Stuttering: An Evolutionary Hypothesis – Genetics; Species; Hierarchy; Social Role; Individual; Specialization; Self-Suppression

Written by Matthew O’Malley


In a NutshellEvolution often selects for the benefit of the species as a whole; not for individual fitness.  The human species requires specialized roles.  Individuals must fill these roles for the species to function as a whole.  There is hierarchy within the human social system which requires the vast majority of individuals to be in non-leadership roles.  In order for the human species to attain the required ratio of non-leadership roles to leadership roles, mechanisms must be in place to accomplish this.  There are both environmental methods to attain this ratio as well as genetic ones.  Genetic inheritance of certain traits increases the likelihood that this ideal ratio is met.  The existence of a genetic predisposition to stuttering may be explained by the species wide payoff this trait has in aiding to meet this ratio.

Evolutionary Selection For The Species; Not The Individual

Most evolutionary vantage points I have encountered view the individual organism as the entity that the process of evolution is shaping to survive.  Selecting the individuals that are “fittest” is often the view that is espoused.  While there is credibility to this perspective, I have been taking more of a macro view on evolution of late.  In this macro view, the individual is viewed as a cog in the species as a whole; as a part or “role” which serves the larger whole that is the species.  From this vantage point, the species is the larger “organism”/entity evolution is shaping to survive (not the solo individual).  This macro lens has been illuminating regarding human nature and likely has implications for stuttering.

To reword, evolution is not only selecting for the benefit of the individual’s survival, but it is shaping the species as a whole for survival, often to the detriment of the individual.

To demonstrate the notion that the nature of an individual organism has evolved and is designed to serve the species as a whole, we need look no further than the honey bee as definitive proof.  The honey bee has evolved the barbed stinger which can stay stuck in the organism it stings.  The removal of the bee’s stinger (due to it staying stuck) profoundly wounds the bee that did the stinging, resulting in its death.  This is the ultimate evolutionary price for an individual organism; death.  Evolution in this real-life example has selected to kill individual bees to better serve the bee species as a whole through the evolutionary selection of the barbed stinger.  This is a clear cut example of how an organism’s individual nature can be of tremendous detriment to itself, but serve the species as a whole.

The human being has many characteristics which are similar to “barbed stingers” in that they hinder the individual’s thriving for the betterment of the species.  We will dive into this later which will aim to further illuminate the nature of stuttering.

There are plenty of examples of this in nature if you look deeply enough.  This honey bee example is likely the most clear cut one.  However, it demonstrates an important evolutionary principle for this piece.  This principle is that evolution selects often for the benefit of the species and not the individual.  This implies that our individual nature is not shaped solely to benefit ourselves or our own survival.  Much of our nature is to our individual detriment, however serves the larger whole that is the species.  Within our nature are profound mechanisms that can work against our own thriving and success in the name of the evolutionary success of the species.  As you’ll see in this piece, I assert that stuttering may be one of them.

Leaders/Followers, Hierarchy, Social Order, Social Role, & Utility

Social status, specialized roles, and hierarchy are fundamental components to the functioning of the human species as a whole.  Each individual must play their role in order for the species, culture, society, or group to function effectively.  In creating these social systems which the human species relies on, there is hierarchy.  There must be leaders and followers.  Examples of organizations that enforce this type of structure with powerful effect are often militaries.  If a person ranks higher than another, there is no questioning who makes decisions.  The person who ranks higher has final say and the person who is of lower rank abides.  Disobedience from the lower rank comes with consequences.  Many cultures have even had caste systems which forced individuals to stay in a certain position of the social hierarchy based on the class they were born into.  Human tribal communities also have hierarchy and specialization.  The need for this organization and social status is ingrained in the human species as it is profoundly important to the survival of the species as a whole.

Humans are not the only species that have hierarchical structures.  If a species is social, it is paired with hierarchy.  Wolves are deeply social.  Within wolf packs there is an alpha who keeps the rest of the pack in alignment and also is the only wolf allowed to mate.  Bees are profoundly social and organizational.  There is one queen who is at the peak of the hierarchy and keeps the hive in alignment with its goals.  There are thousands of worker bees that each specialize to fulfill duties needed for the hive.  There are also hundreds of drones who will be selected from for mating with the queen.

The above are just a couple of examples of how social species organize and fill roles to serve the greater good of the species.  One important commonality to note for this piece is that the number of “leaders” in each species far outweighs the number of “worker bees” or “followers”.

Self-Suppression For The Good Of The Species

Within these social structures, not everyone can be a leader.  As a matter of fact, the vast majority of people have to be “worker bees”, doing the grunt work in order for the species to thrive.  As a result of this, there have to be mechanisms in place to establish this proportion of leaders and worker bees.  Some of the mechanisms that accomplish this are environmental such as caste systems.  However, there are likely genetic mechanisms at play as well.

For the sake of this piece, a leader is an individual who has the ability to assert the self.  Asserting the self in this piece means being able to steer the social group in the direction you see fit.  Leaders are able to assert the self and establish themselves in such a position through various tactics that require certain abilities.  As stated, for the proper functioning of the species only a few can occupy this role.  You need far more individuals serving in “worker bee” roles for the proper functioning of the species as a whole.

Some genetic mechanisms that may be at play in creating more “worker bees” may be things like subservient dispositions and socially shy temperaments which can be influenced by genetics.  These are just a few possible examples.

As is fairly well established also is the genetic predisposition to stuttering.  This genetic predisposition may have persisted evolutionarily for its value to the species in creating self-suppressed individuals to occupy roles outside of leadership.  It can be deeply painful for the individual to deal with a life of self-suppression.  However, evolution has selected for it in serving the species as a whole.  Individuals unable to assert themselves due to inhibited oral communication has value to the species as the species needs the vast majority of individuals to be self-suppressed.  This can serve to explain the genetic nature of stuttering.

Stuttering & Social Role

It is important to note that stuttering has significant interplay with social status.  People who stutter often stutter far more with figures of leadership and far less with persons of low status or no status at all (pets).  This may be an element of the condition which is in place to keep individuals in subservient species roles.

Evolution Selects For Percentages of Traits

It is no secret in the field of stuttering research that there is evidence pointing to a genetic predisposition to stuttering.  The vantage point being offered up in this piece may provide some evolutionary rationale for some species’ benefit for the condition of stuttering in some individuals.  Incidence and prevalence studies on stuttering reveal somewhat stable percentages all over the world in different cultures.  It is generally thought that stuttering incidence (chance stuttering will occur at some point in a person’s life) is about 5%, though more recent research suggests this could be higher (even as high as 9-10%).  Prevalence (percentage of people who stutter at a given moment in time) is about 1%; though more recent data points to a figure a bit lower than this (approximately .75%).  With some of this in mind, it is possible stuttering offers a species wide benefit.  As stated above however, the individual who stutters has acquired stuttering often to their individual detriment but in service to the species as a whole.

This relatively stable percentage across cultures is interesting to note as certain traits within a species often exist at relatively constant levels.  For example, there is a new trait that is getting a significant amount of attention which is the “highly sensitive” trait.  One defining characteristic of this trait is high levels of attunement to environmental subtlety.  It has been estimated that 15-20% of the population has this trait.  Due to this high sensitivity, people with this trait are attuned to more in the environment and often react more powerfully to it as well.  One might describe some people with this trait as “fidgety” or “jumpy”.

While from some vantage points this trait is not the species ideal, it has its benefits in a group context.  For example, let’s say you are a member of a herd of deer that is grazing.  As deer are prey to many predators, they are often on alert for sounds and other stimuli from their environment to detect predators.  All it takes is one deer in the herd to pick up on something in the environment to ruin the hunting opportunity of whichever predator may be lurking.  If one deer picks up on the environmental cues that a predator is lurking, all of the deer know about it due to this one deer’s alertness.  In scenarios like this, it is helpful to have one deer in the herd that is “highly sensitive” to this stimuli which can save the lives of other deer.

Social species evolve to keep traits like “high sensitivity” at a certain percentage to serve the greater goals of the species.  So, even though this trait can have negative impacts on the individual and is not considered the “fittest” trait, it is serving a function within the species at large.  Herd of deer that have individual deer with this trait are more likely to survive.  Therefore, herds that have these genes continue to pass on.

This information is interesting in that stuttering persists across cultures at a fairly stable rate of approximately 1%.  This stuttering selection may have species wide payoff in creating “worker bees”.

In recent research on the employment of people who stutter, this trait continues to do its job as people who stutter earn more than $7,000 less annually than their fluent counterparts according to this study.

Suppression of Self is a Survival Need

Gabor Mate, an MD and thought leader on trauma and the social nature of the human species is a brilliant mind.  In capturing a view of his that caused me to reflect quite a bit, he believes that being in touch with the authentic self and manifesting it are survival needs.  In other words, asserting one’s self, expressing one’s inner condition, and manifesting one’s self in others is a survival need.  While there is truth to this and there is a deep individual desire to meet this need in life, the species wide survival need is the opposite; self suppression.

The amount of selves in society allows for an extremely limited amount of self-expression as often only one route and one voice can manifest and be chosen.  Self-suppression is instrumental and indispensable to social order and hierarchy.  This need within our species for self suppression can help explain many of the versions of human suffering that exist today.

The profound species wide need for self-suppression is evidenced in what we term the “socialization” of children.  Socialization is an environmental mechanism to enforce and create species norms that individual “cogs” within the species must abide by for the species to function effectively.

I’m not arguing against any of this or taking a moral stance on any of it.  I’m simply reporting a compelling vantage point I have been observing from.

On A Spiritual Note

I understand that people can be “leaders” in different ways and there may be much more to life than these species’ roles.  Status is largely a human concept and does not speak to the inherent worth of the soul.  I state this as some may take offense to some of the positions articulated in this piece, however, my personal view on a deeper level than evolution is that each human being is spiritual and their worth and/or status is not tied to their worldly role.

Asides & Other Points

Mating and mate selection may have something to do with the approximate 4:1 male to female ratio in stuttering.

There are many examples of people who stutter who have served in leadership roles.  Stuttering does not completely mandate a status, however, it increases the chances for a “worker bee” type role.

The peer socialization process may also contribute to filling more non-leadership roles.  Bullying and the “meanness” of kids may be an environmental social species mechanism for creating low self-image in many individuals in order to create non-leaders.

Relational trauma and psychological damage is so common-place in the human species that I am beginning to think it serves a purpose.  This purpose may be to create non-leadership.

In creating individuals who are not in leadership positions but are striving very diligently to climb the hierarchical ladder, you create hard working and motivated individuals at all rungs of the species.  This dis-contentedness can serve to spur people to “work hard” which contributes to the species functionality.

A person who stutters who also has profound leadership traits and dispositions in other areas of their make up may struggle the most.  Individuals with more subservient dispositions and nonchalant make-ups likely cope better.

Persistence of stuttering does not indicate that changes in a person’s speaking behaviors are not possible.

Stuttering may be one mechanism to increase “worker bee” roles in order to serve the species.  There will be some individuals who have leadership traits and mindsets in all other areas.  This can lead to intense frustration.

There are far more traits and parts of our nature that can be explained by the selection of traits for the betterment of the species but to the detriment of the individual.  Some of our most core desires serve the species’ survival and not the individual.  For example, sex is not needed for the individual’s survival.. However, it is a profound need for the survival of the species.  As a result each individual carries this need for sex to serve the species.

It is also important to note that a genetic predisposition to stuttering does not necessarily mean a person will stutter.  In identical twin studies, if one twin stutters, approximately 65% of the time the other twin stutters.  With genetics there is flexibility in regards to the phenotype which expresses itself based on environmental factors.  Stuttering could be activated in certain environmental conditions to fill certain social roles.

7 thoughts on “Stuttering: An Evolutionary Hypothesis – Genetics; Species; Hierarchy; Social Role; Individual; Specialization; Self-Suppression

  1. A great piece. Lots of important ideas here that deserve to be followed up.
    Its worth noting that Sheehan wrote a lot about the relationship between social hierarchy and stuttering… and even came up with a theory, which he called “role conflict theory of stuttering” which broadly supports what you have written (note that this is not the same as his “approach avoidance conflict theory”, for which he is much better known).
    I’m also conscious that Stevens and Price’s “Group-Splitting Hypothesis” (an evolutionary theory of schizophrenia) could equally well be applied to stuttering. In their book “Evolutionary Psychiatry” Stevens and Price also propose a wider evolutionary theory that suggests that a wide variety of behavioural conditions or “disorders” (potentially including stuttering) can be neatly explained from an evolutionary perspective. They suggest from an evolutionary perspective, mental conditions seem to fall along two axes… disorders of hierarchy and disorders of spacing ( google “spacing disorders” for an explanation). I think stuttering could potentially be associated with both axes, not just hierarchy.

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    1. Thanks Paul for the informative input. I am fond of some of Sheehan’s ideologies and have read some of his views regarding role and stuttering. It intrigued me, however, I could not locate any piece written first hand by him explaining it in detail, The best quotes or explanations I have found are ones such as what follows, which is on the Sisskin Stuttering Center’s page:

      Begin quote…
      “People who stutter experience periods of fluency: “Sometimes I stutter, and sometimes I don’t”. The allure of fluency leads those who stutter to hide one’s identity as a person who stutters. “Playing the role” of someone who is fluent requires false role behavior, for example, pretending to think, speaking in odd ways, pretending to not know an answer to a question. When stuttering is revealed, role conflict ensues, resulting in shame, that is, negative feelings about “self”. Role congruency, on the other hand, requires self-acceptance as a person who stutters.”
      End quote…

      There it seems the role ideology is primarily about accepting one’s self as a person who stutters vs. attempting to be a “false self” that is a non-stutterer.

      I have wanted to read Sheehan more in depth. If there is something accessible written first hand by him, please point me to it. I am a fan of a good portion of Sheehan’s work and would enjoy the information. I’m currently reading the second edition of Yairi & Seery’s text, cover to cover so maybe I will come across a more thorough piece in there.

      I looked up group slitting hypothesis and as well as spacing disorders. Interesting. Evolutionary theory is often a goldmine in terms of providing explanations so I’m interested in Stevens & Price’s book.

      Keep up the good work and don’t be a stranger.


      1. I was thinking of Sheehan’s 1970 book: Stuttering: Research and Therapy. I read it quite a few years ago, and have just re-found it in my bookshelves. Chapter 1 discusses his Role conflict theory. Here are a few quotes…
        “Stuttering behaviour changes with role change… .the occurrence of stuttering is in part a function of the relationship between the stutterer and his listener. Some stutterers experience no fear when they play a dominant role. One may give a fluent public address but stutter to individuals in the audience before and afterwards. A child may block severely before one parent but speak easily to the other. An army enlisted man could never say “sergeant” until he became one but he still stuttered on “lieutenant” on “sir,” and on the titles of all the higher ranks. The fact that many stutterers can act in plays seems to show the effect of changed role.” (page 9)

        “You stutter to the role, not to the person temporarily occupying the role. And roles are attached to positions, to statuses, not to the person momentarily enacting the role. Stuttering varies both with the role of the speaker and with the role of the listener. Perhasp stuttering is a role disorder primarily, and an interpersonal relations disorder only secondarily. Difficulty with certain classes of persons branches out from the positions they occupy and the roles they perform, not necessarily from their individual personal characteristics.” (page 10)

        “As behavior, stuttering is predictable to a high degree from the relative status of speaker and listener. When the perceived status of the speaker is low relative to that of the audience, stuttering tends to be severe. When the stutterer speaks to a peer figure, as to another stutter or close friend, stuttering tends to be moderate. And when the stutterer feels high in self-esteem, as by the intoxicating effects of love, or of alcohol, or of observable success, and feels no awe of the listener, he speaks with comparative fluency. ” (page 13)

        Anyway, in that chapter, he gives lots of examples of how stuttering tends to be associated with perceiving one’s self as having a low status, and how it changes as one’s perceived status changes. Reflecting what you have written in your response, he then goes on to talk about how stutterers tend to get into playing “false” roles, pretending they don’t stutter etc.

        Liked by 1 person

      1. My interpretation of Sheehan’s perspective is that the problem of trying to hide one’s stuttering and the tendency to try to portray oneself as a non-stutterer is tied in with a tendency to consider low societal status to be “bad” (and a source of shame) and high status to be “good” (and a source of pride). This is where your writings about the need (from an evolutionary perspective) for a variety of statuses in a population is useful. If one can understand and accept that societies need a combination of both low status and high status people in order to thrive, and that low statuses are equally important and valid, and in no way reflect on one’s value as a human ( spiritual) being, then the motivation to try to hide one’s stutter and to adopt a false role disappears. … and paradoxically one’s status is likely to rise as a result.

        Liked by 1 person

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