Runaway brain‐culture coevolution

How Alexander Markov's model helps to solve the mysteries of our evolution: the brain grows, memes spread, and our ancestors, it seems, knew how not only to hunt, but also to "troll"!

Today we will talk about a model that has taken on the mystery of the sharp acceleration of human brain growth, using agent-based simulation. Let me remind you that this means studying the properties of a complex system by setting environmental parameters and behavioral patterns for each individual populated in it. Scientist Alexander Markov created a model that was intended to help describe the processes that humanity went through directly in its cradle[1].

The TribeSim model, developed at the request of a scientist by his son, is an agent-based simulation designed to study the evolution of genetic and cultural factors in a social environment. The main principles and elements of the model:

1) The population consists of social groups that compete for limited resources.

2) The maximum size of a group is determined by the parameter G, after which the group splits into two.

The environment provides a fixed amount of resources R per year. Resources are distributed between groups depending on their "hunting efficiency" (HE).

Within the group, resources are distributed based on "Machiavellian efficiency" (TrE), which creates competition between group members. A successful individual must maintain a balance between personal and intergroup egoism. That is, to be so social and able to negotiate that he can successfully function in group hunting and potential conflicts with neighboring tribes, but at the same time be smart enough to get more resources when distributing them in the group.

Each individual is born with genetically determined initial values of HE and TrE. Brain capacity and memory (MC) determine the capacity for social learning and storage of "memes" - units of cultural information. Brain capacity increases the costs of maintaining life and reproduction, which creates evolutionary trade-offs.

Let me remind the reader that a meme (check me out on Wikipedia) is any cultural idea, symbol, manner, situation, or behavior that is consciously or unconsciously transmitted from person to person through speech, writing, video, rituals, gestures, etc. The term was first coined by Richard Dawkins in 1976 in his book The Selfish Gene. In this article and most of the following articles in this series, we will use the word meme to mean a unit of cultural information. In the model under discussion, memes can be useful (HE or TrE), useless, or even harmful. Memes are created, transmitted through social learning, and forgotten with a certain probability.

The complexity of memes is limited by the memory of an individual. The simulation cycle was one year, during which the population acquired resources, distributed them, invented memes, lost and acquired new members.

Key Takeaways

1. Cultural drive as a driver of brain evolution.

The mutual development of culture, social skills, and cognitive abilities leads to positive feedback, accelerating the growth of brain volume. Effective social learning facilitates the accumulation and transmission of complex cultural skills, which creates selection pressure for improved cognitive abilities.

2. Intergroup competition strengthens cooperative cultures.

Competition between groups facilitates the spread of cultural traditions that are beneficial to the group, such as hunting skills. This reduces the spread of "parasitic" memes, but can also limit brain growth, since it increases the pressure to adapt at the expense of limited resources.

3. Long lifespan drives culture.

Longer lifespan increases the accumulation and transmission of knowledge between generations, promoting a more complex culture. It also strengthens cultural drive, since older group members play a key role in maintaining and spreading memes.

4. Vicious cycle of meme simplification" limits brain evolution:

As brain size and memory increase, cultural memes become simpler to spread more easily. This reduces the selective pressure for further brain growth, which could lead to stagnation or even a decrease in brain size in the long term.

5. Complex culture is the most powerful driver:

A combination of individually beneficial (Machiavellian) and group (cooperative) memes enables faster and more sustainable cultural and brain evolution. Such a culture adapts to varying levels of intergroup competition and migration, supporting evolution even in changing conditions.

The model identifies genotypic and phenotypic variables that model the evolution of cognitive and cultural characteristics. These variables are important for understanding the interaction of genetic and cultural factors in the model. Genotypic variables are heritable traits that are determined by genes and can change through mutations. The main genotypic variables in the model are: memory capacity, learning efficiency (the probability of successful social learning, teaching efficiency (the probability of successful teaching of other individuals). These parameters are determined genetically, are passed on to offspring and can evolve under selection pressure.

Phenotypic variables are manifestations of genotypic characteristics in the behavior or cognitive abilities of individuals. The phenotypic value of a variable is defined as the sum of the genotypic value and the effects of the memes that the individual has learned. For example, the phenotypic value of learning efficiency = the genetic value of learning efficiency + the influence of memes associated with learning.

The article presents graphs comparing genotypic and phenotypic values ​​of variables such as LE (learning) and TE (teaching). Memory load data (which memes take up more space) is also presented. In the figure we can see genotypic/phenotypic gap: phenotypic values (including meme effects) are higher than genotypic values. This indicates the importance of cultural evolution in addition to genetic evolution. For example: high values for teaching effectiveness indicate that teaching was improved by cultural transmission of the relevant memes. And we see the teaching meme success; teaching-related memes take up a significant portion of memory. This shows their "viral" nature: they spread efficiently, helping their bearer to transmit knowledge. God bless teachers!

Also figure shows the dominance of certain categories of memes: cooperation-related memes (HE) dominate when intergroup competition is high, as they ensure the survival of the group. Teaching efficiency memes occupy more memory than learning efficiency memes, reflecting their high contribution to evolutionary advantage.

What do I like about this model? First, it is one of the best approximations to understanding human history, in this case its very beginning, from the point of view of predictive science. It cannot help but be fascinating. Second, the model really seems well thought out and demonstrates the desired positive feedback that should have led to an unprecedented acceleration of brain growth in our ancestors. Special thanks to the authors for the fact that the model is gender neutral and does not assume, like some others, that the brain was needed only by men, and women were somehow for company.

What criticism is possible? The model contains a huge number of independent variables, which, of course, leaves some questions and implies, at the very least, further research. Secondly, there is still no answer to the question of why, of all the species, only humans got into this brain growth carousel? What was the initial trigger? We still have a lot to learn.

[1]   Markov, A. V., & Markov, M. A. (2020). Runaway brain‐culture coevolution as a reason for larger brains: Exploring the “cultural drive” hypothesis by computer modeling. Ecology and evolution, 10(12), 6059-6077.