Mixing Memory

You’ve probably already come across this story, but just in case:

Oldest chimp tools found in West Africa
Apes could have passed down skills for thousands of years.

In the West African rainforest, archaeologists have found ancient chimpanzee stone tools thousands of years older than the previous oldest finds in the same area. The discovery suggests that chimps may have passed cultural information down the generations for more than 4,000 years.

I’m no archeologist, and since the paper doesn’t seem to be on the PANAS website, as the Nature article says it should be, I couldn’t evaluate the paper even if I were. But if this evidence holds up, it provides an interesting demonstration of one of the key differences between chimp and human culture. Chimps may have “passed cultural information down the generations for more than 4,000 years,” which is impressive, but the information they passed changed very little over those 4,000. The chimps of today, the chimps of 100 years ago (the oldest previous tools were 100 years old),and the chimps of 4,000 years ago were all using basically the same tool to do the same simple job. We humans, on the other hand, exhibit something that Michael Tomasello calls the “ratchet effect.” That is, we not only pass cultural information down from generation to generation, but as a society, or a species, we can improve, little by little, on what we receive from previous informations, and pass those improvements on to the next generation. Thus over time we pass on more and more effective products of culture. That’s why humans have accomplished so much in 4,000 years, while chimps are still using the same tools they were back then. Poor little buggers.

Comments

#1 RBH
February 14, 2007

We humans, on the other hand, exhibit something that Michael Tomasello calls the “ratchet effect.” That is, we not only pass cultural information down from generation to generation, but as a society, or a species, we can improve, little by little, on what we receive from previous informations, and pass those improvements on to the next generation.

“We” is a little ambiguous. Some hominid tool traditions lasted amazingly long — consider that hand axes lasted with only minor variation for something on the order of a million years.
#2 Chris
February 14, 2007

Well, that’s true, not all products of human culture change all that much over time, but many do (even over the periods when some tools weren’t changing), whereas in chimp culture, none do.
#3 CA
February 15, 2007

I’ll take the cultural imprvement seen in the chain saw over a hand axe any time.
#4 Nathan Parker
February 15, 2007

many do (even over the periods when some tools weren’t changing), whereas in chimp culture, none do.

That makes it more of a difference of degree, not of kind. The chimp culture obviously changed when it first acquired stone tools.

It would be interesting to see how much artificially induced culture could actually be maintained across chimp generations.
#5 Brandon
February 16, 2007

That makes it more of a difference of degree, not of kind. The chimp culture obviously changed when it first acquired stone tools.

Strictly speaking, this doesn’t follow; it can only be a difference of degree if the underlying mechanics are the same, and I took Chris simply to be suggesting that the ratchet effect is a bit of evidence strongly suggesting that they are not. That certainly seems to be right. There are, of course, hypotheses on which the this suggestiveness is mere appearance, but that’s not surprising, since it’s true for any evidence — this can happen whenever the evidence is defeasible, which is usually the case; the real issue, I take it, is whether these hypotheses capable of being defeaters are well-founded themselves. That is, the real issue, I take it, is what our evidence for the underlying mechanisms being the same is, and how strong it is on its own.

I think it’s worth pointing out that ‘tool traditions’ are actually extremely complicated, since minor changes in tools can often result in considerable differences in functionality — try using a small lanceolate handaxe to do the same work as a large one, and vice versa. Thus a tool tradition is a very different thing than a tool type; the former being a culturally learned practice of developing and using the latter to optimal effect for one’s practical purposes, given the means available. And clearly when we are talking culture it’s the former (the tradition) rather than the latter (the product) that’s the most important element. For instance, the same cultural products can be produced in radically different cultural contexts — e.g., with the right skills and materials you can hand-make construction paper that’s indistinguishable from factory-made construction paper; but the cultural transmissions required to sustain either process of manufacture are radically different. So a tool tradition may remain constant over a long period of time; but we shouldn’t overlook how much adaptation, diversity, and improvement can go into it even when it is constant.

It occurs to me, Chris, that this ‘ratchet effect’ has a great deal to do with the fact that humans are capable of externalizing their memories, primarily through words and writings. If I recall Tomasello correctly, though, he tends to focus on imitation, which seems a less plausible place to start for understanding the ratchet effect itself. Am I just misremembering? Thinking back, I’m sure I must be misremembering something, even if only by missing some key piece; and my memory is certainly hazy on some parts of Tomasello’s account.
#6 korax@mac.com
February 17, 2007

“Well, that’s true, not all products of human culture change all that much over time, but many do (even over the periods when some tools weren’t changing), whereas in chimp culture, none do.”

“None do?” Kind of a premature statement. We really don’t know this for sure, do we?
#7 john l dennis
February 18, 2007

The key to cultural, intellectual or technological advancement is concepts. Brandon is right when he says, “humans are capable of externalizing their memories”. We do so with spoken and written language. So the ‘smoking gun’ is not tools it is language. And non-human primates do not have language in the formal sense.

There are 4 important properties of language.

1. Arbitrariness – this is a lack of principled relation between a concept and the sound pattern that goes with it.

2. Displacement – this is the fact that the subject of language is not restricted to the here and now.

3. Duality – this is the fact that there are two levels of organization for language – meaningless sounds are transformed into meaningful morphemes and morphemes are transformed (via words) into sentences.

4. Productivity – this is the fact that at each of the levels – sounds into morphemes and morphemes into sentences – that we can produce a larger set (up to an infinite set) of possible combinations.

So what do nonhuman primates have in terms of “language”? I think that you can say that a very limited number of primate calls are arbitrary – but they definitely do not have duality or productivity and an extremely little displacement. What about the primates who have learned sign language? Well, sign language has many iconic symbols – i.e., not arbitrary, and amazingly many of the signs that nonhuman primates have learned are those that are iconic. Coincidence? I don’t think so.

So why didn’t nonhuman primate culture evolve? Because primates don’t have language. Sorry Jane Goodall and Nim Chimpsky.
#8 korax@mac.com
February 22, 2007

http://news.bbc.co.uk/1/hi/sci/tech/6387611.stm

Chimps have been discovered using spears as hunting tools.
#9 korax
February 22, 2007

Again, to state as fact that non-human primate culture has not evolved is presumptious at best. As to whether non-human apes have a “language” depends on how you define language – which has been re-defined countless times, often to segregate human capabilities from those of other animals.

Suggested reading concerning animals “externalizing memories”, displaying “language displacement”, and using native calls that are translated by their peers into a common human/animal communication system:

http://www.greatapetrust.com/research/programs/pdfs/Culture%20and%20Cognition_2_.pdf
#10 Jason
February 23, 2007

The chimps of today, the chimps of 100 years ago (the oldest previous tools were 100 years old),and the chimps of 4,000 years ago were all using basically the same tool to do the same simple job. We humans, on the other hand, exhibit something that Michael Tomasello calls the “ratchet effect.” That is, we not only pass cultural information down from generation to generation, but as a society, or a species, we can improve, little by little, on what we receive from previous informations, and pass those improvements on to the next generation. Thus over time we pass on more and more effective products of culture. That’s why humans have accomplished so much in 4,000 years, while chimps are still using the same tools they were back then. Poor little buggers.

You’re making an unwarranted assumption about the limitations of chimpanzee culture from a comparison that fails to consider the appropriate timescales. 4,000 years is nothing. Anatomically modern humans seem to have been around for at least 100,000 years, but for most of that time our technology was limited to simple stone tools. I remember reading about one site where anthropologists uncovered human stone tools that were essentially unchanged over a period of 40,000 years. So the chimps aren’t looking so bad by comparison.