Friday, 27 June 2014

Tim Tyler: Darwinian physics

Transcript:

Hi. I'm Tim Tyler and this is a video about Darwinian physics.

In the 1980s there was a movement to incorporate elements from physics into evolutionary theory. It was claimed that not all of the complex-looking patterns of organisms were there in order to benefit the genes of their owners. Instead, some of them were the product of self-organizing systems. Reaction-diffusion patterns were invoked to explain zebra stripes and cheetah spots - challenging the idea that these were adaptations whose purpose was to improve camouflage. Cellular automata were found that reproduced the decorative patterns found on some seashells. The branching tree-like pattern that is found everywhere in biology was likened to dendritic frost patterns, electrical discharges and propagating cracks. The search was on for the new rules that governed these self-organizing systems.

Now, we have found many of these rules. A big and important one has turned out to be: Darwinian evolution via natural selection. So, now the time is ripe for Darwinism to claw back some of the explanatory territory that was lost to complexity theory - and it is time for it to perform some invasions of its own - into realms that have been traditionally occupied by physics and chemistry.

Darwinism is based on processes involving copying with variation and selection. It was once widely thought that copying of the required kind was unique to biological systems - and that before the origin of life copying fidelity was too poor to support any kind of Darwinian evolution - with any copying processes producing instead an error catastrophe and a mutational meltdown. This argument was made by A. G. Cairns-Smith in 1982 - for example. However, this idea has turned out to be dramatically wrong. It turns out that the high-fidelity copying suitable for supporting cumulative adaptive evolution is ubiquitous in simple physical systems.

Lightning strikes are one of the easiest examples of Darwinian physics to visualize. Lightning makes a branching tree. This is a family tree - with regions nearer to the trunk being the ancestors of regions nearer to the tips. If you ask what information is transmitted from parent to child in this case, the answer is that the offspring inherit their parent's position. They inherit this extremely precisely - down to the nearest millimeter.

Position isn't the only thing that is inherited in this way, other attributes - such as velocity and chemical composition - are inherited too, although this inheritance is often less precise.

Examples of Darwinism in simple physical systems are ubiquitous. Most tree-shaped structures are the product of copying with variation and selection. This includes many crystals, fractal drainage basins, propagating cracks and electrical discharges. Re-radiation of photons after hitting dust particles is one of the most common events in the universe and it follows the classical Darwinian algorithm - producing a family tree of photons with the older photons with higher energies being ancestral to their more numerous, but less energetic offspring.

Many other cases do not so obviously exhibit a simple tree. For example, raindrops divide, but they also join creating a network - rather than a classical phylogenetic tree. Of course there are also broadly similar examples of joining in classical evolutionary biology: gametes fuse together, parasites inject DNA into hosts, bacteria assimilate other bacteria and lineages join forces in symbosis. Evolution involves joins and mergers as well as splitting and subdivision.

In other cases, the phylogenetic tree is only visible if you take a historical perspective. For example, every asteroid has an associated ancestral tree of other asteroids, moons, planets and stars that it was formed from. However, you don't see the tree by looking at the asteroid. Only if you look back in time does the family tree become visible.

It's well known that organisms can be modeled as optimizing a fitness function. The same thing applies to lightning - it too is optimizing a function. It acts as a crack in space the seeks out the path of least resistance in its search for the ground. The fact that organic evolution acts as an optimization process is widely exploited by genetic algorithms. There, humans allocate a fitness function and let simulated evolution do their optimization work for them. Optimization features maximands - and these give evolution an apparent teleological character. Biologists can ask what wings are "for" - and then give a reasonable-sounding functional answer. Darwinian physics brings the concept of adaptation to the evolution of inorganic systems - and it becomes reasonable to ask what their features are "for".

Ultimately, both living organisms and lightning strikes can be modeled in the same optimization framework using the same maximand - by treating them both as maximizing entropy.

Entropy maximization is a formulation of optimization processes from within physics which some physicists are already familiar with. Some might ask what the advantages are of taking a Darwinian perspective over one based on entropy maximization. This is a complex question which risks going beyond the scope of this video, but briefly, entropy maximization and Darwinian evolution are largely equivalent ideas which make most of the same predictions - since nature's maximand is closely correlated with entropy production. These are mostly two different ways of looking at the same phenomenon. However, it is possible to select locally for other things apart from entropy maximization - including entropy minimization. Path dependency within a Darwinian framework provides a context which helps to explain these apparent deviations from maximum entropy production.

Lastly, Darwinism neatly explains observation selection effects. While these have long been considered to be part of physics, they are obviously a case of selection acting on observations. We can reformulate the concept of survival of the fittest as observation of the observable. This more general concept acts as a grand unified theory of selection - which neatly covers both Darwinian evolution in biology and observer selection effects in physics and many other areas of science.

Over the last two centuries, Darwinism has had a revolutionary impact on biology, leaving most of the theories that preceded it in the dust. Physics and chemistry are relatively new and unexplored frontiers for Darwinian explanations - but it seems clear that incorporating Darwinism into physics will involve some rewriting of textbooks, and a fair number of psychological paradigm shifts, as scientists gradually awaken to the idea.

Historically, Darwinism has had a hard time penetrating areas that go beyond inheritance of nucleic acids. For example, cultural evolution is still a topic mired in confusion and controversy. However, physicists are supposed to be intelligent people. Hopefully they will prove to be more open to Darwin's ideas than many social scientists have been - and less inclined to treat the Darwin enthusiasts as hostile invaders.

Enjoy,

References

Friday, 13 June 2014

Cultural somatic selection

The term "somatic selection" refers to selection within bodies. It's used to refer to the way that somatic cells face different selection pressures from germ-line cells. If you trace your cell lineages backwards in time, the ancestors of your cells were almost all germ-line cells. Only the most recent ones played the role of somatic cells. These cells are in a radically different environment from the one all their ancestors - and face different selection pressures.

Something similar happens with mitochondria in males. All the ancestral mitochondria were in female germ-line cells. The mitochondria of males find themselves in somatic cells for the first time, and they experience maleness for the first time too.

This difference in selection pressures is a result of "germline sequestration" - the separation from before birth of somatic cells from germ line ones. In many plants, there is no such separation. Many somatic cells remain totipotent. For example, in strawberry plants, most somatic tissues can go on to form runners or seeds.

Another closely related case arises with parasites. The ancestors of a parasite all spread from one body to another. However, inside a body they face different selection pressures from the primary ones that molded their ancestors. There, what pays is doing well inside the body. Something like generating itchy scabs may be counter-productive in this context - since it just activates the host immune system. Within bodies there's often selection against between-host transmission, and for better exploitation of the host resources. It might be a bit of a stretch calling this "somatic selection" - since the soma involved is the body of the host - but the process involved is essentially the same.

This brings us to cultural evolution. Memes face similarly dual sets of selection pressures. The ancestors of memes all spread between minds - but once inside a individual mind they face selection to survive and reproduce within that mind. In that competition, the selection pressures are different. Once inside a mind, there's a local competition for attention - and in that context, efforts expended on spreading between minds turn into a waste of resources.

In the organic case, a common consequence of this type of selection is the rapid evolution of avirulence within individuals. Persistent viral infections gradually become asymptomatic - not because they have gone away, or because the immune system gets better at combating them - but because they evolve away from the ancestral virulent type under the selection pressures within the body - which favour other traits.

I expect that that this happens with memes too. There are some confounding factors with memes - since things like news-related memes are time-sensitive and naturally lose their virulence over time anyway. However, some memes are more 'timeless'. One candidate for this effect is religious evangelism. This theory would be consistent with the idea that levels of evangelism will gradually decline - after an initial indoctrination period. In the secular world, evangelism associated with causes and charities may well behave in the same way. In general, this theory predicts that people are more likely to teach others things shortly after learning them - and that this should be especially true of material with 'evangelical' content.

The idea that 'old' infections lose their ability to cause pathological symptoms associated with their transmission raises some theraputic possibilities. For example, maybe you could relieve the symptoms of warts by putting some virus from an old person into a young person using a syringe. In fact, we already do something similar to this with vaccinations. A closely-equivalent cultural practice would appear to be organised education - which systematically transfers memes from the old to the young. However, education isn't specifically about combating the effects of bad memes.

Of course, the idea of fighting bad memes with good ones is not new. We use the same principle whenever we consume probiotic products containing live bacterial cultures. However, cultural somatic selection proposes a specific place to look for the good memes: old people. Particularly old people who once showed symptoms, but who are now asymptomatic.

Tuesday, 10 June 2014

Cultural lag is adaptive lag

The term cultural lag refers to the notion that culture takes time to catch up with technological innovations. It is an old and well-established phenomenon.

Cultural lag is a form of adaptive lag - and adaptive lag is a common feature of co-evolving systems. Overall, it seems like a nice correspondence between cultural and organic evolution.

Just as Darwin sought evidence for organic evolution in its imperfections, so imperfections in cultural evolution are fertile ground for those following its tracks.

Boyd and Richerson's cultural evolution vs memetics

Boyd and Richerson's conception of cultural evolution seems to have become on of the most popular ones in academia. It is one of the closest theories to memetics that academics have come up with. As it (correctly) says here: "the biggest difference is a difference in academic lineage". I've written various articles contrasting their views with memetics as I understand it. However, this seems like time for a summary post. Here are what seem to me to be the main "sticking points":

  • Terminology. Boyd and Richerson use "cultural variant" while memetics uses the "meme" terminology from Richard Dawkins. "Cultural variant" hides the link to biology in a manner apparently designed to appeal to anthropologists. With "meme" the link to biology is up front and central. As far as I can tell, the terms are functional synonyms - though "cultural variant" is a lot more long winded and a lot less popular.

  • Boyd and Richerson seem to see many more differences between cultural and organic evolution than memeticists do. For details of this see the differences remain exaggerated article. To memeticists, Boyd and Richerson seem to not understand the parallels properly. That matters, because understanding the similarities and differences is one of the primary points of the scientific effort to study cultural evolution.

  • Boyd and Richerson have put a big focus on gene-meme coevolution. By contrast in memetics, genes typically change too slowly to be worth considering, and the main focus is on the evolution of memes. A related difference is that Boyd and Richerson have mostly been considering events many thousands of years ago. Memetics generally has much more modern concerns. Gene-meme coevolution is a much more complex, difficult and poorly-understood topic than memetic evolution is. Many academics became obsessed with it in the 1980s. It was not a particularly positive obsession. It was rather like trying to fly before you could walk. Impressive, but not terribly sensible.

  • Memetics is symbiology-rich. Boyd and Richerson have written a little about symbiology in cultural evolution, but mention it rarely and seem to regard it as an analogy. To a memeticsist, their work often appears to be symbiology-challenged.

  • Boyd and Richerson are long-standing supporters of group selection. By contrast, I - and probably most other evolutionists - prefer to look at evolution in terms of kin selection. Group selection appears to have led Boyd and Richerson astray. For example they argued in their 2005 book that group selection did not have a significant effect on human DNA. Now that the equivalence of kin selection and modern forms of group selection is widely understood, this claim appears to be unsupportable.

  • Memeticists tend to be Darwinian revolutionaries. By contrast, Boyd and Richerson do not seem to be revolutionaries. Instead, they say:

    We believe that the Darwinian theory of cultural evolution will make contributions across the broad sweep of problems in the human sciences, but the project is one of introducing additional useful tools and unifying concepts rather than an imperial ambition to replace great swaths of existing theory or methods.

    They even contrast their "better mousetrap" with Dennett's "Universal acid". I remember that one of my thoughts on reading "Not by Genes alone" was: how do they make this revolutionary material seem so dry?

On a slightly more positive side, by persistent efforts, Boyd and Richerson appear to be managing something memetics has yet to achieve - namely making cultural evolution respectable in academia. There's still a long way to go here, but their efforts here are welcome.

On the other hand, if it wasn't for them, maybe we would have some real memetics in academia - instead of a feeble and watered-down version apparently designed to appeal to anthropologists. As vocal opponents of memetics, Boyd and Richerson may well have a lot to answer for. I think most students of memes have ambivalent feelings towards their work.

We still need a strong version of memetics to be championed from within academia. My current expectation is that the promise of cultural kin selection will help to open the flood gates on a meme-oriented view of cultural evolution - broadly mirroring what happened with kin selection and genes in the the organic realm in the 1960s and 1970s.

References

Monday, 9 June 2014

Mark Ridley's definition of "Evolution"

Mark Ridley's "Evolution" textbook excluded three forms of change from its definition of "evolution". These were:

  • Changes during development;
  • Ecosystem changes not affecting gene frequencies within species;
  • Cultural changes.

Excluding cultural changes is obviously contrary to the spirit of this blog - but I have come to realize that these other exclusions are equally invalid. Changes during development count as evolutionary - most obviously the development of the immune system and individual learning are conventional Darwinian evolutionary processes. Lastly, I think that ecosystem changes should count as evolution too. It is true that some define evolution to be changes in relative gene frequencies. However, in practice it really matters whether your population size is two or two million.

Part of the motivation for excluding such processes from evolutionary theory appears to have been to help make evolution a scientific theory, capable of being refuted. If all change is classified as being evolutionary, then no observations can refute the concept - and the term "evolution" becomes a redundant synonym.

However, it seems to me that there is a better candidate for the role of making evolution a testable concept: the requirement that evolution be consistent with physical law - that it proceed without miracles.

Excluding cultural change, developmental change and ecosystem-level changes from the evolutionary process unnecessarily victimizes and diminishes those processes. Evolution ought to be defined in a manner consistent with Occam's razor. A laundry list of excluded topics is not appropriate.

Sunday, 8 June 2014

Repology 101: Copying is ubiquitous

Copying is everywhere in biology. It is most obviously seen in DNA replication. Electrical signals are copied inside brains whenever an axon branches. Ants copy each other's paths by following pheromone trails. Copying is also the foundation of all human culture. It's reached a zenith inside computers and on the internet.

What is less widely appreciated is that copying is also ubiquitous in inorganic, non-living systems. Ripples, flame propagation, crystal growth, electrical discharges, propagating cracks, and photons hitting dust all involve copying. Copying is a fundamental part of physics. It is built into the fabric of physical law.

While there's been a science that studies copying (and some other things) in living systems (genetics) there's been little or no scientific focus on copying outside biology. It has been a dark area of science.

Repology 101: Repetition

It would be quite nice to say that repology is the science of copying - covering reproduction, replication and repetition. However, repetition is a bit of an odd-one out here - it doesn't necessarily involve copying.

Of course many types of repetition do involve copying. Any type of repeating voluntary animal behaviour, for example, involves repeated copying of information from memory neurons to motor neurons.

However, there are some types of repetition which do not involve copying - for example: spinning objects repeat their earlier configurations repeatedly - yet typically nothing is being copied during the process.

The phenomenon of repetition brings the domain of repology into question. The term 'reps' is often used as an abbreviation for 'repetitions' - raising the question of whether repology should include repetition.

I think we are better off with repology being the science of copying. Copying if of significant scientific interest - since it is part of the foundations of genetics and evolutionary theory. Repetition that doesn't involve copying seems to be a quite different topic. I think it is worth excluding it.

Saturday, 7 June 2014

Attractor? You keep using that word...

I've criticized the (bad) Claidiere/Sperber 2014 paper here recently - in my article titled: Is cultural evolution different because it is constructive?

This post goes after the paper's basic terminology. The paper defines the term 'attractor' to mean:

We can then characterize an attractor as any type whose relative frequency tends to increase over time.

This is a terribly broad definition of 'attractor' - and it is nothing like what the term is usually used to mean in complex systems theory. This is what the term "attractor" usually means:

In dynamical systems, an attractor is a set of physical properties toward which a system tends to evolve, regardless of the starting conditions of the system. Property values that get close enough to the attractor values remain close even if slightly disturbed.

I do not see the rationale for redefining 'attractor' to mean: anything that is subject to a relative increase in frequency. 'Attractor' is an ordinary English word - as well as an existing technical term. No matter how you cut it, it just doesn't mean anything like what Claidiere/Sperber say it means.

There's a long tradition of people using the term 'attractor' in its standard sense from complex systems theory in biology while talking about adaptive peaks on fitness landscapes. For example, look at the work on N/K fitness landscapes. I see no reason whatsoever to mess up this situation - by redefining a standard term to mean something counter-intuitive and confusing.

The Claidiere/Sperber definition of attractor is not just non-standard - it seems to be of no practical use. Defining an attractor as: "any type whose relative frequency tends to increase over time" makes anything decreasing in frequency slower than the fastest-decreasing type into an 'attractor' (relative to that most rapidly-decreasing type). What's the point of that? It seems practically useless as a classification scheme. Almost every type becomes an 'attractor'. The standard definition of 'attractor' doesn't suffer from this property - where practically everything is an 'attractor'.

Lastly, I am generally opposed to characterizing biological systems as subject to attraction - without making any mention of repulsion. Attraction-only dynamical systems are well known – e.g. gravitation. However, there are also dynamical systems with attraction and repulsion – e.g. electromagnetism. Repulsive selective forces are well known in biology – e.g. “divergent selection”. So: evolution is more like an electromagnetic system than a gravitational one in this respect. We probably don't want 'attraction-only' treatments of evolution becoming common - people will just get confused by them.

Thursday, 5 June 2014

The appeal of generality

With articles like:

...to my name, readers might guess that I think that generality is a virtue in scientific theories. Why is generality a virtue?

  • General theories explain a lot of facts with little theory - satisfying Occam's razor;

  • Society slices science up into specialist-sized pieces. These are unevenly distributed - and much of value falls down the cracks between the theories. General, broadly-applicable theories are an attempt to compensate for this flaw.

I think that's about it. The systematic neglect of general theories by others might also be a contributing factor.

Cultural divergent selection

Divergent selection is selection which pushes traits in different directions in different sub-populations. Selection on gamete size is a classic example - if large gametes (eggs) do well and small gametes (sperm) also do well, then divergent selection will force these traits apart and eliminate gametes of intermediate size.

Divergent selection is often invoked in cases of speciation. If two incipient species come into contact under circumstances where they can interbreed, but the hybrid offspring have reduced viability (due to crossover recombining incompatible genes) then divergent selection will favour traits that allow the individuals to avoid interbreeding.

The most obvious case of divergent selection in cultural evolution involves divergent selection for tribal markers. If individuals in groups benefit from interactions with ingroup members, and are harmed by their interactions with outgroup members then traits that help to distinguish ingroup from outgroup can be favoured. This results in divergent selection on cultural variation that distinguishes the groups - and this works to drive the groups apart - into different tribes with different cultural tribal markers.

It is interesting that the logic of this is very similar to that given for the case of two incipient species. In both cases, ingroup interactions are favoured, while outgroup interactions are punished. Divergent selection on human tribes can be reasonably expected to sharpen tribal boundaries, and to increase the frequency of tribe formation.

It has previously been widely speculated that memes increase speciation rates. There's evidence for this in songbirds, for example. Cultural divergent selection illustrates one part of the mechanisms that are probably involved.

Wednesday, 4 June 2014

On the alleged "self-domestication" of humans

There are a lot of articles out there that claim that humans are a self-domesticated species. It is certainly true that modern humans show many signs of domestication. Humans are domesticated creatures. At first glance there is no other dominant species around to do the domesticating - thus the popularity of the "self-domestication" concept.

In this article, I will argue that institutions and organizations act as powerful masters to humans, and act as the agents responsible for the domestication of modern humans. The idea of institutions and organizations as domesticators renders the "self-domestication" hypothesis largely redundant.

Institutions and organizations are largely cultural phenomena. Some employers make their humans into replaceable components, making their essence primarily cultural. By contrast, some organizations are personality cults - where a single humans forms an essential component. Overall, although institutions and organizations typically have both organic and cultural components, the cultural element is often very significant. It is common for modern organizations to actively eliminate dependency on any individual humans.

Similarly, human responses to domesticating forces are also largely cultural. Modern humans are domesticated in a way that cavemen are not. Maybe cavemen are a bit domesticated - compared to chimpanzees - but it is mainly cultural responses to cultural forces that compose the phenomenon under discussion.

Institutions and organizations can often be very powerful, compared to individual humans - making them worthy domesticating agents.

Presumably, critics might claim that institutions and organizations have only been substantial sources of human power for the last 10,000 years - and that in hunter-gatherer tribes human personalities were a more dominant force. It is true that institutions and organizations weaken in power (relative to individual humans) the further back in time you consider - but they would still have had considerable power 10,000 years ago. Also, quite a bit can happen on that timescale - including quite a bit of human genetic evolution.

Another comment by critics might be that within institutions and organizations there's often a chain of command - where increasingly powerful humans monitor and manage those beneath them, while reporting to those further up the chain. So even within institutions and organizations, there's always a more powerful human immediately above any individual - who can act as the domesticating agent. That may be true, but if you ask where the power differential comes from in the first place, it comes from the institution itself. Without that, the whole structure collapses.

The humans-as-a-self-domesticated-species meme seems to have some momentum behind it. However, science isn't a popularity concept. While humans show many signs of domestication, a failure to understand cultural evolution has led to a misidentification of the domesticating species. Modern humans have been domesticated largely by institutions and organizations - which have their own inheritance mechanisms and lineages that are independent from those of humans. Saying that humans are "self-domesticated" totally misses this important point.

References

Tuesday, 3 June 2014

The cultural founder effect

The founder effect describes dynamics where a partly-isolated niche is invaded by a small number of immigrants, whose descendants go on to dominate the niche. The offspring population often exhibits reduced genetic diversity.

The founder effect is about equally applicable to cultural and organic evolution.

Often the easiest places to observe the founder effect is on isolated islands. They represent a kind of natural microscope for students of the founder effect. Australia, New Zealand, Iceland, Japan, Tasmania and Madagascar are all places that exhibit both genetic and cultural founder effects.

Cultural founder effects can be seen in large organizations that grow from small ones. Often the founders of organizations have unusual ideas of various kinds - which they sometimes go on to impose on the corporations they end up directing. Apple and Microsoft are both famous examples of this.

Founder effects are also seen in products. The Xerox copiers, Coca-cola, The Sony Walkman, and the Apple iPhone are product lines that started with single product, and then subsequently underwent substantial proliferation. If you are the first to market with a product in a new niche, the changes are good that you will launch the second and third products in that space as well.

Cultural evolution exhibits what is known as the serial founder effect as well. This takes place when there's a string of founder effects, one after the other. For example, we can see this when there's a chain of companies founding new start-ups from existing employees - and existing corporate culture.

The cultural founder effect is an important effect to understand when considering product development. Since the descendant of cultural founders can monopolize product niches for a while, creating cultural founders is the aim of many, and identifying cultural founders is valuable to investors and trend spotters.

Monday, 2 June 2014

The "third way" of evolution?

A new web site devoted to "new thinking on evolution" has been launched. It's titled "The Third Way". It bills itself as follows:

The vast majority of people believe that there are only two alternative ways to explain the origins of biological diversity. One way is Creationism that depends upon supernatural intervention by a divine Creator. The other way is Neo-Darwinism, which has elevated Natural Selection into a unique creative force that solves all the difficult evolutionary problems. Both views are inconsistent with significant bodies of empirical evidence and have evolved into hard-line ideologies. There is a need for a more open “third way” of discussing evolutionary change based on empirical observations.
Comparing Neo-Darwinism with creationism seems likely to irritate supporters of the former.

At the moment, the site apparently mainly consists of a list of people and a list of books.

It seems a bit disappointing. Surely the biggest current revolution in Darwinism is the expansion of its domain - to cover physics, chemistry, culture and other domains - often referred to as "Universal Darwinism". That revolution apparently gets no coverage on the site. If you compare their book list with my Universal Darwinism book list, there's no overlap.

It seems as though they are missing the revolution.