My preoccupation with cultural robustness and evolvability has naturally caused me to think frequently about the problem of cultural inheritance. If we take a broad definition of culture to be non-genetic, non-epigenetic information that is socially transmitted, then culture becomes a Darwin machine like any other. For those unfamiliar with the term, a Darwin machine is any iterative process in which heritable variation is generated and subsequently undergoes some sort of selection. The components necessary for creating a Darwin machine, then, are variation, selection and inheritance.
Note that this formulation is substrate neutral. In other words, it does not depend on what the media of variation, selection and inheritance are. Although the specific details will change, the same general logic applies whether we are talking about genetic systems, certain kinds of evolutionarily inspired computer algorithms or, presumably, culture. This makes the notion of a Darwin machine potentially quite powerful in its ability to describe and understand many different kinds of systems from within a common framework. Unfortunately, though, there remains much work to do in order to realize this potential. In particular, to become more broadly applicable the individual components that make up Darwin machines must also be framed in substrate neutral terms.
To take but one of the necessary ingredients into consideration, how could inheritance systems be framed in substrate neutral terms? To begin to imagine this I think it makes sense to start by considering the necessary components that make up the system we understand best, the genetic inheritance system. So thoroughly studied has this system been that a central dogma has arisen around it that describes the flow of information within cells. This flow begins with information storage in the form of DNA. Almost every cell within a body contains a complete copy of all the genes necessary to build and maintain the organism. However, not every gene is expressed at every moment. Indeed, timing is critical for many cellular processes and so cells have evolved mechanisms to determine which genes should be turned on and off at specific times in response to environmental signals. Once a gene is turned on, it is transcribed into an RNA intermediate which is, most often, translated into a protein product that performs some important function for the cell, be it structural, regulatory or metabolic.
At some level, carving this system up into essential components is a bit arbitrary. Nevertheless, I think some general themes do emerge. For instance, it seems an important component is some kind of information storage system. Obviously, for inheritance to occur there must be some way of transmitting this information to new entities. At the same time, there needs to be an information retrieval system and a crucial part of this information retrieval system would seem to be way of "reading" the environment to "know" what information is required and when it is needed.
Are these the minimal necessary components? Would they be sufficient to establish an inheritance system? Are all of them needed? Are there other components missing from this list? I would very much like to see more discussion along these lines and I welcome any insights others might have.
I recently had someone tell me that there was no need for new, substrate neutral terms. He felt that genetic inheritance provided a sufficiently broad framework and that it could easily be expanded to accommodate other kinds of systems. I think this is a mistake for at least two reasons. First, I worry that using genetic terminology predisposes researchers to only look for the familiar. While there are undoubtedly similarities in cultural and genetic inheritance systems, there are just as assuredly significant differences as well. Foregrounding future work with genetically laden conceptual frameworks makes it likely that at least some of these differences could be completely overlooked.
Second, I believe that taking a step back to look at inheritance from a substrate neutral perspective produces new questions and opens space in which to explore them. For instance, if it is true that an inheritance system needs some form of information storage then an obvious difference between genetic and cultural evolution is that the former contains information in a relatively concentrated from while the latter uses a distributed system. This observation leads naturally to the question of how concentrated vs. distributed systems might respond differently to natural selection. It similarly leads to questions about how information retrieval is achieved in a distributed system in a way that allows entities to respond adaptively to their environment. I don't feel these same kinds of questions emerge as naturally when using analogical reasoning to expand a genetic framework.