Mims on Chimps: I agree and disagree
Published by Greg February 25th, 2007 in Science Essays, EvolutionIn a recent blog on Scientific American, Christopher Mims claims “...We Shouldn’t Be Surprised That Chimps Hunt With Spears.”
and provides these reasons (briefly stated here … see the blog for the details):
1. They use objects in their environment as tools.
2. [they] modify objects….
…[ other reasons that are not so relevant]
So…
Chimps are capable of inventing tools that are suited to the resources that are available to them (in other words, suited to both the kinds of materials they have available for tool manufacture and the kinds of foods they might want to obtain with those tools). Chimps are also capable of transmitting knowledge about tool use and manufacture from one individual to another.
Thus, spears are just one more example …
This argument on the face of it is logical, and to some extent I agree with it. However, there are reasons why this use of tools by chimps is potentially very important (and new).
First let me quickly say that I am not one of those Paleoanthropologists who goes all gaga over meat and hunting. My view is a bit more informed and sophisticated than that, if I may say so myself. (see “Man the Hunter” and “An Evolutionary View…” for more discussion).
But there are important qualitative differences between the various “tool use” categories we see in chimps.
For example, there is a set of behaviors using objects that involve communication between individuals. This has been likened to symbolic behavior. There is another set of behaviors linked to “extraction of embedded objects” (like termites). This is a categorically distinct subtype of “foraging” with objects.
If we only knew about the foraging/embedded object behavior then discovered another example of that, a “so what” response might be appropriate. But if we only knew about that foraging/embedded object behavior then discovered an example of “symbolic communication,” then it’s “go gaga over the chimps” time.
Th question with this newly documented behavior is whether or not this represents a new category. It is my own internal uncertainty about this that makes me go back and forth over “well, this is cool, but…” and “Holy crap, Gomer, can you believe what those chimps are doing?”
These chimps may be poking at stick into a hole to get out some food. Bush babies, termites … whatever. Or they may be “hunting with spears.” That is qualitatively new and different.
But it is also possible, likely in fact, that it is neither. What they actually appear to be doing (and one may have to actually read the article instead of the press reports to get this) is the following: The chimps appear to be stunning/killing the bush babies in order to make it safer and more effective to reach into a hole-o-bush baby and thus extract the furry tidbit without getting bitten. And we should remember that getting bitten by a bush baby may be worse than getting bitten by a lot of other critters. This is just a guess on my part, but one primate biting another (even though prosimians and apes are pretty distantly related) may be worse than average in the zoonotic disease department.
So I personally do NOT feel that this is chimps exhibiting spearing behavior. I would count spearing as a different kind of behavior. But it MIGHT be a categorically novel behavior with respect to what we already knew about chimps.
It is also worth noting that this behavior was observed 22 times, and only once did it actually work. THIS may be the really important finding of this research. What does this tell us? It could indicate that this behavior was just “invented” and the chimps are experimenting. Perhaps they will improve the method or just get good at it, and we will see more success in the future. Perhaps they will give up on it. Perhaps it will continue to be an ineffective behavior but it is so much fun that they will keep doing it. Like fishing in humans. (But now, wait, it is mainly female chimps doing this … persistence in the face of continuous failure, just for the fun of it, is more of a guy thing. Like fishing in humans.)
But what is the chance that these primatologists just happen to observe a behavior in the process of being discovered and tried out? Zero or close to zero you say? No, actually, it’s not that low. There are currently a few dozen distinct behaviors known among chimps across all the study sites, At least one behavior has been observed to change function while a study was in progress (the “meaning” of one of the symbolic behaviors at Tai). So, the chance of seeing novelty … in the from of a shift in behavior .. is about one in a bunch (statistically speaking). That’s pretty high considering the number of study sites and the number of chimps under continuous observation. (Other behaviors have seemingly fallen out of use, and still others observed only after a longish period of observation of a particular group. But it is hard to quantify sampling and observer effects in those cases.)
I think the researchers should be actively working on the hypothesis that this is a novel invention.
8 Responses to “Mims on Chimps: I agree and disagree”
- 1 Pingback on Feb 28th, 2010 at 11:10 pm
Greg, I noticed that some news reports had those female chimps also “chewing the end of the spears” i.e. to sharpen them. I would look close at that report, and ask “isn’t that the symbolic part?” b/c we impute that those chimps are actually honing the points to kill, rather than as you state, stun the bush babies, which is a symbolic leap of inference on our part…
I’m not saying they are not sticking the bushbabies, just that sticking bushbabies in a hole is not “using a spear” except only in the most technical sense.
The chimps modify the end of the stick, seemingly to make it sharper, sometimes. They also do this for termiting (but I quickly add … not necessarily these chimps. It’s the Gombe chimps who “termite.” I’m not sure how else these chimps use sticks in this manner at all.
Hi - Jill Pruetz here - I am somewhat pressed for time, but I thought I could clarify a few points (no pun intended) about the discussion in progress. The modification of the end of the hunting stick is very different from the modification of grass blades, slender twigs and vines for termite fishing. This behavior is also exhibited at Fgonoli. If you read the scientific article closely, you will see that we use terminology such as, “in the manner of a spear” etc. Multiple definitions of spear fit the behavior in question, and using “spear” as a verb rather than as a noun may give you a better idea of what is going on. The popular press has run with this of course., and Spear(!) is used very liberally… In fact, we discussed a number of other terms, such as “dagger”, and I see that “blidgeon” has been recommended and even “ramrod”. The latter two suggestions do not apply to the behavior very well, and I fear that “dagger” would get the same treatment as spear from the popular press… In terms of success rate, the rate is not so low as for solitary male monkey hunters at Tai, and the behavior doesn’t appear to be so costly as monkey hunting, so it is not surprising that it is fixed in the population. We are examining the behavior in detail, as you would imagine so hoefully would be able to say if more age-sex classes adopt it, in which case you could argue it is a new innovation. We were aware that chimps here ate bushbabies for years, but relied only on indirect data (bushbaby remains in feces!) so were not aware of how they acquired them unti lthe chimps were (recently) habituated to our presence. I’d love to continue, but I should in fact be writing a lecture! Sorry if there are typos, etc. - I am not able to view the entire window in which I am writing…
The issue is a little oversimplified in many popular science publications like the scientific american, but I agree ith you in a general sort of way. One of the really interesting items in more thorough research on this topic is hether or not chimps can learn about the general from the specific, i.e. extrapolate knowledge gained in a specific incident and apply it in similar contexts, and to what degree they can engage in inventive tool use. A good example of this is research on the Japanese Macaque, in hich it appears that they learned to wash sandy food in the sea and then taught this behavior to future generations. Anyay, interesting post I’m glad I stopped by.
Jill: Thanks so much for adding your comments!!!
You have a choice. You can call it a “dentally modified limbic terminus” or a “dagger.” The latter will create obnoxious confusion in the press, but at least it will generate press, and the chimps need the press!
I just want to add (for now) some additional thoughts. When thinking about chimp technology and material culture in relation to human technology and material culture (and the evolution of both, but people tend to focus on the latter) it is common to think of this as two stages in a progression form “non human” to “human.”
The nature of chimp material culture is inherently incredibly important and since chimps and humans are both African hominoids, it bears tremendous importance in understanding human evolution, and of course behavioral evolution in general … not to mention chimp evolution.
But it may be misleading to think of a spectrum or a time line with chimps on one end and humans on the other, where our job would be to generate hypotheses about the various intermediate steps … novelties of capacities, etc. … added one or a couple at a time … in between. Yes, we do want to hypothesize about the steps in behavioral evolution and material culture in human prehistory … it is the line or spectrum that is the problem.
I would not be surprised if there were capacities that are required for a “chimp like” ancestor to adopt the practices of the genus Homo present in chimps but in a sense unconnected to other existing behaviors. The difference, in other words, is not necessarily the absence of some capacity to mentally work something out, but rather, the social (or other) inability to implement this, or more importantly, social (or other) forces making something that chimps otherwise “could” do simply impossible. This is the essence of the social contract idea (as in the Wrangham et al paper, and my suggestions about handaxes, etc). The social contract allows division of labor and delayed consumption of food. In that context, more specialized food gathering techniques might be selected for, and use of technology would be usually selected for and rarely selected against. In the absence of a social contract allowing some kind of “ownership” or exclusive access or possession, most of the well known human technologies are selected against because they require investment and incur great risks.
Many important evolutionary changes involve reorganization of existing features rather than the innovation of a novel feature. That’s probably the clearest way of stating my point.
Another somewhat related point: It is fairly easy to imagine a series of evolutionary changes that would convert a chimp-like common ancestor (of chimps and humans) to a human. However, that would be a senseless exercise because we know australopiths were different in some important ways from both chimps and humans that would never be predicted by such an approach. Thus the linear hypothesis is falsified for most features. I’m not suggesting that anyone is making that error. It is just something that needs to be interjected into any conversation about evolution that seeks to draw conclusions from chimps and humans in comparison or contrast.
Here is a video link, and I might add, a thoroughly unconvincing one–unless of course we include knitting needles and drumsticks as “spears”
http://news.nationalgeographic.....video.html
And thanks for the clarification Jill and Greg…I love the digressions on blidgeons, ramrods,“dentally modified limbic terminus” or a “dagger.”
And yes, I see now the word “spear” is critical to getting Jo Schmo and Jane Roe to care about the plight of these endangered little cousins.Good analysis!