A phenotypic view of evolution Evolution in Structured Populations

Of cultural inheritance and cultural evolution

As you may know, I am writing a book on evolution.  Below is modified from a very rough first draft of part of my chapter on cultural inheritance. 

My thinking about culture has change in that I now think more about cultural inheritance than cultural evolution. The reasoning being that evolution is evolution. It is the change in the distribution of a population due to the gain and loss of individuals. Evolution, and especially evolution by natural selection (if we allow that secular environmental change can be a force of evolution, then arguably this evolutionary force does not require heritable variation), requires that at least a portion of the variation be heritable, but makes no claims as to the cause of that heritability. As such, whether a trait is a physiological trait such as body size, or a cultural trait such as some aspect of a person’s language it is still a component of the individuals phenotype, and it is still organic evolution.

When we are talking about organic evolution we think of individuals (frequently the organism, or the organism and its microbiome), and how the distribution of these individuals change over time. Thus, the population is a set of individuated entities with a phenotype with measurable traits that may change as the individual develops. Because it is the individual living entity (e.g., organism) we can call it biological or organic evolution. In real systems individuals will occupy physical space, and when that space is filled, or the organism is otherwise constrained, and the population can no longer grow it is said to be at its carrying capacity.

However, we would like to have a concept of cultural evolution. Fortunately, the beauty of the concept of evolution is that it can be applied to any system as long as we can identify the individuals and the population. This is what needs to be done to have a useful concept of cultural evolution.

To develop a concept of cultural evolution we first need to identify the individual. We have to remember that ideas or concepts are not fixed entities. In some cases this is almost trivial. It would surprise no one if my interpretation of a poem or song were different than your interpretation. Nor is it surprising that people miss-hear lyrics of songs, such as the miss-hearing of Credence Clear Water Revival’s lyric “there’s a bad moon on the rise” as “there’s a bathroom on the right”. However, there is no reason to believe that my interpretation of the letter A or the wavelength we agree to call the color blue is the same as your interpretation. As long as we agree on the name for the symbol or object we are able to communicate. What this means is that the Dawkins concept of meme is quite meaningless. There is no object that can be identified clearly as a meme. I think the better concept of individual for cultural evolution is the idea as it exists in a person’s mind. Thus, my understanding of the concept of the color blue and your understanding of the concept of the color blue are two different but very similar concepts. Our different understandings of the concept are individuals, and they, along with everybody else’s understanding of the concept of the color blue are analogous to a “species”. The formal definition of evolution I gave is change in the distribution of a set due to the gain or loss of elements of that set. Using this we can define cultural evolution to be change in the distribution of a concept due to the gain and loss of individual understandings of that concept.

Interestingly, the internet the term meme, or internet meme, which needs to be distinguished from the Dawkins meme, appears to be directly analogous to the collection of individual concepts that are closely related. Thus, I would suggest that we use internet meme, or just meme, to describe a set of similar individual concepts that are held by individual humans. That is, meme is analogous to population, and could potentially be substituted for “concept” in the definition above.


Grumpy cat is a classic internet meme.  My understanding of the grumpy cat meme is different from yours or anybody else’s. (from https://jasoninwv.wordpress.com/tag/grumpy-cat/)

In this conception of cultural evolution an individual is a person’s understanding of a concept. Thus, each person is effectively a territory for the concept, and the “population size” of the concept is the number of people in the population. A new individual concept is “born” when a person is exposed to the concept, and dies when the person forgets the concept or dies. Once a concept has been introduced (“born”) it can change within that person over time, however, this is development in the same way that changes in an individual are development when speaking of biological evolution.   An individual concept in a person can change due to simply the person thinking about it, or due to discussions with others. Much of the process of teaching thus, can be seen as introducing heritable changes in the concept a person holds. Importantly, this phenotypic approach allows us to recognize that what we do in learning is to gather information either by observation or being taught and building our own understanding of a concept. That understanding is not transferred as an intact object. Rather the teacher presents their understanding of the concept and the student takes that presentation and makes a similar, but not identical, understanding.

Another recurring theme in this blog is that changes that occur are independent of the name we give it. Thus, if we assign fitness at the level of the organism changes below that level must be analyzed as development, or a related term. In a similar vein, if somewhat orthogonally, if we are interested in the evolution of culture we can treat humans as the “environment” in which cultural concepts “live”, or, if we are interested in biological evolution we can treat the understanding of a concept held by an individual as part of their phenotype, and study the evolution of the human phenotype. The point being that acquisition of a new understanding of a concept by an individual changes both the individual phenotype which can be either development or biological evolution depending on the circumstances, and it changes the distribution of the concept. Thus a cultural change can be studied both as biological evolution and as cultural evolution, the difference being whether the focus is on changes in the organism, or changes in the concept.

The details of the expression and inheritance of a concept will be very different than those of traits and phenotypes in biological systems, thus we can expect the details of cultural evolution to be quite different than those of biological evolution. Nevertheless we can still talk of concepts as having phenotypes or something analogous to phenotypes, and we can talk of a transition equation that describes the process by which a the understanding of a concept in one person gets transmitted to become a new understanding of that concept in a different person. Thus, in broad strokes cultural evolution will be conceptually similar to biological evolution.

There are two areas where the two forms of evolution differ. First is defining the individual.   In biological evolution we defined the individual as the level at which we assign fitness. A similar approach should work for cultural concepts.   But, at least to me as a biologist, identifying a cultural concept where it makes sense to assign fitness seems problematical. There is also the question of how “large” can a cultural concept logically be? As with biological evolution we can assign fitness at any of a number of different levels. One presumes that for cultural concepts a similar set of nested levels could be identified, and logically appropriate levels identified. In any case, whether the appropriate unit for study is classic internet “memes”, smaller units such as the concept of the color blue, or much larger concepts such as the concept of relativity is a question I am not prepared to answer.


Which box is a different color?  The Himba have no problem with this test. (from http://www.iflscience.com/brain/when-did-humans-start-see-color-blue)

The second major difference is in the transition equation.   In biological systems a large portion, and probably in most cases the dominant portion, of the heritable aspects of the phenotype will be due to genetic and cytoplasmic effects. These enter into the system at conception, remain unaltered throughout life, and in many cases will follow discrete Mendelian inheritance rules. In contrast, one suspects that a new understanding of a concept in a person would first occur as a poorly formed understanding, and then develop into a more detailed understanding as the person acquired more information on the topic. Thus, in cultural evolution it seems reasonable to imagine that much of the heritable components of the transition equation will enter well after the understanding of the concept is first formed. Also, unlike biological evolution, it is likely that discrete elements in the transition equation will be rare if they exist at all.

Clearly, much needs to be done to develop the concepts underlying cultural evolution. Just as clearly, a biologist such as myself is not the person to do it.


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