Tuesday, 19 December 2017

Robert Boyd: A Different Kind of Animal

Robert Boyd's new book on cultural evolution is out. It is titled:

A Different Kind of Animal: How Culture Transformed Our Species

The publisher's blurb is here. It says, among other things:

Human beings are a very different kind of animal. We have evolved to become the most dominant species on Earth. We have a larger geographical range and process more energy than any other creature alive. This astonishing transformation is usually explained in terms of cognitive ability — people are just smarter than all the rest. But in this compelling book, Robert Boyd argues that culture — our ability to learn from each other — has been the essential ingredient of our remarkable success.
Google books has it here and offers a peek inside.

The publisher's site says:

Based on the Tanner Lectures delivered at Princeton University, A Different Kind of Animal features challenging responses by biologist H. Allen Orr, philosopher Kim Sterelny, economist Paul Seabright, and evolutionary anthropologist Ruth Mace, as well as an introduction by Stephen Macedo.

There's a review here.

Sunday, 10 December 2017

Evolutionary topology - the M.E.D.I.C.S. framework

I've long sought better ways of explaining and teaching evolutionary theory. A recent novel approach involves evolutionary topology. One approach to applying topological ideas to evolution is to apply it to the histoy of the relationships between the agents involved. This is commonly done when constructing family trees. Here is a set of primitive operations:







The operations are fairly self-explanatory, but some notes may help. To start with, this is a dualistic agent-environment framework. If it isn't clear what the agents are, that's the first thing to sort out. Agents have no properies or attributes - those would be modeled independently. Similarly there is no spatialization - again that would be modeled independently.

"Creation" refers to the construction of agents from non-agents. The most common way that agents originate is normally not "Creation" but "Splitting". An example of creation is the origin of life. However, creation can be more common than this suggests. For example as well as a first organism, there was a first ants nest and a first company.

The framework represents merging and splitting events from symbiology. Splitting is a common evolutionary primitive operation, but the significance of merging was not fully appreciated until the 1960s. Until then recombination was the only "merging" operation most evolutionists considered. Then it became seriously entertained that eucaryotic cells had symbiotic origins. While this endosymbiosis subsequently became widely-accepted science, it didn't have much effect on the foundations of evolutionary theory. Instead it was typically tacked on as an afterthought. Endosymbiosis was considered to be a rare accident during the history of life. Here, by contrast, merging is a primitive operation. It is the time reverse-operation of splitting.

Lastly immigration and emigration are included as fundamental operations. They are listed mainly because they are so important. If you are dealing with a closed system, feel free to reject them.

The framework is an alternative to the "selection-drift" framework, which seems to be one of the main ways in which the concepts of evolution are introduced to people. Selection includes both splitting and destruction, while here those are very different categories.

Historically this framework grew out of my Natural production and natural elimination. I noticed that adding more categories would help to improve the overall clarity. The concept of "evolutionary topology" is not mine. For earlier use see (for example): Topology of viral evolution (2013).

Monday, 4 December 2017

Memetic drift

Genetic drift is a well-established idea in population genetics. It generally refers to stochastic changes in gene frequency that are not caused by selection. The term comes from nautical language: if a ship is not driven by the wind it may "drift" around, pushed hither and thither by the waves. Historically, genetic drift was not considered to be a very important force until the 1960s, when it was shown to be significant experimentally, and it was discovered that many genomes were full of useless junk DNA, which was then subject to genetic drift, resulting in molecular clocks useful for dating evolutionary divergences. Genetic drift results in "neutral networks", whih in turn allow populations to maintain diversity that can be recruited by natural selection if the environment changes. Drift results in historical contingency and path dependence.

Complicating the definition of genetic drift is the desire to distinguish it from genetic draft. The term "genetic draft" refers to gene changes caused by linkage and selection at other loci. It is related to the concept of genetic hitchhiking. Like genetic drift, genetic draft can have a stochastic component, as a gene's neighbours vary over time. Unlike genetic drift, genetic draft can act persistently in the same direction.

Memetic drift is pretty much the exact same thing with memes instead of genes. Like gene frequencies, meme frequencies drift around in the absence of directional selection, resulting in loss of memetic diversity in small meme pools. As with genetic drift, memetic drift is a useful null hypothesis when dealing with the issue of whether an observed trait is an adaptation. As with genetic drift and genetic draft, we can distinguish between memetic drift and memetic draft.

Genetic drift is much discussed but memetic drift is rarely mentioned. I remember a good discussion of it in Kevin Layland's book "Sense and Nonsense". It is sometimes used by researchers as a null hypothesis. However, it is much less frequently mentioned than genetic drift is. This is, I believe, largely caused by cultural evolution's scientific lag. The significance of genetic drift was not recognised until the 1960s. Cultural evolution lags behind its organic counterpart in many ways, and this is plausibly one of them.

If you think about optimization frameworks in economics (one of the most advanced evolutionary social sciences) then the equivalent of genetic drift is rarely mentioned. It is the same with optimization frameworks in physics. Phyics features the "maximum entropy production principle" which explains a good deal of physical evolution. It too has concepts corresponding to genetic drift. However, it rarely mentions or makes use of these concepts. Phausibly, it is because these sciences are underdeveloped relative to evolutionary biology.

I'm generally a critic of contrasting "genetic drift" with "natural selection" (for details see here). Indeed, the definition of genetic drift is relatively complex, and it is often not a very useful scientific category, due to the practical difficulty of identifying it in any particular case. Memetic drift has much the same set of problems. However, I do, of course, acknowledge the significance of evolution by accident, and the systematic loss of diversity in small populations that arises due to factors which don't involve directional selection.

Sunday, 3 December 2017

Quantifying memetic linkage in nursery rhymes

I created my pages about memetic linkage and memetic hitchhiking way back in 2011. However, I haven't seen much in the way of attempts to quantify memetic linkage. To help rectify this I performed a quick study of linkage between lines within nursery rhymes. The aim was to see how the distance between lines altered the chance of them being inherited together. Some results (obtained via Google searches):

Doe a deer

Reference lineTarget lineDocument count
Doe, a deer, a female deerRay, a drop of golden sun394,000
Doe, a deer, a female deerMe, a name I call myself353,000
Doe, a deer, a female deerFar, a long, long way to run296,000
Doe, a deer, a female deerSew, a needle pulling thread180,000
Doe, a deer, a female deerLa, a note to follow Sew116,000
Doe, a deer, a female deerTea, a drink with jam and bread121,000

This old man

Reference lineTarget lineDocument count
He played knick-knack on my thumbHe played knick-knack on my shoe3,290
He played knick-knack on my thumbHe played knick-knack on my knee2,670
He played knick-knack on my thumbHe played knick-knack on my door2,550
He played knick-knack on my thumbHe played knick-knack on my hive2,130
He played knick-knack on my thumbHe played knick-knack on my sticks2,030
He played knick-knack on my thumbHe played knick-knack up in heaven1,630
He played knick-knack on my thumbHe played knick-knack on my gate1,930
He played knick-knack on my thumbHe played knick-knack on my spine1,670

The first thing to say about this data is that memetic linkage is clearly evident, and its effect is quite large.

With genetic linkage, the probability of two genes being separated is roughly proportional to the distance between them, at least for small distances. This is a consequence of the logic of meiosis. However, with memetic linkage, much less linear relationships could be possible - because selection by humans for brevity is involved, and the shape of the linkage curve depends to some extent on how much humans like brevity.

While the data here suggests a fairly linear relationship, we should not expect that result to hold in general. It seems likely that some sets of adjacent memes will have natural "fracture points" where the probability of memes on either side getting unlinked during transmission is high.

A science of memetic linkage is important in advertising and marketing. Many want to attach memetic payloads to existing highly viral memes, in order to spread their content around. That means engineering high memetic linkage. At the risk of stating the obvious, sound engineering ought to be based on good science.


The term "memenomics" seems like an interesting fusion of "meme" and "economics". It seems to have become a brand at memenomics.com. I rather like the word but am less convinced by the associated MEMEnomics book and its "vMemes". That seems more like marketing and self-promotion than science.

I think "memenomics" should just refer to some ground in the vicinity of economic approaches to memetics and evolutionary approaches to economics. "Evolutionary economics" already has a pretty nice name, so maybe "memenomics" could be used to refer to economic approaches to memetics. A nice example of this is the well-known idea of an "attention economy" - where attention is a scarce resource that memes compete to monopolise. That's an example of applying economic thinking to memetics, but there are other ways in which economics could be applied to memetics. For one thing, attention is not the only resource that memes are interested in. They also compete for storage space, transmission bandwidth and various other resources.