Let’s have some fun. Imagine you’re an alien scientist, looking at domesticated humans and animals and their wild counterparts. You have no historical context…just the before-and-after. And your objective is to figure out what kind of selective pressure would explain the shift.
You look at physical changes and note significant brain shrinkage and facial neoteny. You look at behavioral changes and note reduced reactivity (including reactive aggression) and increased compliance. You look at neurological changes and note less vigilance and more dependence. And you look at cognitive changes and note a greater tolerance for contradiction or command. Now you need to reverse-engineer the pressure that accounts for those changes.
You’d conclude that attenuation was being rewarded not for survival, but for something like a tolerance of constraint. Reduced reactivity to imposed conditions that would normally trigger avoidance, protest, flight, or rupture.
In domesticated (civilized) animals and people, it’s clear that attenuation is being rewarded for enabling them to do certain things. Namely, remain in proximity to unpredictable others, function under external control, inhibit instinctual responses to pain, crowding, or contradiction, and perform behaviors for social approval or symbolic reward…not direct need fulfillment.
What if you were pressed to take a shot at describing the environment that produced such a pressure?
If you had no cultural context and just observed the shift, you’d infer something like the following: a system that imposes artificial constraints, limits autonomy, suppresses immediate feedback, and rewards non-disruption. A system that rewards animals that don’t bolt at loud noises, humans who don’t resist moral contradiction, and minds that prioritize external signals (orders, rules, appearances) over internal ones (intuition, emotion, sensory experience). One that filters out traits that protest, question, disrupt, flee, or grieve.
Your hypothesis might be something like, “Attenuation was being selected for to enable life inside an imposed system that contradicts natural feedback.” Of course, that’s the very definition of captivity, domestication…civilization.
Now, you’re handed the conventional narrative. The history and anthropology books. The studies. You’d feel validated somewhat as you read the theory of human self-domestication…a process that “weeded out aggression” in favor of cooperation, social harmony, and prosocial behavior. But you’d also feel something was off. That this framing is deeply incomplete (and dangerously flattening). Because there’s no mention of the actual trade-offs.
Let’s look at the conventional framing of human (self) domestication and see what it gets right.
Anthropologists and evolutionary psychologists argue that early humans began to select against reactive aggression, especially in small bands where group (coalitionary) punishment could be used to ostracize or kill bullies. Over time, this likely contributed to facial feminization, reduced sexual dimorphism (differences between the sexes), and more juvenile (neotenous) behavior…hallmarks of “domestication syndrome.” Also, a reduction in testosterone-linked traits, stress-reactivity, and impulsivity…which likely made groups more stable/cohesive.
What’s this framing missing?
For one, I think it confuses (or leads people to confuse) submission with peace. Just because someone isn’t fighting back doesn’t mean the system is just. A domesticated animal isn’t peaceful, necessarily, it’s conditioned or selected not to protest. Likewise, a “civilized” human isn’t necessarily cooperative…they’re trained to suppress resistance. In other words, to the extent that we eliminated (reactive) aggression…we eliminated resistance to coercion.
And it fails to distinguish between types of aggression. Reactive aggression (fight-or-flight, self-defense, boundary enforcement) was suppressed. Moral aggression (anger in response to injustice, betrayal, or cruelty) was pathologized (too sensitive or oppositional). But instrumental aggression (cold, planned, goal-oriented violence) is clearly rewarded in civilization. To the extent that it “succeeds,” it always has been.
And the conventional explanation for human self-domestication doesn’t seem interested in what was lost. It treats the process as a moral victory. But I don’t think it was “bad behavior” that got weeded out…it was the ability to react honestly to harm. Domestication selected for attenuated perception, emotional buffering, and following symbolic rules…not any kind of inner peace. It reduced reactive violence while it reduced truthful response to violence. And I think the intention (of those driving the domestication process) was in the latter, with the former being largely inadvertent.
Because we know that selecting for one behavioral trait (like tameness or compliance) cascades into structural, cognitive, sensory, and emotional changes. We know this. Traits aren’t modular. They’re entangled…especially when they involve the neural crest.
The neural crest hypothesis of domestication (2014, Wilkins, Wrangham, Fitch) suggests that domestication syndrome in mammals is caused by mild deficits in neural crest cell development during embryogenesis.
The neural crest contributes to all sorts of things…facial morphology (jaw, teeth, skull), adrenal glands (stress response), pigmentation, autonomic nervous system, peripheral nerves and glia, and parts of the limbic system (emotion, reactivity, threat detection).
If you select for tameness (or, in humans, for docility/compliance), you’re not just changing a particular behavior…you’re reconfiguring the organism’s whole developmental trajectory. And here’s what you get:
- Smaller brains
- Flattened faces
- Lower stress reactivity
- Blunted sensory input
- Neoteny (more juvenile traits retained into adulthood)
- Reduced startle or protest response
- Delayed or diminished emotional signaling
Where does that show up in humans? Increased social pliability. Extended childhood dependence. Lower physiological sensitivity. Greater performance tolerance under contradictory or symbolic norms.
In other words, your “modern human” wasn’t just bred to be nice…it was bred to feel less and to respond less to what would once have been danger, injustice, or disorder. That isn’t a linear trade. It’s a network-wide reorganization of the system (what Bateson would call a change in the system’s pattern of constraints).
The First to Fall 