocation between food and aggressiveness ...
Reply | Report Abuse | Link to thisI recall something about sharing - meat tends to raise hackles e.g. lions, dogs snarling at each other over a kill, while fruit (as more prolific, scattered and so less valuable per unit) was more likely to be shared with equanimity.
So - where food is scarce, high value food like meat is difficult to obtain, which requires aggressiveness/testosterone to acquire, etc.
Where food is plentiful - no need to raise the hackles - we can all sit around and chat over a nice cup of tea ...
Given that phylogenetically the common chimp's social behaviour (male dominated aggressive hierarchies) is the "default" ape, and indeed primate, social structure, and that sexual dimorphism is much greater in most ape species than bonobos, including us, it is more likely the bonobos are the divergent species than the chimps.
Reply | Report Abuse | Link to thisHow do you explin tasmanian devils?
Reply | Report Abuse | Link to thisSkull size is mostly a matter of bone surface needed to attach jaw muscles to.
Reply | Report Abuse | Link to thisHumans learned to cook so their heads got smaller (but brain-cases didn't.) Dogs were given food, so they didn't need to hunt & eat raw meat, perhaps bonobos had more food and don't partake in raids like chimpanzees.
But that doesn't explain the second line of silver foxes - The silver foxes that Belyaev kept as his control by not selecting them for breeding because of their friendly qualities. They live a (safe) life in a cage with food provided, so why wouldn't the undomesticated foxes look like the domesticated ones?
What is my doctor doing there
Reply | Report Abuse | Link to thisNever heard about ancient Homo Sapiens Sapiens having a larger brain size than modern humans. Homo Sapiens Neanderthalensis did, however, have a larger brain (10%, give or take a few), than modern Homo Sapiens Sapiens, and they were stockier, sturdier and stronger too. H. Heidelbergensis, a probably last common ancestor of HSN and HSS, had a brain capacity comparable to or slightly lower than modern humans. Difficult to draw conclusions here...
Reply | Report Abuse | Link to this@beanfeast: I'd call that short term fluctuations in the level of sexualisation of society. Ancient Greek pottery often depicts drinking men with erect phalli - not something most contemporary upper middle class people would put on display in their living rooms. What's interesting in this context is how much sex individuals of the genus Homo had half a million years ago, but the data is probably tricky to obtain.
But humans are domesticating themselves (without really thinking about it) When we lock up rapists, murderers, users of violence and all the other traits that we disapprove of, we are removing them from the breeding pool for a period of time and making it likely that when they do return to society, that they are less likely to be in a position to attract a mate (a criminal record makes it much harder to get a decent job which leads to a lower standard of life which in turn reduces their ability to attract a mate)
Reply | Report Abuse | Link to thisEvery time we send our troops to fight our wars, some of them don't come home, thus over time, the stay at home none fighting types will come to be a larger percentage of the population.
Our current society puts a premium on co-operating and constructive working with others and reduces the ability of those who prefer violence to breed - Humans are becoming more bonobo than chimp!
When food is plentiful- population grows until food is no longer plentiful.
Reply | Report Abuse | Link to thisWhat causes Bonobo populations to not get to the point where food is all consumed and allows them to live their happy utopian lives so that they can continue to domesticate themselves?
Thanks for this piece, Ed. I'm glad Hare et al are careful to contextualize this as a hypothesis, since as they say we don't have fossils to indicate whether the last common ancestor of chimps/bonobos was more chimp- or bonobo-like. Certainly a very interesting idea.
Reply | Report Abuse | Link to thisInteresting idea. Something similar could have been a stage in human evolution which could help explain one of our most unusual aspects,hidden oestrus and the absence of the rut. the only other mammal with the former does however rut. Normally a weaker rut means less sex so how can it be selected for? Only social sexuality like among Bonobos would allow it, but not favour it. I'd suggest the rut was lost to make bipedalism easier. In other great apes the female genitalia swell as one of the signals of oestrus, but that would incapacitate female bipeds making them vulnerable to predators and raise problems for foraging, as well as being a pain in the ass.
Reply | Report Abuse | Link to thisIf the hormone that stimulate swelling also control the release of pheromones, the loss of the rut would be an advantage. If regular sexual contact occured anyway in the context of social interaction then sociability would become a major factor in reproductive success. This selection would lead to more and more complex social relations and that would require more intelligence in both sexes. The evolution of language has had many practical advantages, but in it's early stages they woukd have been very limited. If its function were only to facilitate social interaction, that would be eough to favour the trait. The later practical benefits are side effects. Chatting about frivolities still has a major role in getting another into bed.
Our brains have been oversized starting a couple of million years ago, costing enormous investment in biological and energy costs. For most of that time we still hunted and gathered much like chimps. You don't need such a big brain for practical reasons. I think of it more like a peacock's tail, except that for interaction to work both sexes need similar inteligence.
Despite what we see on the news, humans are usually very peaceful, cooperative and altruistic. Cooperation is more important than competition, otherwise we could not have evolved the whites of the eyes or a 15-18 year chilhood.
Mirror neurons are built-in empathy, and we"ve got much more of them than any other species studied. Altruism is not limited to relatives and is much more common than violence. Mutal aid is basic to our survival strategy.
Conflict between groups is also part of our evolution The last 3M years are marked by a highly unstable climate so wild variations in food resources. Sometimes you fight to survive, thinking of "us" before "them" We have mechanisms for that too, but I don't have space left to deal with that. Recent research seems to me to support my hypotheses.
This discussion reflects the possibility that the very notion of domestication is complex. It has various degrees and variations, and is particularly prone to observer bias and context (I would guess that Victorians considered a somewhat different mix of traits than we in the 21st century; and likewise different contemporary cultures would make differences among observers). I noted how the thread quickly leapt from domistication among bonobos to among humans. Could the geographic hypothesis (a river runs through them leading to two different cultures) explain differences among human groupings? Did the interaction of humans with quasi-self-domesticating species (dog, to a limited degree, cat, maybe even rat) and with more traditionally domesticated species (cow, horse, camel, chicken) itself play a role in human domestication?
Reply | Report Abuse | Link to thisI also was struck by comments (particularly in the chicken-egg bonabo-chimp origin debate) suggesting that domestication as an evolutionary process is not a one-way street. Does the process seen in the feralization of species (wild horses in US, e.g.) occur in humans?
Does epigenetics, which allows a species to make rapid functional changes in response to environmental changes - without fundamental genetic changes - play a significant role in the process described as domestication?
This article puts a new light on the lifelong, immature pre-adolescent, immature mentalities that one can see in large segments of our "privileged multi-generational white-collar suburbanite" population.
Reply | Report Abuse | Link to thisNice as these people are.. and as much as I like them individually... in so, so, many cases it is like being with kids who know how to act adult.... like we see in the occasional pre-teen or early teen.. an ability to act adult on the surface for a while, while still retaining all of the inner motives and incompleteness of the ungrownup being that they are.
We see this, for example, in the "occupiers" nationwide. Participate or observe their discussions online at Facebook, or on person ... and one gets the feeling one is with a batch of middle schoolers who are equally unsophisticated and also unaware of that lack, as are pre- and adolescents.
In my view, it is not so much that they are wholly genetically doomed to being forever-children but it seems one must experience some intensity of life, some maturing experience in order to be tempered by life into a fully mature adult.
This seems to be experience(s) that must occur in a window from say age 16 to age 26 or so.
The standard lifepath of the sheltered, privileged, pipelined-through-life child of multi-generational white-collar suburbia seems to leave them with precious years in which to have those tempering experiences.
They are nice as "all get out".. .and well meaning... but some vast portion of this segment of the population simply seems to never, ever finish growing up.
At the least.. they seem to have had the maturing process so retarded that it takes them all of their life to finish growing up (if ever) and they only, finally attain adulthood when they are ready for assisted living and have lost a spouse or two to nasty diseases.
This is not true of the healthy adult who is not sheltered and who faces any of dozens of kinds of tempering life experiences... experiences that are not momentary but that are of year(s)duration.
Those who have been in the military, for example, and were not parade-ground or homeside-office-worker military.. but who were on some "pointy end of the stick" kind of job.... who faced their own mortality with no lifeguard but themselves and their immediate companions... most often have been tempered by life and become adults.
We see no end of these large-children gaffing up our society as they infest politics and other social organizations.
Bonobos appear to be much more civilized than a lot of people I know !
Reply | Report Abuse | Link to thisI don´t see the conection between domestication and civilization. As a rule "civilized people" (from people who live in cities)are much more violent and exhibit more criminal and antisocial behaviour than "non civilized" tribes.
Reply | Report Abuse | Link to thisI think this whole hypothesis is quite hare-brained.
Reply | Report Abuse | Link to thisFIRSTLY, the Congo River is not a hermetic seal between its two banks. Though chimpanzees may not swim, I would suspect that downed trees in the thick rain-forest should facilitate river crossings.
SECONDLY, there are chimpanzees living on the bonobos side of the Congo River. These chimps live further up the east bank, in Tanzania and thereabouts.
With no gorillas or other competitors for food and so much time to make sex, did the bonobos multiply out of control or did they also invent family planning?
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Reply | Report Abuse | Link to thisDomestication is defined as any training that uses a system of punishments and rewards. We've all grown up in an auto-domesticating culture.
They had controls by selecting aggressive foxes too. They had at least one line of aggressive foxes and one line of tame-selected foxes. Later it was found that the tame foxes were physiologically different. The melatonin system was altered. http://www.springerlink.com/content/u80w6240506tnj48/
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