If you watch chimpanzees from different parts of Africa, you’ll see them doing very different things. Some use sticks to extract honey from beehives, while others prefer leaves. Some use sticks as hunting spears and others use them to fish for ants. Some drum on branches to get attention and others rip leaves between their teeth.
These behaviours have been described as cultural traditions; they’re the chimp equivalent of the musical styles, fashion trends and social rules of humans. They stem from the readiness of great apes to ape one another and pick up behaviours from their peers. But a new study complicates our understanding of chimp cultures. Kevin Langergraber at the Max Planck Institute for Evolutionary Anthropology has found that much of this variation in behaviour could have a genetic influence.
Langergraber studied almost 250 chimps, who came from 9 groups, including 3 from the west African subspecies and 6 from the east African one. For each one, he noted whether they performed any of 39 different behaviours, and he sequenced DNA from their mitochondria (small energy factories in animal cells that have their own small accessory genome).
Langergraber found that the differences in their genes were mirrored by differences in their behaviour. Groups of chimps with starkly differing cultures are also genetically distant and the greater the gap between their behaviours, the greater the gap between their genes. And only a small number of actions varied between groups that were genetically similar.
Frans de Waal, a renowned chimp researcher from Emory University, praises Langergraber’s work. “[It] is not dismissive of the culture concept, but adds a complication to the picture,” he says. “The data now indicate that chimpanzees, which are genetically incredibly diverse, have an overlap between genetic and cultural diversity that will need to be addressed. It is wonderful data, and makes the culture story all the more fascinating.”
These new results don’t mean that chimp cultures are all “in their genes”. After all, many of the behaviours that have fallen under the banner of chimp culture are complex traits that are unlikely to be genetically determined. “No one would assume a gene for ant-fishing in the chimpanzee in the same way that no one would assume that some humans have a knife & fork gene and others a chopstick gene,” says de Waal. “However,” adds Langergraber, “it is possible that groups differ in the frequency of [genetic variants] that lead (however indirectly) to differences in the propensity and predispositions for individuals to fish for ants.” They might be more dextrous, for example, or like the flavour of ants.
Nor does Langergraber’s work downplay the role of culture in explaining the varied behaviours of chimps. For a start, both he and de Waal note that you’d get the same results if you looked at humans, and no one would think less of our culture as a result. De Waal also says, “The finding is consistent with culture spreading from group to group by female migration, which may be based on learning but still would produce a correlation with genetics.”
Many previous studies have shown that apes (and probably even monkeys) can imitate and learn from each other. As a result, traditions and habits can spread in non-genetic ways. This is the essence of culture, and it means that individuals and groups end up behaving in varied ways. But the key message from Langergraber’s work is that it’s not clear how much of this variation in the wild is a result of cultural traditions.
If anything, the main message from the study is that the methods primate researchers use need to be improved. Consider one of the landmark studies in this field: a paper from 1999, in which Andrew Whiten and Jane Goodall documented 39 chimp behaviours that were common in at least one group but absent in others. The duo reasoned that this variation wasn’t down to differences in the chimps’ environment – for example, some fished for termites and others didn’t, even though both groups had access to these insects.
This line of reasoning is called the “method of exclusion” and it’s commonly used in the field. Researchers infer the existence of cultural traditions by ruling out other explanations. The trouble with the approach is that while scientists typically exclude ecological explanations (like the presence of termites), genetic ones tend to slip under the radar.
An alternative might be to look at how differently individuals behave within the same group, depending on how closely related they are. Are close relatives more likely to act in the same way, or are such parallels more common among chimps who interact with each other more frequently? Langergraber also says that you can often tell how a behaviour was transmitted by looking at how it spreads through a group. If they’re imitating one another, the behaviour gets picked up very quickly in a short space of time, as the number of potential tutors suddenly skyrockets. These accelerating patterns are a sign of social learning at work.
Reference: Proc Roy Soc B http://dx.doi.org/10.1098/rspb.2010.1112
Image by Delphine Bruyere
More on chimp cultures:
- Pocket Science – back-scratching disabled chimps and free-falling aphids
- Chimps prefer to copy others with prestige
- Culture shapes the tools that chimps use to get honey
- Cultured chimps pass on new traditions between groups
- The chimpanzee Stone Age
If the citation link isn’t working, read why here
August 18th, 2010 at 10:02 am
I was initially skeptical of this as another example of genetic determinism gone awry, but you clarified the paper quite well. I thought the sentence:
“However,” adds Langergraber, “it is possible that groups differ in the frequency of [genetic variants] that lead (however indirectly) to differences in the propensity and predispositions for individuals to fish for ants.”
really offered the most salient insight. Initially it sounded like he was dismissing “culture” by substituting some genetic / ecological determinism but the description makes it clear that he’s arguing that what we define as cultural variation is simply an inherent capacity among primates that might be influenced by positive responses to various stimuli. An interesting extension of this thinking might be to question which came first, the natural propensity or the behavior that supports that propensity.
Thanks for the summary. Interesting stuff.
August 18th, 2010 at 10:13 am
I think Langergraber did a fantastic job with the paper. He makes it very clear in the discussion that he’s not dismissing the cultural idea. His point is really very nuanced so I’m glad it comes across in the piece.
August 18th, 2010 at 11:00 am
While it is possible that genetics have driven ‘cultural’ trends, it is the less likely of possible scenarios. It is more likely that valued group activities, such as termite fishing or nut cracking, have provided pressures that pushed natural selection in particular genetic directions. One would expect to find greater genetic diversity and greater cultural diversity between groups that are geographically more distant. This is because culture, like genes, is passed from generation to generation. Groups that are geographically closer have greater contact and more opportunity to exchange both cultural knowledge and genetic material, making culture and genetics covariable with geography. This article represents genetic determinism in its weaker form (propensity), but it is still deterministic.
August 18th, 2010 at 1:22 pm
The first thing I thought was, “correlation doesn’t imply causation.” Which is addressed, to some extent.
It would be nice if we could experiment on this by dropping an infant from an ant-fishing group into a honey-fishing group (always assuming we could get the honey-fishing group to accept the “orphan”), and then watching how the orphan grows up. Does he/she attempt to ant-fish? Or does he/she learn how to honey-fish?
August 18th, 2010 at 5:45 pm
Genetic proximity, physical proximity, and cultural influence must all be very strongly correlated. I don’t see how they could tease out a genetic component without transporting populations. Without such teasing out, this all seems very speculative. Maybe east Asian fingers really are better suited to chopsticks than to forks, but the genetic variation doesn’t suffice to demonstrate it.
As erudite and nuanced as the paper is, does it actually tell us anything?
August 20th, 2010 at 7:50 pm
Thinking aubout this by days in the meantime. Yes, this paper tells me a lot, especially the way Ed explaning it. But why? I still couldn’t say exactly.
Nevertheless I can tell you about a guy here in the neighbourhood. With a very east-Asiatic face [and probably genes, because both parents origin from China]. Only hearing him talk, you would swear to hear an aboriginal for his local tongue. So it’s a funny surprise seeing his face after that, throwing your expectations pretty through eachother. I don’t know if he has a chopstickgene. I only know he’s eating with knife and fork in the same way as he speaks: like any other local native overhere.
I don’t believe the nature OR nurture. Too many kids I’ve seen with different behaviour. Not only immediately after birth, but even in the womb. Even 2 kids in the same womb from the same parents, behaving differently. Or cats or whatever animal you would like to look at. What I see, is so to say: interaction between nature and nurture from the earliest beginnings. Non of both predisposing all, but instead developing the one in interaction with the other.
What I like the most in this post, is the confirmation of the role of genes [nature] WITHOUT denying the role of culture / learning / interaction [nurture]. For me, especially about such close relatives to me as the great apes, sure this is telling me something!
Nathan, though perhaps not scientific, is this in some way a usefull answer to you?
August 20th, 2010 at 8:05 pm
Thinking aubout this by days in the meantime. Yes, this paper tells me a lot, especially the way Ed explaning it. But why? I still couldn’t say exactly.
Nevertheless I can tell you about a guy here in the neighbourhood. With a very east-Asiatic face [and probably genes, because both parents origin from China]. Only hearing him talk, you would swear to hear an aboriginal for his local tongue. So it’s a funny surprise seeing his face after that, throwing your expectations pretty through eachother. I don’t know if he has a chopstickgene. I only know he’s eating with knife and fork in the same way as he speaks: like any other local native overhere.
I don’t believe the nature OR nurture. Too many kids I’ve seen with different behaviour. Not only immediately after birth, but even in the womb. Even 2 kids in the same womb from the same parents, behaving differently. Or cats or whatever animal you would like to look at. What I see, is so to say: interaction between nature and nurture from the earliest beginnings. Non of both predisposing all, but instead developing the one in interaction with the other.
What I like most in this post, is the confirmation of the role of genes [nature] WITHOUT denying the role of culture / learning / interaction [nurture]. For me, especially about such close relatives to me as the great apes, sure this is telling me something!
Nathan, though perhaps not scientific, is this in some way a usefull answer to you?
August 21st, 2010 at 11:59 pm
Hmm…just to play devil’s advocate here on the notion of relationships between genes and culture…the DNA they sequenced was mitochondrial DNA, which is passed on from mothers to children. If chimps with more distant mtDNA sequences have more variation between their cultural behaviors, this could merely serve as evidence that cultural transmission in chimps is mostly or entirely carried out through mothers.
Now, I would not at all be surprised to find out that there was a genetic component to cultural variation in chimps, but considering the evidence they used, it’s hard to draw definitive conclusions.