The Evolution of Human Agency – Part 1
The evolution of human agency.
In a previous essay series, we explored how recognizing human agency is central to respecting people as responsible citizens who can govern themselves in a democracy. In this series of essays, we’ll explore the evolutionary origins of human agency, the key steps in that development, and the need for society to uphold the types of social arrangements that made the development of human agency possible in the first place.
As Brian Villmoare writes in The Evolution of Everything: The Patterns and Causes of Big History:
Under complexity theory, once a brain reaches a certain size (in terms of numbers of interconnected neurons), consciousness simply emerges. This is a slippery concept to grasp, because we are used to thinking of different organs having specific anatomical functions. Consciousness is not like this – it was never selected for, nor does it have a true biological purpose. Rather, it is an incidental byproduct of selection for increased numbers of neurons in the brain.
Beyond consciousness, humans have a more developed sense of “agency.” What does that mean, and how did that come about? That’s the subject of Michael Tomasello’s book The Evolution of Agency: Behavioral Organization from Lizards to Humans. Tomasello writes:
Primates and other mammals seem to be more “intelligent” than smaller-scale creatures such as insects. But the basis for this impression is not at all clear. It is certainly not based on differences in the complexity of behavior: ants building anthills, spiders weaving spiderwebs, and bees communicating the location of nectar to hive mates are as complex as, or more complex than, anything any primate or mammal can do. The issue is not complexity but control. Even when they are doing something highly complex, the behavior of ants and spiders and bees does not seem to be under the individual’s control. Their evolved biology is in control. In contrast, even when they are doing something relatively simple, primates and mammals seem to be making active and informed decisions that are at least somewhat under the individual’s control. In addition to their evolved biology, they are operating with a psychology of individual agency … Individual agency does not mean total freedom from biology; it is always exercised in the context of an organism’s evolved capacities. As just one example, it is clear that a squirrel is somehow preprogrammed to cache nuts. But the exigencies of a particular landscape at a particular moment are unique in ways for which the organism cannot be biologically prepared in detail, and so the individual squirrel, as agent, must appraise the current situation and make a caching decision for itself. For many organisms, the degrees of freedom in making such decisions are quite limited—and may differ in different behavioral domains—but such degrees of freedom nevertheless often exist, and within them it is the individual agent that decides what to do.
Tomasello asks “How and why did agency evolve, and why more so for some species (in some behavioral domains) than for others? … We need an account that traces the evolutionary steps in agentive behavioral organization from creatures who make few and highly constrained decisions to creatures who quite often decide for themselves what to do. Perhaps surprisingly, it turns out that there are only a few such steps.”
Tomasello makes clear that agency is on a continuum:
The issue is not whether something is innate or learned, but rather the degree to which it is controlled by the individual. Thus an organism may have a genetically wired preference for sugary foods, but from the point of view of agency, the issue is whether this preference compels the organism to consume every sugary food it encounters, or whether this preference is merely one factor among several in the organism’s individual decision of what to eat.
All living things have biological needs, but as Tomasello explains, agency is a trait that allows some living things, but not others, to choose to some extent the means by which those needs can be fulfilled:
A key way that the behavior of a species evolves is by the evolutionary emergence of new goal states that are more or less hardwired by Nature (e.g., an evolved preference for a new food), but with the behavioral means of achieving those goal states left up to the individual to figure out on its own (given its existing cognitive and behavioral capacities) … Behaving as a psychological agent means that the underlying psychological processes that generate actions are organized in a particular way. An agent does not just respond to stimuli but actively directs (or even plans) its actions toward goals, actively attending to relevant situations in order to do so. And an agent does not just “aim and shoot” at its goals ballistically but rather flexibly controls (or even executively self-regulates) its actions by making informed decisions about what will work best at various points in a dynamically unfolding situation. Methodologically, the main evidence for psychological agency is the “behavioral flexibility” of individuals, especially in novel circumstances … Behavioral flexibility suggests that the individual organism is finding new ways in the moment to deal with challenging new circumstances … The evolutionary hypothesis is that when individuals regularly face situations of uncertainty, the individuals that fare best are those that operate agentively to flexibly assess the situation at hand and make a decision informed by the relevant local contingencies … and then monitor and self-regulate behavioral execution as it unfolds … Scientists infer psychological agency when the organism acts flexibly toward its goal even in novel contexts. To behave in this flexible manner, the individual must go beyond a stimulus-driven, one-to-one mapping between perception and action. The individual must be capable of choosing to act or not to act, or among multiple possible actions, according to its continuous perceptual assessment of the situation as it unfolds over time.
The evolutionary evidence isn’t as plain as a fossil on the shelf. But as Tomasello writes:
Our question is how human agency evolved, in terms of the various evolutionary steps leading to it. In principle, we could answer this question by examining the history of agentive organization from humans’ most ancient animal ancestors up to contemporary humans. But, of course, such a history is impossible in the sense that behavior does not fossilize (nor does brain tissue). But behavior does show continuity over time across related species, and this suggests the basic strategy of comparative biology: searching for the roots of human agency in contemporary species that are generally representative of some of humans’ various animal ancestors. From among extant species, we may choose particular model species (or classes of species) on the basis of their hypothesized similarity to ancestor species at key evolutionary junctures … [T]he first organisms with nervous systems were wormlike, the first vertebrates were lizard-like, and the first mammals were squirrel-like. Chimpanzees are as good an ape as any to represent early great apes, and for early humans, we can make some analogies to contemporary human children.
Tomasello starts with worms:
[U]nicellular creatures alive today do not act to pursue and consume nutrition and then stop when sated (indicating goal pursuit and satisfaction); they constantly move and consume more or less as “filter feeders.” Their “decisions” are mechanical, and indeed, they do not even have separate sensory and decision-making mechanisms, only molecules sensitive to nutritious and noxious chemicals, leading automatically to certain actions … Such simple creatures cannot decide not to move toward nutritious chemicals, even when they are already sated, and they cannot make connections between their actions and the results to determine success … Then, more than 500 million years ago, there emerged a wormlike creature that was the first human ancestor to operate with a nervous system: the urbilaterian … All 302 of its neurons—many of which are clustered in ganglia, and 32 of which serve a chemosensory function—have been identified, along with all their synaptic connections. Not only do the chemosensory neurons detect either good or bad things and “signal” the motor neurons to produce bodily contractions that propel the organism either toward or away from those things, but C. elegans also uses the rate at which it is ingesting food, typically bacteria, to detect the location of richer and less rich clumps. Moreover, if a behavior such as forward movement brings a bad result (e.g., a noxious chemical), the creature can perform one of two actions to move away. C. elegans finds its food by moving around in its environment actively, sometimes even learning the location of food in novel environments after several encounters.
… [T]hese organisms do not seem to exhibit anything that we would want to call behavioral control: they do not inhibit or otherwise control action execution, and what they learn is simply the location toward which to direct their hardwired movements. It is thus unlikely that early bilaterians, as modeled by C. elegans, were goal-directed, decision-making agents, only animate actors.
Then “came the so-called Cambrian explosion and organisms with ‘complex active bodies’ with appendages, teeth, claws, and more that had to be coordinated for effective action.” Competition for food was a major evolutionary event leading to the development of life diversity:
Organisms’ foraging for food became much more uncertain as they began to prey on other highly mobile creatures who could flee or otherwise defend themselves, and they also had to defend against clever predators … To cope with these many and varied challenges, organisms needed a much more complex manner of functioning than C. elegans. They needed not only a larger arsenal of appendages and actions but also more effective ways of controlling their actions flexibly to solve problems in uncertain and dynamically changing circumstances. Enter feedback control organization. These were the first truly agentive organisms, at least in some components of some domains of activity.
Regarding animals exhibiting any form of what could be reasonably described as agency, Tomasello starts with lizards:
We do not know who the first agentive organisms were, but let us fast-forward to some creatures about whom we know much more. From the mélange of species with complex, active bodies emerged the first vertebrates, the fishes, and then some 350 million years ago the first land-based vertebrates, the amphibians, and then the reptiles. Because we have much better behavioral data on reptiles, let us focus our attention on them … [L]izards can learn quickly to solve novel foraging problems, such as removing the lid from a plastic well to retrieve a reward … Global inhibition is likely of special importance when, for example, an individual is in the process of eating and a predator approaches. The individual must then “freeze” its eating behavior. Then, separately, it decides what to do in the new situation (e.g., flee). Global inhibition thus enables goal-directed agents to operate with go-no-go decision-making sequentially across different actions, turning one off and another on as appropriate to the goal and situation … [L]izards make decisions and can inhibit the execution of bad ones, in effect taking a response that was “go” and changing it, in medias res, to “no-go.” … [R]eptiles and many other organisms operate similarly as basic feedback control systems with the same basic structure of goal pursuit, go-no-go decisions (with global inhibition), and discrimination learning. They are operating as goal-directed agents.
Living things evolve to meet challenges or opportunities posed by their environment, and the more rapidly changing the environment, the more adaptive organisms will have to be to survive:
A worm’s experiential niche is basically dirt and bacteria; for the worm, fish and trees and humans simply do not exist, because it has no truck with them. A lizard’s experiential niche, in contrast, comprises ants, crickets, grass, a burrow, and many other things—visually and auditorily registered—because that is what the lizard needs to perceive in its ecological niche to support its foraging and other activities … Along with goal-directed agency, then, comes a fundamental shift in experiential niche. Organisms no longer just perceive attractive and repulsive stimuli; they attend to situations that are relevant for their goal pursuit. Situations that are relevant for their goal pursuit are of two types: (i) opportunities for goal attainment (e.g., the cricket is low in the bush); or (ii) obstacles to goal attainment (e.g., a snake is close by). Opportunities and obstacles are defined, obviously, in terms of the organism’s action capabilities. Goal-relevant opportunities and obstacles for action constitute a completely new type of experiential niche: the agentive niche … Anthropomorphizing the process of evolution by means of natural selection, we may say that to empower organisms to deal effectively with unpredictably changing environments, Nature devised a new way of operating, agency, in which the individual directs its actions flexibly toward goal situations and controls its behavior flexibly via attentionally informed decision-making, which requires it to attend to goal-relevant situations in the environment as either obstacles or opportunities for goal attainment. This is an entirely new type of experiential niche, one that nonagents simply do not experience … Goal-directed, decision-making agents actively seek to fulfill their goals and maintain their reference values by acting on the world; they are doing this basically constantly, even when they are waiting in front of an experimental apparatus for the appearance of food. And goals are not mysterious entities, as behaviorists would have it, but simply off-line perceptions of the world—perceptually imagined situations—that the organism desires or is motivated to bring about. It then behaves until it perceives the realization of those desired situations in the actual world … The foundation stone of behavioral agency is thus feedback control organization, as found in lizards and other goal-directed agents. Goal-directed agents are not just stimulus driven. They direct their actions toward goals, a process that is the sine qua non of intelligent action, because without a goal there can be no sense of effectiveness or success. Goal-directed agents also control their actions via informed decision-making, accompanied by the possibility of inhibiting unwanted actions, leading to new forms of behavioral flexibility. Such informed decision-making requires the individual to attend to situations that are relevant for particular goals as either opportunities or obstacles.
In the next essay in this series, we’ll explore the steps that led to the ability of mammals to engage in a higher level of agency, namely executive function.