Serotonin's Role in Biological Networking: From Swarm Behavior to Biomimetic Systems

Serotonin's Role in Biological Networking: From Swarm Behavior to Biomimetic Systems

Serotonin's Role in Biological Networking and Swarm Behavior

Serotonin plays a critical role in regulating collective behavior across numerous animal species, functioning as a chemical messenger that can dramatically transform individual behavior to promote group coordination.

The Desert Locust Transformation

The most striking example of serotonin's influence on collective behavior comes from studies of the desert locust (Schistocerca gregaria). These insects normally exist as solitary creatures, avoiding contact with others of their species. However, when environmental conditions force them into proximity, a remarkable transformation occurs:

Within just 2-3 hours of forced crowding, desert locusts undergo a complete behavioral reversal, changing from solitary, shy insects into gregarious members of devastating swarms. This transformation is directly triggered by a sharp increase in serotonin levels within their thoracic ganglia (nerve bundles in their midsection).

The research team led by Michael Anstey at Oxford University and Stephen Rogers at Cambridge University demonstrated that locusts with the highest social tendencies had three times more serotonin than their solitary counterparts. They identified two pathways that trigger this serotonin spike:

1. Mechanical stimulation: When locusts jostle against each other, touch-sensitive hairs on their hind legs stimulate serotonin production.

2. Visual and olfactory cues: The sight and smell of other locusts also trigger serotonin release.

The researchers confirmed serotonin's causal role through a series of elegant experiments:

• Blocking serotonin receptors prevented locusts from becoming gregarious even under crowded conditions

• Applying serotonin directly to a locust's ganglia induced social behavior without any crowding

• Injecting locusts with 5-hydroxytryptophan (the precursor to serotonin) accelerated their transformation to a social state

This serotonin-triggered transformation involves massive physiological changes beyond behavior, including altered coloration (from green to yellow/red), increased muscle development, and changes in metabolism. All of these adaptations support the transition from solitary life to coordinated swarm behavior.

Species Variation: Migratory Locust Contrast

Interestingly, not all locusts respond to serotonin in the same way. The migratory locust (Locusta migratoria) shows an opposite response compared to the desert locust. Research published in the scientific literature revealed that in this species, serotonin actually promotes solitary behavior rather than gregariousness.

This contrasting effect demonstrates that while serotonin is a vital regulator of social behavior across species, its specific effects are adapted to the ecological niche and evolutionary history of each species. Such variation highlights the complexity of neurotransmitter systems in regulating social behavior.

Beyond Locusts: Serotonin in Other Social Species

Serotonin's influence on collective behavior extends well beyond locusts:

In Crayfish and Lobsters: Hierarchy and dominance behaviors are regulated by serotonin levels. Researchers have found that injecting serotonin into subordinate lobsters causes them to adopt dominant postures and behaviors, while octopamine (another neurotransmitter) induces submissive behaviors. This chemical regulation of social hierarchy demonstrates how serotonin shapes complex social structures.

In Social Ants: Serotonin helps regulate division of labor within colonies. Worker ants show different serotonin levels based on their tasks, with foragers typically having higher serotonin levels than nest workers.

In Bees: Serotonin influences aggression and defensive behaviors of honey bees. Guard bees show elevated serotonin levels compared to nurse bees, demonstrating how the neurotransmitter helps regulate specialized roles within the colony.

In Fish Schools: Serotonin levels affect schooling behaviors in various fish species. Higher serotonin promotes tighter schooling formations and more synchronized swimming in species like zebrafish.

These diverse examples illustrate how a single neurotransmitter serves as a fundamental mediator of collective behavior across the animal kingdom, enabling the emergence of complex social structures from simple chemical signaling.

2. Serotonin's Chemical Mechanism and Effects

To understand serotonin's powerful effects on biological networking, we must explore its chemical structure, synthesis pathway, and mechanisms of action at the cellular level.

Chemical Structure and Synthesis

Serotonin (5-hydroxytryptamine or 5-HT) belongs to the monoamine class of neurotransmitters. Its synthesis begins with the essential amino acid tryptophan, which humans and animals must obtain through their diet. The synthesis pathway proceeds through several key steps:

1. Hydroxylation: The enzyme tryptophan hydroxylase adds a hydroxyl group to tryptophan, converting it to 5-hydroxytryptophan (5-HTP). This is the rate-limiting step in serotonin production, meaning it's the slowest step that controls the overall rate of synthesis.

2. Decarboxylation: The enzyme aromatic L-amino acid decarboxylase removes a carboxyl group from 5-HTP, resulting in 5-hydroxytryptamine (5-HT), or serotonin.

This synthesis primarily occurs in two locations:

• The raphe nuclei of the brainstem, which produce serotonin for the central nervous system

• Enterochromaffin cells in the intestinal mucosa, which produce approximately 90% of the body's serotonin

The production of serotonin is tightly regulated by feedback mechanisms that monitor tryptophan availability and serotonin levels, ensuring the body maintains appropriate concentrations of this powerful signaling molecule.

Cellular Mechanisms of Action

Serotonin exerts its effects through a complex family of receptors. Scientists have identified at least 15 different serotonin receptor subtypes, grouped into seven families (5-HT₁ through 5-HT₇) based on their structural and functional characteristics.

When serotonin is released from a neuron, it diffuses across the synaptic cleft (the space between neurons) and binds to specific receptors on the postsynaptic neuron. Depending on the receptor type activated, different intracellular signaling cascades are triggered:

• 5-HT₁ receptors typically inhibit adenylyl cyclase, reducing cyclic AMP (cAMP) production

• 5-HT₂ receptors activate phospholipase C, leading to increased intracellular calcium

• 5-HT₃ receptors are unique as they're the only ionotropic (ion channel) serotonin receptors, allowing direct ion flow

• 5-HT₄, 5-HT₆, and 5-HT₇ receptors stimulate adenylyl cyclase, increasing cAMP production

• 5-HT₅ receptors have less well-understood signaling pathways

This diversity of receptors allows serotonin to exert a wide range of effects depending on which receptors are present in a particular tissue or cell type. In swarm formation, specific receptor subtypes in key ganglia mediate the transition from solitary to social behavior.

Serotonin Signaling in Neural Networks

In neural networks, serotonin acts primarily as an inhibitory neurotransmitter, meaning it typically decreases the likelihood that the receiving neuron will fire an action potential. This inhibitory function is crucial for modulating neural activity and preventing over-excitation.

The serotonergic system in the brain has a distinctive architecture. Serotonergic neurons have their cell bodies clustered in the raphe nuclei of the brainstem, but their axons project widely throughout the brain. This allows a relatively small number of serotonergic neurons to influence activity across multiple brain regions simultaneously. A similar pattern is seen in the thoracic ganglia of insects like locusts, where a limited number of serotonergic neurons can trigger widespread behavioral changes.

After serotonin has transmitted its signal, it is removed from the synapse through:

1. Reuptake: The serotonin transporter (SERT) pumps serotonin back into the presynaptic neuron

2. Degradation: The enzyme monoamine oxidase (MAO) breaks down serotonin into 5-hydroxyindoleacetic acid (5-HIAA)

Both these mechanisms are targets for pharmaceutical interventions. For example, selective serotonin reuptake inhibitors (SSRIs) block SERT, increasing extracellular serotonin levels, while monoamine oxidase inhibitors (MAOIs) prevent serotonin breakdown.

3. Comparison with Other Neurotransmitters

Understanding serotonin's role in biological networking requires comparing it with other major neurotransmitters that also regulate behavior and physiological functions.

Serotonin vs. Dopamine: Complementary Motivational Systems

Serotonin and dopamine often work as complementary systems in regulating behavior:

Dopamine primarily functions as the "reward" neurotransmitter. It is released during pleasurable activities and reinforces behaviors that lead to rewards. Key characteristics include:

• Promotes approach behaviors toward desirable stimuli

• Mediates the pleasure associated with food, sex, and social interaction

• Drives motivation and persistence in goal-directed behavior

• Primarily excitatory in its effects on neural circuits

Serotonin, by contrast, often acts as a behavioral inhibitor:

• Promotes patience and delayed gratification

• Inhibits impulsive responses

• Regulates mood stability rather than euphoria

• Primarily inhibitory in its effects on neural circuits

This complementary relationship is evident in studies of social hierarchy in primates. Dominant individuals typically show elevated dopamine levels associated with their higher social status and access to resources. However, serotonin plays a crucial role in allowing them to maintain that status by inhibiting impulsive aggression that might lead to social conflict.

In locusts, this relationship manifests differently. The transformation from solitary to gregarious behavior involves not just increased serotonin but also changes in dopamine signaling that drive the locusts to actively seek out conspecifics rather than avoid them.

Serotonin vs. Norepinephrine: Stress and Arousal

Norepinephrine (also called noradrenaline) is another monoamine neurotransmitter with important distinctions from serotonin:

Norepinephrine is primarily associated with:

• The "fight-or-flight" response

• Increased alertness and arousal

• Focused attention

• Rapid response to threats

• Primarily excitatory effects

Serotonin in this context functions to:

• Modulate stress responses

• Prevent excessive emotional reactivity

• Promote adaptability to chronic stress

• Regulate recovery after stress

Research with mice and rats has shown distinct patterns of change in serotonin and norepinephrine in response to stress. When exposed to restraint stress, both species showed decreased serotonin in the locus coeruleus (a key noradrenergic nucleus) and increased dopaminergic activity in the hypothalamus. However, serotonin turnover increased in the amygdala, potentially moderating the fear response.

In human disorders like depression and anxiety, the balance between these systems is often disrupted. This has led to the development of dual-action antidepressants that target both serotonin and norepinephrine, such as serotonin-norepinephrine reuptake inhibitors (SNRIs).

Evolutionary Perspectives: Neurotransmitter Profiles Across Species

The balance of neurotransmitters varies significantly across species and appears to have played a role in evolutionary adaptations:

Human brains show dramatically higher dopamine levels compared to other primates, while sharing similar serotonin profiles. This neurochemical distinction may have contributed to humans' exceptional social cooperation capabilities. Dopamine's role in social reward may have enabled humans to derive greater pleasure from cooperative activities, facilitating the development of complex societies.

In invertebrates like C. elegans (roundworms), serotonin signals food availability. When a well-fed worm encounters bacteria (its food source), dopamine is released to slow it down. If the worm is starved, serotonin is also released, further slowing the animal to maximize time spent near food. This demonstrates how these neurotransmitters work together to regulate adaptive behaviors.

In insects like locusts, the balance shifts dramatically during phase transition from solitary to gregarious forms. The migratory locust (Locusta migratoria) shows a different relationship between serotonin and dopamine than the desert locust (Schistocerca gregaria), reflecting their different ecological niches and swarming behaviors.

These comparative examples illustrate how neurotransmitter systems have been adapted throughout evolution to serve specific behavioral and ecological needs, with serotonin consistently playing a central role in social regulation across diverse species.

4. Serotonin's Effects on Human Cognition and Function

In humans, serotonin exerts profound and wide-ranging effects on cognition, emotion, and physiological function, making it a central player in both normal psychological functioning and psychiatric disorders.

Mood Regulation and Emotional Processing

Serotonin's most well-known role in humans is its influence on mood and emotional state:

Depression and Anxiety: Low serotonin activity has been linked to depression and anxiety disorders. While the "serotonin deficiency" theory of depression has been refined in recent years to acknowledge the complexity of mood disorders, medications that increase serotonin availability (like SSRIs) remain effective treatments for many patients.

Emotional Resilience: Serotonin promotes emotional resilience and adaptability to stress. People with optimal serotonin function typically show greater capacity to recover from negative emotional states and maintain positive mood in the face of challenges.

Emotional Processing: Serotonin modulates how we process emotional information. Research using brain imaging has shown that serotonin affects activity in the amygdala (involved in processing fear and threat) and the prefrontal cortex (involved in emotional regulation).

A fascinating real-world example comes from studies of financial decision-making. Traders in financial markets with optimal serotonin function showed better decision-making under stress and were less likely to exhibit the "disposition effect" (holding onto losing investments too long while selling winners too quickly), a common cognitive bias in financial decision-making.

Cognitive Function and Learning

Beyond emotion, serotonin influences various aspects of cognitive function:

Memory Formation: Serotonin modulates memory formation and retrieval, particularly for emotionally-laden information. It helps determine which experiences are encoded into long-term memory, with potential implications for understanding PTSD and other trauma-related disorders.

Cognitive Flexibility: Optimal serotonin function promotes cognitive flexibility—the ability to adapt thinking and behavior to changing circumstances. Studies have shown that serotonergic drugs can enhance reversal learning (the ability to update behavior when reward contingencies change).

Attention and Focus: Serotonin interacts with other neurotransmitters like norepinephrine and acetylcholine to regulate attention. Disruptions in this balance contribute to attention disorders.

A compelling example of serotonin's cognitive effects comes from studies of MDMA (ecstasy), which causes massive serotonin release. MDMA not only induces positive mood but also increases empathy and social connection, illustrating serotonin's role in social cognition. This finding has led to clinical trials of MDMA-assisted psychotherapy for PTSD, where enhanced emotional processing may facilitate trauma recovery.

Physiological Functions Beyond the Brain

While most famous for its psychological effects, serotonin regulates numerous physiological functions throughout the body:

Digestive System: About 90% of the body's serotonin is produced in the gut, where it regulates intestinal motility, secretion, and sensitivity. Irritable Bowel Syndrome (IBS) involves disrupted serotonin signaling, and drugs targeting 5-HT3 and 5-HT4 receptors are used to treat various gastrointestinal disorders.

Sleep Regulation: Serotonin is a precursor to melatonin, the hormone that regulates sleep-wake cycles. The raphe nuclei that produce brain serotonin are also involved in regulating the transition between sleep stages. This explains why serotonergic antidepressants often affect sleep patterns, sometimes improving sleep architecture in depression.

Appetite Control: Serotonin suppresses appetite, particularly for carbohydrates. This effect has been leveraged in weight-loss medications, though with mixed success due to side effects.

Pain Perception: Serotonin modulates pain signaling in the spinal cord and brain. It's involved in both pain inhibition (descending pain control) and pain facilitation in different contexts. This dual role explains why serotonergic drugs can sometimes help with pain conditions like fibromyalgia.

Bone Health: Surprisingly, serotonin affects bone metabolism. Gut-derived serotonin inhibits bone formation, while brain-derived serotonin promotes it. This discovery has led to investigation of serotonin modulators as potential treatments for osteoporosis.

A dramatic example of serotonin's multiple physiological effects is seen in carcinoid syndrome, a rare condition where tumors produce excessive serotonin. Patients experience flushing, diarrhea, heart valve damage, and wheezing—illustrating how one chemical messenger affects multiple organ systems.

5. Serotonin and Network Theory

Serotonin's role in coordinating behavior across individuals and systems provides valuable insights into network theory, collective intelligence, and self-organizing systems.

Serotonin as a Network Modulator

At its core, serotonin functions as a network modulator—it adjusts the connectivity and responsiveness of neural networks rather than simply exciting or inhibiting them:

Neural Plasticity: Serotonin promotes neural plasticity, the ability of neural connections to strengthen or weaken based on activity. Through its effects on long-term potentiation and depression (cellular mechanisms of learning), serotonin allows networks to reconfigure based on experience.

Network Synchronization: Serotonin influences the synchronization of neural firing, especially in oscillatory networks involved in memory and attention. This synchronizing effect may explain how serotonin coordinates activity across brain regions.

Connectivity Balance: Serotonin helps maintain balance between excitatory and inhibitory connections in neural networks. This is crucial for network stability and preventing pathological states like seizures.

In computer science terms, serotonin acts like an adaptive parameter that adjusts network properties based on conditions. It's analogous to "temperature" in simulated annealing algorithms or "learning rate" in neural networks—a meta-parameter that determines how readily the network changes in response to new inputs.

Emergence of Collective Behavior

The dramatic transformation of locusts from solitary to gregarious forms provides a perfect case study in emergence—the appearance of complex, coordinated behaviors from simple interactions:

Threshold Effects: In locust swarms, a critical density of individuals must be reached before serotonin-mediated transformation begins. Once this threshold is crossed, the transformation accelerates as more individuals change, creating a positive feedback loop.

Local Rules, Global Patterns: Each locust responds only to local stimuli (touching neighboring insects), yet this produces globally coordinated movement patterns in swarms of billions.

Phase Transitions: The shift from solitary to gregarious behavior represents a phase transition, similar to water turning to ice. Small quantitative changes in serotonin levels produce qualitative changes in behavior once a threshold is crossed.

The power of such emergence is evident in the devastating economic impact of locust swarms, which can consume their own weight in food daily. A swarm containing billions of insects can devastate crops across vast regions—a global effect emerging from local chemical changes in individual insects.

Network Resilience and Adaptation

Serotonergic systems contribute to network resilience—the ability to maintain function despite perturbations:

Homeostatic Regulation: Serotonin systems typically show robust homeostatic regulation, with multiple feedback mechanisms maintaining appropriate signaling levels. This allows neural networks to maintain stable function despite changing conditions.

Adaptive Responses: Serotonergic signaling adapts to chronic conditions. For example, chronic stress initially increases serotonin signaling, but over time leads to receptor downregulation that preserves network function.

Diverse Receptor Distribution: The wide distribution of different serotonin receptor subtypes creates redundancy in the system. If one pathway is disrupted, others can often compensate.

A dramatic example of this resilience comes from studies of MDMA users. Despite massive serotonin release that temporarily depletes stores, most users' serotonin systems recover normal function after abstinence. However, very heavy use can exceed the system's resilience, causing long-term changes in serotonergic function.

6. Principles for Biomimetic Digital Systems

The serotonergic mechanisms that coordinate biological networks offer rich inspiration for designing artificial systems with collective intelligence.

Distributed Control Through Chemical Messaging

Biological swarms achieve coordination without centralized control, primarily through chemical messengers like serotonin. This principle can be adapted to digital systems:

Digital Pheromones: Virtual agents can use digital "pheromones" that influence neighboring agents, creating emergent coordination. This approach has been implemented in swarm robotics, where robots leave virtual traces that influence others' movement decisions.

Stigmergy: In ant colonies, individuals modify their environment (through pheromones) in ways that influence others' behavior. Digital systems can implement stigmergic coordination through shared environmental variables that agents can both read and modify.

Concentration-Dependent Effects: Like serotonin's concentration-dependent effects, digital agents can respond differently to signal strength, with threshold effects triggering qualitative behavior changes.

A practical example is the "Ant Colony Optimization" algorithm, which uses digital pheromones to solve complex problems like routing in telecommunications networks. Agents (virtual ants) deposit digital pheromones proportional to the quality of solutions they find, gradually leading the swarm toward optimal solutions without centralized control.

Adaptive Thresholds and Phase Transitions

Serotonin triggers phase transitions in locust behavior when concentrations cross critical thresholds. This principle offers powerful design ideas:

Dynamic Thresholds: Systems can implement adaptive thresholds that change based on experience. For example, network security systems might adjust threat detection thresholds based on historical patterns.

Controlled Phase Transitions: Digital systems can be designed to undergo coordinated phase transitions when conditions warrant, rapidly switching from one operating mode to another.

Hysteresis Effects: Biological serotonin systems often show hysteresis—where the threshold for inducing a change differs from the threshold for reversing it. This prevents rapid oscillation between states and can be valuable in digital systems.

Amazon's warehouse robots demonstrate these principles, using algorithms inspired by insect swarms. Robots coordinate through digital signals that change their behavior based on warehouse conditions, with different thresholds triggering different movement patterns as order volume fluctuates.

Multi-modal Signaling for Robust Coordination

Serotonin acts alongside other neurotransmitters in biological systems, creating robust, multi-faceted signaling:

Complementary Signals: Digital systems can implement multiple signaling mechanisms that serve complementary functions, analogous to serotonin and dopamine's complementary roles.

Redundant Channels: Critical coordination can be ensured through redundant signaling pathways, similar to how multiple serotonin receptor subtypes provide redundancy in biological systems.

Cross-Modal Reinforcement: Different signaling modes can reinforce each other, increasing system reliability when signals are consistent and flagging potential problems when they conflict.

Google's traffic routing in Maps exemplifies these principles. The system uses multiple data sources (GPS locations, historical patterns, user reports) as complementary signals to determine traffic conditions. When signals align, confidence increases; when they conflict, the system can apply different weighting or seek additional data.

Self-Organization and Emergent Problem Solving

Perhaps the most powerful principle from serotonergic networks is their ability to enable self-organization and emergent problem-solving:

Local Optimization, Global Solutions: Individual agents making locally optimal decisions based on limited information can collectively solve complex global problems.

Diversity of Response Patterns: Different agents can respond to the same signals differently based on their state or role, creating functional specialization without explicit programming.

Positive Feedback Loops with Constraints: Positive feedback (like the cascade of serotonin-mediated changes in locust swarms) drives rapid system adaptation, while regulatory mechanisms prevent runaway processes.

Tesla's distributed fleet learning demonstrates these principles. Individual vehicles collect local driving data, which collectively trains autonomous driving algorithms. The system emerges more capable than any individual contributor, adapting to new driving conditions through distributed optimization.

7. Serotonin in Microorganisms: From Biosynthesis to Ecological Interactions

Serotonin's presence and functions in microorganisms represent one of the most fascinating yet understudied aspects of this versatile molecule, revealing its deep evolutionary roots and ecological importance.

Serotonin in Bacteria

While not all bacteria produce serotonin, several species have demonstrated the capability:

Biosynthetic Pathways: The mechanisms of bacterial serotonin production differ from those in plants and animals. Some bacteria, like certain strains of Escherichia coli and Streptococcus species, can synthesize serotonin de novo from tryptophan, though through pathways that often involve novel or promiscuous enzymes not found in eukaryotes. In many cases, bacterial tryptophan decarboxylases (enzymes that primarily function in amino acid metabolism) show surprising side activity in converting tryptophan to tryptamine, the precursor to serotonin.

Functional Roles in Bacterial Physiology: In bacteria that produce it, serotonin appears to serve several adaptive functions:

• Oxidative Stress Protection: As in other organisms, serotonin's antioxidant properties help bacteria neutralize reactive oxygen species. This may have been one of its earliest evolutionary functions, emerging when Earth's atmosphere became increasingly oxygenated.

• UV Radiation Defense: Some bacteria increase serotonin production when exposed to UV radiation, suggesting a protective role against DNA damage, similar to what has been observed in yeast.

• Intercellular Communication: Emerging evidence indicates that serotonin may function as a bacterial signaling molecule, particularly in dense bacterial communities. Recent research has discovered that serotonin can activate bacterial quorum sensing systems in some pathogenic bacteria, including Pseudomonas aeruginosa. When exposed to serotonin, these bacteria increase virulence factor production and biofilm formation, suggesting that they can detect and respond to host-derived serotonin as an environmental cue.

• Environmental Adaptation: Fluctuations in bacterial serotonin production have been observed in response to changing environmental conditions, suggesting a role in adaptive responses to environmental stressors.

Conclusion: The Future of Serotonin-Inspired Systems

The study of serotonin in biological networks opens exciting frontiers for both neuroscience and artificial intelligence.

Therapeutic Applications

Understanding serotonin's role in coordinating biological networks has already yielded valuable therapeutic approaches:

Novel Psychiatric Medications: Beyond traditional SSRIs, researchers are developing drugs targeting specific serotonin receptor subtypes for more precise effects on mood, anxiety, and cognition.

Gut-Brain Axis Interventions: Recognition of serotonin's role in gut-brain communication has spawned new approaches to treating conditions like IBS that involve both psychological and gastrointestinal symptoms.

Social Functioning Therapies: Research on serotonin's role in social behavior has informed treatments for conditions involving social dysfunction, from autism to social anxiety disorder.

Advanced Artificial Intelligence Applications

Serotonin-inspired design principles are finding their way into artificial intelligence:

Swarm Intelligence Algorithms: Systems modeled on locust swarm coordination are solving complex optimization problems in fields from logistics to financial modeling.

Adaptive Neural Networks: Neural network architectures that incorporate serotonin-like modulatory signals show enhanced adaptability and learning capabilities.

Human-AI Collaborative Systems: Understanding how serotonin facilitates human social coordination informs the design of AI systems that collaborate effectively with humans.

Future Research Directions

The frontier of serotonin research promises further insights for both biology and technology:

Precision Mapping of Serotonergic Circuits: New technologies like optogenetics are enabling precise mapping of how serotonin shapes neural networks in real-time.

Evolutionary Comparative Studies: Examining serotonin's role across species reveals how this ancient signaling system has been adapted for different ecological niches.

Hybrid Bio-Digital Systems: Emerging technologies may enable direct interfaces between biological serotonergic systems and digital networks, creating unprecedented hybrid systems.

As we continue to unravel the intricate ways serotonin coordinates biological networks, we gain not only deeper understanding of our own biology but also powerful design principles for the next generation of intelligent systems. From the humble locust swarm to the complexities of human consciousness, serotonin exemplifies how simple chemical signals can orchestrate the most sophisticated emergent behaviors in nature—a lesson with profound implications for the future of technology.