New research published on December 19, 2025, in the esteemed journal Science Advances has illuminated a fundamental evolutionary strategy employed by ant species: a strategic reduction in the individual robustness of workers to foster the growth of larger, more complex colonies. This groundbreaking study posits that by investing less in the protective cuticle – the hard outer layer of their exoskeleton – ants free up vital nutrients, enabling the production of a greater number of workers. This evolutionary pivot from heavily armored individuals to a numerous, less-protected workforce has been identified as a key driver behind the extraordinary ecological success and diversification of ants, a pattern that resonates across the spectrum of complex societies, including those formed by humans.
The Enduring Biological Dilemma: Quantity Versus Quality
The tension between investing in individual quality versus producing a greater quantity of individuals is a pervasive theme in biology, influencing everything from reproductive strategies to the development of complex social structures. For solitary organisms, individual strength and resilience are paramount for survival against predators, environmental stressors, and disease. However, as species evolve towards sociality, the calculus often shifts. The needs of the collective can begin to outweigh the imperative for individual self-sufficiency, leading to fascinating evolutionary compromises.
This principle is at the heart of the latest findings. As Professor Evan Economo, chair of the Department of Entomology at the University of Maryland and a senior author of the study, explains, "There’s this question in biology of what happens to individuals as societies they are in get more complex. For example, the individuals may themselves become simpler because tasks that a solitary organism would need to complete can be handled by a collective." In this context, individuals can become what scientists term "cheaper" – requiring fewer resources to develop and thus producible in larger numbers, even if each unit is individually less robust. This concept, while long hypothesized, lacked comprehensive empirical validation in large-scale analyses of social insects until now. Economo, who also holds the James B. Gahan and Margaret H. Gahan Professorship at UMD, emphasized the novelty of this large-scale testing.
Ants: A Premier Model for Social Evolution
Ants present an unparalleled natural laboratory for investigating the intricacies of social evolution. Their societies exhibit an astonishing spectrum of complexity, ranging from small, relatively simple colonies comprising mere dozens of individuals to supercolonies numbering in the millions, spanning vast geographical areas. This remarkable diversity in social organization, coupled with their ubiquitous presence across nearly every terrestrial ecosystem on Earth, makes them an ideal model system for understanding the fundamental biological strategies that underpin the rise of complex animal societies.
"Ants are everywhere," notes lead author Arthur Matte, a Ph.D. student in zoology at the University of Cambridge, whose work on this project began during his master’s program internship in Economo’s lab at the Okinawa Institute of Science and Technology in Japan. "Yet the fundamental biological strategies which enabled their massive colonies and extraordinary diversification remain unclear." The research team meticulously hypothesized that a crucial, yet overlooked, factor linking colony size to evolutionary success might be the degree to which ants invest in their protective cuticle.
The Energetic Cost of Building Body Armor
The cuticle, an ant’s primary defense, is a complex, multi-layered extracellular matrix that serves several critical functions. It provides a robust physical barrier against predators, pathogens, and desiccation (drying out). Beyond protection, it offers structural support for muscle attachment, enabling movement and exertion. Chemically, the insect cuticle is predominantly composed of chitin, a tough polysaccharide, embedded in a matrix of proteins and lipids, often cross-linked and sometimes sclerotized (hardened) by the incorporation of various minerals, particularly calcium carbonate.
However, constructing and maintaining such an intricate biological armor is energetically and nutritionally expensive. The synthesis of chitin, proteins, and the subsequent sclerotization processes demand significant quantities of limited resources, including nitrogen, amino acids, and various minerals. Producing a thicker, more resilient cuticle necessitates a greater allocation of these precious resources, which directly impacts the total biomass and number of individuals a colony can sustain. A colony’s resource budget is finite; every gram of nitrogen or calcium invested in hardening one individual’s exoskeleton is a gram that cannot be used to produce another worker, lay more eggs, or fuel colony growth. This inherent trade-off forms the crux of the study’s investigation.
Unveiling the Evolutionary Pattern: Methodology and Findings
To empirically test their hypothesis, the researchers undertook an ambitious large-scale analysis. They meticulously examined a vast dataset comprising 3D X-ray micro-computed tomography (micro-CT) scans from over 500 distinct ant species. This advanced imaging technique allowed for precise, non-destructive measurements of both the total body volume and, crucially, the cuticle volume for each individual ant.
Their analysis revealed a striking variability in cuticle investment across species, ranging from a mere 6% to a substantial 35% of an ant’s total body volume. This wide range underscored the evolutionary flexibility in this trait. When these precise morphological measurements were integrated into sophisticated evolutionary models, a clear and compelling trend emerged: ant species that demonstrated a lower proportional investment in their cuticle consistently tended to form larger colonies. This statistical correlation provided robust evidence for the proposed quantity-over-quality strategy. The models demonstrated that this reduced individual armor was not merely a passive correlation but an active evolutionary pathway enabling the proliferation of individuals and the expansion of colony size.
The Collective Advantage: How "Squishier" Ants Thrive
While a thinner cuticle undeniably leaves individual ants more vulnerable to direct threats, the study’s authors propose that this apparent individual weakness is profoundly offset by the emergent strength of a larger, more coordinated collective. This reduction in individual armor, they argue, is not an isolated trait but part of a syndrome of adaptations that facilitate and reinforce advanced social behaviors.
These behaviors include highly cooperative foraging strategies, where numerous workers can overwhelm food sources or quickly transport resources back to the nest. More importantly, shared nest defense becomes significantly more effective with a larger workforce. A multitude of less-armored ants can collectively repel or overwhelm a predator that a smaller number of heavily armored individuals might struggle against. Furthermore, advanced division of labor, a hallmark of complex societies, becomes more pronounced and efficient in larger colonies. Specialized tasks, from brood care to foraging, defense, and waste management, can be distributed among a greater number of individuals, optimizing overall colony productivity and resilience.
Arthur Matte eloquently captures this shift: "Ants reduce per-worker investment in one of the most nutritionally expensive tissues for the good of the collective. They’re shifting from self-investment toward a distributed workforce, resulting in more complex societies." He draws a powerful parallel, noting, "It’s a pattern that echoes the evolution of multicellularity, where cooperative units can be individually simpler than a solitary cell, yet collectively capable of far greater complexity." This analogy underscores a fundamental principle in evolutionary biology: increasing complexity at a higher level of organization (colony or organism) can be achieved through the simplification and specialization of its constituent units (individual ants or cells).
Professor Economo playfully termed this phenomenon "the evolution of squishability," a concept that many children who have interacted with insects can intuitively grasp. The observation that not all insects possess the same degree of physical robustness aligns perfectly with the study’s findings, indicating a diverse range of evolutionary pressures and solutions.
Accelerated Diversification: A Marker of Evolutionary Success
Beyond simply enabling larger colonies, the research uncovered another critical advantage associated with lower cuticle investment: a significantly higher rate of diversification. In evolutionary biology, diversification, which measures the frequency at which new species arise within a lineage, is a key indicator of evolutionary success and adaptability. Professor Economo highlighted the particular significance of this finding, noting that "very few traits have been connected to diversification in ants," making this result especially striking in the field of myrmecology.
The exact mechanisms by which reduced cuticle investment promotes speciation are still being explored, but the researchers put forth compelling hypotheses. One leading idea revolves around ecological versatility. Ants with lower nutritional demands for cuticle production require fewer resources to build their bodies. This "cheaper" construction cost could make them more adaptable to a wider array of environments, particularly those where resources are scarce or unpredictable. "Requiring less nitrogen could make them more versatile and able to conquer new environments," Matte explains, suggesting that this adaptability could facilitate range expansion and the colonization of new ecological niches, which are often precursors to speciation.
The authors also propose a reinforcing feedback loop: as ant societies evolved greater complexity, their group-level defenses – such as collective nest protection, advanced alarm systems, and sophisticated disease control mechanisms – reduced the selective pressure for individual workers to possess heavy, expensive armor. This, in turn, allowed for further reductions in cuticle investment, enabling colonies to grow even larger. Larger colonies then further enhance collective defenses and social functions, completing a positive feedback cycle that drives both increased colony size and potentially, accelerated diversification into new ecological roles and habitats. This dynamic interplay between individual investment and collective advantage paints a vivid picture of evolutionary innovation.
While the study focused on ants, the researchers acknowledge that other social organisms, such as termites, may have followed similar evolutionary trajectories. However, further comparative studies are needed to fully explore this intriguing possibility.
Broader Implications: Lessons from Ants for Humanity
The implications of this research extend far beyond the realm of entomology, offering profound insights into the fundamental principles governing the evolution of complex societies, including human ones. The researchers draw compelling parallels to human history, particularly in military strategy. Historically, heavily armored individual combatants, like medieval knights, represented the "quality" paradigm. However, over time, military tactics evolved to favor larger numbers of specialized, less individually protected soldiers, such as archers, crossbowmen, and later, firearms-wielding infantry. This shift allowed for greater numerical superiority, tactical flexibility, and collective firepower, often overwhelming smaller, albeit individually stronger, forces.
Professor Economo specifically points to Lanchester’s Laws, a set of mathematical equations developed during World War I to model the outcomes of military engagements. These laws demonstrate how a larger force, even if composed of individually weaker units, can exponentially increase its combat effectiveness against a smaller, stronger force, illustrating the power of numerical superiority – a direct echo of the ant’s strategy.
Arthur Matte encapsulates the universal relevance of the findings: "The tradeoff between quantity and quality is all around. It’s in the food you eat, the books you read, the offspring you want to raise." He reflects on the journey, stating, "It was fascinating to retrace how ants handled it through their long evolution. We could see lineages taking different directions, being shaped by different constraints and environments, and ultimately giving rise to the extraordinary diversity we observe today."
This research, titled "The evolution of cheaper workers facilitated larger societies and accelerated diversification in ants," published in Science Advances on December 19, 2025, represents a significant step forward in understanding the intricate dance between individual biology and collective success in the grand tapestry of evolution. It underscores how what appears to be an individual weakness can, through the alchemy of sociality, become a cornerstone of evolutionary triumph.
This research was generously supported by the Okinawa Institute of Science and Technology, the Japan Society for the Promotion of Science KAKENHI (24K01785), the University of Cambridge, and the General Research Fund 2022/2023 (17121922) from the Research Grant Council of Hong Kong. It is important to note that this article does not necessarily reflect the views of these funding organizations.
