(This article originally appeared on Mario’s blog at

I’m fortunate enough to have a lot of friends, but not nearly as many as my Facebook profile would suggest. In fact, as I write this—at least according to Facebook—I have 1,769 “friends.” But scrolling through the list of those 1,769 people (well, part of it, at least), I quickly realize that I have no clue who many of these people are. As I look at most of them I don’t recall if they sent me invitations or I sent them invitations, and I couldn’t tell you anything about them beyond what I can read on their Facebook bio.

I am certain that I am not alone in this. Despite our best intentions, we simply cannot keep track of that many people.

In fact, according to Robin Dunbar, we can really only keep track of about 150 people, so most of my Facebook friends are not friends at all—they are merely people I sometimes encounter in cyberspace.

Robin Dunbar is an anthropologist and evolutionary biologist who had a profound insight into the way groups work. After observing many different species of primates, he started to notice a correlation between brain size and the size of the social group in different species—it seemed that the larger the brain, the larger the social group tended to be.

Extrapolating from human brain size compared to other primates, he suggested that the number of people most humans can keep track of—knowing who they are and how they relate to each other—is about 150. (This is commonly referred to as “Dunbar’s Number.”) Of course, that number varies from individual to individual, but in general most of us can keep track of about 150 people who, according to Dunbar, “we would be comfortable bumping into in a bar and having a spontaneous and comfortable conversation.”

Up to about 150, groups can be less rigid in their hierarchy and more fluid in their interactions. When the number of the group grows beyond that we need to start developing stricter rules and procedures to govern interactions. This explains why a small start-up can be agile, decentralized, and fluid while a conglomerate cannot. When even the most agile company gets beyond a certain size it needs to bring in seasoned management to put order on the chaos that starts to occur when the business hits Dunbar’s Number. This pattern has been repeated over and over again throughout human history and continues today. It is hardwired into us because for eons our ancestors only had to deal with small groups and we have been living in larger groups for a very short time, evolutionarily speaking. A primitive tribe of 150 or fewer people could get along without a constitution; a country of tens or hundreds of millions cannot. Today, thanks to the internet and air travel we live in a global community. It is no wonder that people are reacting against globalism—our embedded evolutionary wiring just can’t handle the change.

Dunbar’s Number and our current state points to the tension that often occurs between cultural evolution and our biological evolution. Cultural evolution works much faster than biological evolution, so even though we consider ourselves rational creatures who follow the stated laws and social guidelines that govern society, our brains often chafe at our ever-evolving cultural mores because they are hindered by our limited ability to think beyond our 150-person “tribe.”

The Navigating instinctual domain (referred to by others as the “social instinct”) is a cluster of evolutionary adaptations that, at their core, help us manage Dunbar’s Number. It is a focus on how we orient to the group, understand implicit and explicit mores, and find our place in the pecking order. These adaptations equip us with tools for how to act as part of a group. (See for a brief overview of the three instinctual domains.)

This domain includes many adaptations, though for ease of understanding I separate them into three subdomains: trust and reciprocitystatus and identity, and power and influence dynamics. In this article, I will address the first subdomain, trust and reciprocity.

Humans are a social species, meaning that we live in groups and depend on other members of the group for our wellbeing (and they depend on us for theirs). Key to living in a group is ensuring that we know who we can trust and convincing others that we are trustworthy as well. Trust allows for reciprocity—the cooperation and exchange of favors upon which we are so dependent. Trust sends the message that I’ll scratch your back if you scratch mine. Group members who can’t be trusted are a threat to our wellbeing, and were a threat to our survival in our evolutionary past when we were even more interdependent than we are today. We have inherited evolutionary adaptations that make us highly sensitive to issues of trust and reciprocity because this sensitivity increased great-great-great-…-grandpa’s chances of surviving and reproducing. So, even today in our more enlightened age, if I share my food with you and you do not reciprocate, some part of my brain tells me that you have become a liability. In order to protect myself and those I care about (i.e., other members of the tribe) from you, I will be sure to tell them that you are untrustworthy. If I have not yet established whether or not I can trust you based on my own interactions, I will ask others in the group about their experiences with you and whether you have proved to be trustworthy in your interactions them.

The gathering and exchange of information (including what we often call “gossip”) is part of the glue that holds the tribe together, and it is the life blood of the Navigating domain. It not only lets me know who I can trust and who I can’t, it serves the social function of keeping freeloaders in check—if I misbehave and violate trust, my misbehavior will be communicated to the group and no one will trust me enough to attempt to cooperate or exchange with me. This leads to ostracism, and our ancestors could not survive long if they were kicked out of the group. Even today, the mechanisms that helped those ancestors survive and reproduce by maintaining a place in the tribe run deep in our psyche.

(I have seen others refer to this exchange of information in the Navigating domain as “Transmitting,” which I think is an error. Transmitting describes the passing on of information but not the receiving of information; it is one-way rather than reciprocal. The reason I refer to the so-called “sexual” domain as “Transmitting” is because that domain is all about this one-way passing of information. Those in Transmitting mode tend to exchange with others only to the point where it gives them an opportunity to transmit to a receiver; they probe and listen to find the frequency the other is receiving on and then they begin transmitting. I think those who use the word “transmitting” related to the Navigating domain would be better served to use “exchanging” regarding this activity to capture the two-way nature so fundamental to the domain.)

There are more behaviors related to this subdomain than gossip, or course, and not all of them are as specific an activity of gossip or exchanging information. Such exchange is only one of the more easily identifiable behaviors that support our ability to track trust and reciprocity. Navigators are not simply spreaders of information, they are collectors of information about people and the ways they interact, squirreling away nuggets that could prove useful someday. They are students of politics in the broadest sense, seeking to understand the relationships and mores that shape the group so they can use that information to their advantage or at least not run afoul of the expectations of others. They query and listen, often being quite skillful at building rapport and getting others to open up.

Some Enneagram teachers take a very negative view of the instinctual biases and I have been criticized for suggesting that people with a dominant Navigating bias tend to be effective at Navigating, a criticism that makes absolutely no sense to me. As with the nine Ennea-type strategies, it seems to me that people are “good” at them when they express them adaptively and “bad” at them when they express them maladaptively. I have found that, as with the other instinctual domains, Navigators who are psychologically healthy and generally effective in life are usually very effective in adaptively applying these skills, while people who are generally dysfunctional tend to be ineffective Navigators even though they tend to obsess over issues related to this domain.

I have found that the trust-and-reciprocity subdomain, with its emphasis on subtle group dynamics and need to tune into the seemingly superficial chatter that occurs in groups, is the area of the Navigating domain in which those with a dominant Preserving bias and those with a dominant Transmitting bias seem to struggle the most.

Broadly speaking, Preservers tend to err on the side of not trusting enough (particularly when it comes to issues related to resources and safety) and Transmitters tend to err on the side of trusting too much (particularly when it comes to assuming the good intention of others in general). Preservers tend to be somewhat skillful at tracking group dynamics, but get frustrated with it far more quickly than Navigators do and tend to want to get back to focusing on more practical matters rather than sit around and chit-chat. Transmitters are often good at reading people’s initial reactions to them and finding a way to connect, but they tire quickly of small talk, have little interest in gossip, and often miss the subtle signals and currents in a group that the Navigators tend to read very well. In working with clients over two decades, I have found that this indifference to and inability to read and react to subtly shifting political currents is one of the most likely derailers of the careers of Transmitters.

For better or worse, our large- and small-scale group dynamics and politics are governed by the adaptations in this instinctual domain, and all of us would do well to become more skillful at the behaviors we can’t avoid if we want to be an effective part of the group.



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