It is impossible to discuss immune systems of any sort without also discussing organisms. Immune systems are inherent parts of organisms, designed to protect against external invaders, such as infectious diseases, and internal rogue elements, such as cancers.

With mental immune systems, it might seem that the organism is an individual person and the immune system is a set of cognitive adaptations designed to protect against harmful beliefs. In this essay, I will argue that the concept of 'organism' must be expanded to include groups as organisms. When we do this, the concepts of both “mental” and “immunity” can be seen in a new light.

The concept of society as an organism stretches back to antiquity and the tradition of group-level functionalism, represented by figures such as Emile Durkheim, was dominant in the social sciences until the middle of the twentieth century. Then it was eclipsed by more reductionistic and individualistic perspectives.  According to the social psychologist Donald Campbell,1 writing in the 1990s, “Methodological individualism dominates our neighboring field of economics, much of sociology, and all of psychology’s excursions into organizational theory. This is the dogma that all human social group processes are to be explained by laws of individual behavior—that groups and social organizations have no ontological reality—that where used, references to organizations, etc., are but convenient summaries of individual behavior.”

This giant mood swing also took place in my home discipline of evolutionary biology. Before the 1960s, it was common to suppose that behaviors evolve “for the good of the group” and that supra-individual entities, such as single-species societies and multi-species ecosystems, were functionally organized. Starting with the publication of G.C. Williams’ Adaptation in Natural Selection in 1966, this view became branded as deeply mistaken. The individual was the one and only unit of selection. In his 1976 book The Selfish Gene, Richard Dawkins took reductionism a step further by describing the gene as the one and only unit of selection.

Thankfully, this tide of individualism and reductionism started to recede in the closing decades of the twentieth century. I am proud to have played a role in its subsidence.2 Two key concepts for the purposes of this essay are multilevel selection (MLS) and major evolutionary transitions (MET). According to MLS, natural selection can operate at multiple levels of a multi-tier hierarchy, such as from genes to ecosystems in biological systems and from individuals to global society in human social systems. Functional organization can evolve—or fail to evolve—at any level, depending upon the relative strengths of the different levels of selection. According to MET, these relative strengths are not static but can themselves evolve. When mechanisms evolve that suppress lower-level selection to a sufficient degree, then the higher-level unit becomes so functionally organized that we call it an organism.

The idea that organisms can evolve, not only by small mutational steps from other organisms but also by social groups evolving to become sufficiently cooperative, was beyond Darwin’s imagination. Today, every entity that biologists call an organism is regarded as a MET, including:

  • The origin of life as groups of cooperating molecular reactions.
  • Nucleated cells as symbiotic communities of bacterial cells.
  • Multicellular organisms as societies of single cells.
  • Eusocial species—including but not restricted to the familiar ants, bees, wasps, and termites—which qualify as “superorganisms” by virtue of their high degree of cooperation, even though their members might be dispersed over an area of several square kilometers.
  • The genetic evolution of our species, resulting in hunter-gatherer groups and small tribes that were vastly more cooperative than most other primate species. This includes the capacity for symbolic thought as a separate stream of inheritance, which first evolved by genetic evolution and has been co-evolving with it ever since.
  • An expansion in the scale of cooperative human societies over the past 10,000 years, with many collapses and reversals along the way.

To summarize, the concept of society as an organism is back and now stands on a far stronger theoretical foundation than in the past. This requires adjustments in how we think about our two key words, “mental” and “immunity”.

From a multilevel perspective, the word “mental” cannot be restricted to individual cognition. If groups can be organisms, then they can have group minds. This has become conventional thinking for the study of social insects. In some respects, an ant or honeybee acts as a self-contained cognitive unit in its own right, but in other respects, it acts more like a neuron in a neural network. When we examine the major categories of human cognition, such as perception, memory, and decision-making, we can see that all of them are deeply social.3 Our capacity for symbolic thought is so communal that it is nearly impossible to think of an individual person as detached from it. The evolutionary neuroscientist Terrence Deacon has provocatively called humans “symbolically eusocial”, meaning that the glue holding groups together is not genetic kinship, as with the eusocial insects, but our symbolic belief systems. This is indeed a return to the group-level functionalist view of Durkheim, although this time on a much stronger scientific foundation. Durkheim wrote: “In all its aspects and at every moment in history, [human] social life is only possible thanks to a vast symbolism”.

To summarize, the concept of a human group mind might sound like science fiction against the background of individualism, but it is richly justified from a multilevel evolutionary perspective.

The same goes for immune systems. Any entity that qualifies as an organism must have a subsystem that defends against external invading agents and internal rogue elements—the analogs of infectious diseases and cancers for the vertebrate immune system.

Human moral systems make great sense from this perspective.4 The moral system of a group typically defines a boundary between “us” and “them” and regulates behaviors within the group. Deviant behaviors are defined as cheating—a form of cancer—and punished. Foreign beliefs are tagged and removed, like infectious diseases. One might argue that the new-fangled interpretation doesn’t add much value to more conventional views of morality, but it’s hard to deny that it fits the functional description of a group-level immune system.

Complications arise when we consider matters of the utmost importance in modern life, such as the need for a global moral system and the need to distinguish scientifically validated knowledge from “fake news”. These are essential goals for the future, but it’s a mistake to read them into the group-level immune systems of the past or—for the most part—the present.

Throughout history, moral systems have almost always been less than universal, applying only to an “us” and excluding a “them”. Relations with them were not always adversarial, but they still operated according to a different set of rules. The scale of social interactions was too limited to even imagine the whole earth as something that might become a single cooperative society. The Bah’ai faith, which originated in Persia (now Iran) in the mid-1800s, was arguably the first to extend itself to all nations and creeds. The first war to be called a World War took place in the early twentieth century, followed by the first attempt to create a worldwide governing body—the League of Nations. From an evolutionary perspective, the us-them distinction has always been a feature, not a bug. We need to keep this firmly in mind when we analyze the moral systems of the past and present and work toward achieving a moral system for the whole earth in the future.

Likewise, it is an oversimplification to suppose that group-level immune systems are designed to distinguish fact from fiction. Instead, they are designed to distinguish all beliefs and practices with fitness value (the survival and reproduction of the group) from all beliefs and practices that pose a threat to fitness. This means that adaptive fictions are embraced and defended, while maladaptive facts (“inconvenient truths”) are vigorously attacked. QAnon has an immune system, no less than opponents of QAnon.

As with the basic fact of group-level immune systems, which becomes evident after the concept of group-level organisms is re-established, evidence for adaptive fictions and maladaptive facts is all around us, once we know what to look for. Adaptive fictions are by no means confined to religions. One of my favorite books on this subject is titled The Invention of Tradition, by the historians Eric Hobsbawm and Terence Ranger. How a culture imagines its past is at least as consequential for action as how it imagines its gods. Hence, every culture invents and attributes greater antiquity to its traditions than is actually true, as any competent historian can reveal.

Another book that springs to my mind is My Fundamentalist Education: A Memoir of Divine Girlhood, by Christine Rosen. Rosen outgrew her fundamentalist upbringing but looks back upon it without rancor, which makes her a good ethnographer. What she describes is a culture that had to work ceaselessly to preserve its central beliefs and keep out the beliefs of modern secular society. The group-level immune system was working overtime—including the rejection of Darwin’s theory of evolution.

Here’s another example from modern life: the phenomenon of whistleblowing. A whistleblower is a member of a group that has become cancerous with respect to a larger group. Two moral systems are therefore in play. Whistleblowers are conforming to the moral dictates of the larger group, often by asserting facts that are being denied by the smaller group. This triggers the immune system of the smaller group. Few people are hated more than whistleblowers, within the group that is being exposed. They are treated within their cancerous groups as if they were the cancer.

My last modern example, for the purposes of this essay, is Wikipedia. The heart and soul of Wikipedia (to use the language of superorganisms, which springs so easily to our lips!) is to create a repository of factual information. In this case, separating fact from fiction is the purpose of its immune system—but only because it is the raison d’etre of the organization.

The vertebrate immune system is a symphony of cooperation among its specialized cell types. So is Wikipedia’s immune system, as I discuss at length in a video conversation with one of its senior volunteers, Anne Clin (aka Risker). Just as multicellular organisms are bombarded at every moment with potentially harmful disease agents, Wikipedia is bombarded by individuals and organizations eager to add content that serves their interests, which more often than not involves departing from the facts of the matter. The metaphor of being a superorganism in need of an immune system is sufficiently compelling that Wikipedians talk about it that way to themselves, largely unaware of the developments in evolutionary science that make the concepts more than metaphors.

Make no mistake: Regardless of the past and present, there is an urgent need for a moral system that defines “us” as the whole earth, including the biosphere in addition to humans. This will require a high degree of respect for factual knowledge, while also allowing a spiritual and artistic dimension that captures the heart in addition to the mind. Time will tell whether an explicitly multilevel evolutionary perspective will add value to this enterprise. My prediction is that it will be a game-changer.


For more on this subject, I recommend a series of 24 video conversations titled “The Science of the Noosphere”, which traces the arc of Major Evolutionary Transitions (METs) from the origin of life to the future of the Internet Age. Viewing the series, which includes my video conversations mentioned earlier, is the best preparation I know for becoming current on the multilevel evolutionary perspective.

[1] Campbell, D. T. (1994). How individual and face-to-face-group selection undermine firm selection in organizational evolution. In J. A. C. Baum & J. V. Singh (Eds.), Evolutionary dynamics of organizations (pp. 23–38). Oxford University Press.

[2] My website,, is a complete archive of my work, including a short memoir that recounts the group selection controversy from my personal perspective. My two main academic books on the subject are Unto Others: The Evolution and Psychology of Unselfish Behavior (with Elliott Sober), and Does Altruism Exist: Culture, Genes, and the Welfare of Others. Both can be purchased through my website.  

[3] See my video conversation with James Coan and Garriy Shteynberg titled “Human Groups as Organisms” for more.

[4] Another TVOL special edition explores morality from an evolutionary perspective [link].