Monday, February 2, 2015

Some Quick Thoughts on Cultural Evolution

Here are some thoughts I’ve been having on cultural evolution. All of them need fuller exposition, but I don’t have time for that now.

1. Cultural Evolution, so What?

I’ve got a fairly sophisticated narrative account of some varieties of popular music in 20th century America. The account centers on the interaction between African- and European-American populations and musical forms. When I was doing that work–in the late 1990s–I kept thinking that this is the kind of phenomenon that begs for an account in terms of cultural evolution. But I didn’t once use the term “memes” (my term of choice at the time) in the paper nor did I talk of cultural evolution (except in passing at the very end). It’s not at all obvious to me how any existing account of cultural evolution would lead to a deeper understanding of that history. It would just be an exercise in terminology mongering.

This is a very big deal for me, and I don’t yet know what to do about it.

2. Information and Apple Pie

On information, sure, at the highest level of generality and abstraction cultural evolution involves information. But that doesn’t get us much in itself. Until we understand how that information is embodied in the brain and in various media and can measure it, the idea isn’t a very useful or deep one. It’s one of mere terminology, verbal packaging. But see comment six, below.

3. Information, DNA, the Brain and the Rest

In biology we know that genetic information is embodied in DNA and we know a great deal about how that works. And we are rapidly increasing our ability to manipulate DNA.

We don’t know how information is encoded in the nervous system. But that’s not so much my point here. It belongs in #2 above.

My point here is that, in long-held view, the genetic information for culture isn’t in the brain. It’s in publicly accessible traits of physical objects and processes. That means that, whereas the genetic information of life forms is encoded in the same medium, DNA, that is not the case for cultural genetic information. The genetic information for culture has various embodiments.

From the standpoint of theoretical elegance/parsimony, this is not so good. But the fact is, no matter what kind of model you choose, if you want to deal with information, you are going to have to deal with multiple physical embodiments and the transformations between them.

4. Mutual Information for Culture

We’re interested in the ‘conservation’ of information in the social group. That requires shared access to common reference points. The meaning of those reference points is, in effect, negotiated through interaction. Those agreed reference points are the ‘genes’ of the cultural process.

Compare this with DNA replication. The double strand divides and then each half constructs the necessary complement. The result is two identical DNA molecules where there had been one.

Shared access to a common public reference plays the role in cultural informatics that DNA replication plays in biological informatics.

On mutual information in culture, see my Open Letter to Steven Pinker.

5. The mind as computer program

Programs have variables and variables require values. Where do mental programs get values for their variables? Some of them are generated internally.

And some of them come from the external world. Among those we have the cultural genetic material. They function as values for variables in mental programs.

See this post for further specification of this thought: Memes as Data: Targets, Couplers, and Designators. That is collected in my working paper, Cultural Evolution, Memes, and the Trouble with Dan Dennett.

6. A somewhat longer thought on information and its transformations

This is a comment in reply to Tim Tyler on a post from last week, Cultural Beings & Intertextuality; Information.

I've been thinking about this and, sure, information. Why not? But at that level, what can you do with the idea? It's pretty much mom and apple pie. How can you operationalize the concept to solve real problems? That's what Shannon and Weaver did for a certain range of problems, a range of problems that turns out to be large and useful. But no one's been able to operationalize a version of information that allows us to study the meaning of language strings. While language doesn't cover all of culture it covers quite a bit, so, if you want an informatic account of culture, you're going to have to come up with an informatic account of language. Without that, claims about culture as information are mostly smoke and mirrors, hand-waving and tap dancing.

This passage in van Baalen's article [reference below] struck home for me:
Presenting his views on Dawkin's [36] notion of genes as units of evolution, Williams [50] made the important point that we should separate the physical manifestation of genes from their information content. Evolution, Williams argued, takes place in the information domain, or the ‘codical domain’ as he called it: information gets transmitted and DNA molecules eventually perish. What I wish to argue here is that this insight not only applies to genes, but should also be extended so as to incorporate all of the evolutionarily relevant forms of information: genes but also epigenes, genes from symbionts, various forms of experience, culture and so forth. In this information-based view, individuals (units of adaptation) are merely bundles of information.

This does not mean that physical form becomes irrelevant. On the contrary, the physical aspects of an information carrier determine its dynamics, through its capacity for change, storage and transfer. Different sources and origins of information may have very different kinds of dynamics indeed: some of my genes contain very ancient information, whereas my brain contains extremely recent (and mostly ephemeral) information [6]. The physics of a given carrier may have an effect on interpretation of the information it contains.

To us, the physical support of a message contributes to its meaning because it helps us to interpret it. If we were to encounter a piece of text in an unknown script, we would tend to guess its message differently if the text were hewn in a stone monument than if it were merely scribbled on a piece of paper. In a biological context, a sequence in DNA does not mean the same as the equivalent sequence in RNA: many sequences in DNA are not transcribed and thus potentially irrelevant, whereas an RNA sequence is more likely to be relevant because it has been transcribed, and therefore linked to some particular environmental conditions. Danchin [6] calls the physical manifestation of information its ‘avatar’, which is a generalization of the concept of phenotype [51].
You mistake my intransigence on the this point. I long ago entered the world in which one talks about information as a general phenomenon that applies in a wide range of cases. I don't need to know that. That's mom and apple pie and the flag all wrapped up in a bundle.

I'm interested in the various physical embodiments of information and the mechanisms by which information is conserved as it "flows" from one physical embodiment to another. Dan Dennett, it seems to me, is still living in a world where information is a new idea, a wonderful new information. Dennett hasn't yet absorbed the information epiphany; it's not yet percolated down into his conceptual bedrock.
Information, wow! You mean it's the same whether it's in a brain, or ink splotches on paper, or electrons through a wire, or vibrations in air? That's powerful stuff. Information isn't physical. It's well, it's information!
But it is always embodied in some physical medium. It is an attribute of that medium as approximate roundness is an attribute of an apple, or even mass. Understanding those physical embodiments and how they interact, that's where the game is these days.

* * * * *

van Baalen M. 2013. Biological information: why we need a good measure and the challenges ahead. Interface Focus 3: 20130030.


  1. Information theory is pretty general. It already covers the transmission of linguistic messages - just as it covers messages relating to music, science, technology and religion. What it doesn't cover is "meaning". However, complaining that information theory doesn't cover "meaning" is rather like complaining that a ruler doesn't tell the time. Sure - but that's not what it's for.

  2. But it's the meaning of those messages that is culturally important. And when Dennett talks about words as memes he quite definitely talks about their meaning. I've also seen a video where he says that memes aren't about Shanon/Weaver information, they're about "semantic" information. So if information can't deal with meaning, then it can't deal with culture in any deep way.

    The ruler analogy is not a good one. Rulers measure one kind of physical property and have units of measure, typically in metric or English terms. But it's not time. You need something else for that. And time has its own units of measure. The concept of Shanon/Weaver information can be used to develop units of measure for rather peculiar physical properties that are identified in the relationship between a source, a signal, and a destination. In each case we have units of measure. But we don't yet have units of measure for meaning.

  3. So: information theory is useful in genetics/memetics - despite not having anything to do with meaning - largely because it deals with the topics of mutual information and error correction/detection. Mutual information is probably the single most important concept. That lets observers see when a gene is probably a copy of another gene (or they are both inherited from a shared ancestor). There are all manner of tools for building phylogenetic trees from analysis of bulk genetic data which are based on finding such similarities. Reconstructing family trees is a key activity for evolutionists. The fact that these tools work on the level of information means that they can also be applied to cultural evolution without modification. The exact same tools can be used to construct phylomemetic trees. Information theory thus unifies the foundations of organic and cultural evolution.

    Tools for handling meaning might be interesting. However that risks getting onto the messy topics of neuroscience and machine intelligence. The chance of getting a neat theory there seem correspondingly smaller. However, knowing about existence of tools we don't yet have is no reason to fail to appreciate the tools we do have. Those tools are very useful and do a lot of good work.

    1. Reconstructing family trees is a key activity for evolutionists. The fact that these tools work on the level of information means that they can also be applied to cultural evolution without modification. The exact same tools can be used to construct phylomemetic trees. Information theory thus unifies the foundations of organic and cultural evolution.

      Interesting. As you know there is quite a bit of empirical work on cultural evolution and a lot of it is about inferring phylogenies. The people who do this work don't seem to care much whether or not the entities they're counting are memes or whatever, nor do the worry what happens inside people's heads and the relationship between that and artifacts. Nor should they, at least not yet. They want to count things, note distributions, and look for relationships. All of which is intersting and important work.

      Tools for handling meaning might be interesting. However that risks getting onto the messy topics of neuroscience and machine intelligence.

      Yes. I'm interested in seeing how far we can go without having to deal with those messy topics. Those messy topics happen to interest me a great deal, but I don't want to have to depend on getting those things worked out because that's going to take quite awhile.