A groundbreaking study published in the journal Science Advances on December 19, 2025, reveals a fundamental evolutionary strategy that has driven the success of complex animal societies: a strategic trade-off between individual robustness and sheer numbers. The research, focusing on ants, suggests that prioritizing the production of a greater quantity of less physically formidable workers, rather than a smaller contingent of heavily armored individuals, has been a remarkably successful evolutionary blueprint, particularly in the development of intricate social structures. This discovery offers profound insights into how individuals can adapt and change as societies, including human ones, grow in complexity.
The Ant Colony: A Microcosm of Social Evolution
The question of how individual traits evolve within increasingly complex social systems is a long-standing puzzle in biology. As Evan Economo, senior author and chair of the Department of Entomology at the University of Maryland, 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." This concept, termed "cheaper" individuals in scientific parlance, signifies organisms that require fewer resources for their construction and can therefore be produced in greater abundance, even at the cost of diminished individual physical resilience.
"That idea hasn’t been explicitly tested with large-scale analyses of social insects until now," added Economo, who also holds the prestigious James B. Gahan and Margaret H. Gahan Professorship at UMD. Ants, with their vast range in colony sizes—from a few dozen to millions—and their ubiquity across the globe, present an unparalleled model for investigating the evolutionary pathways of social complexity. "Ants are everywhere," stated lead author Arthur Matte, a Ph.D. student in zoology at the University of Cambridge. "Yet the fundamental biological strategies which enabled their massive colonies and extraordinary diversification remain unclear."
The research team hypothesized that a key factor linking colony size to evolutionary success might be the investment ants make in their cuticle.
The Cost of Body Armor: Cuticle Investment in Ants
The cuticle, the rigid outer layer of an insect’s exoskeleton, is critical for survival. It provides essential protection against predators, dehydration, and disease, while also serving as the structural framework for muscle attachment. However, producing a robust cuticle is a metabolically expensive endeavor, demanding significant amounts of finite nutrients like nitrogen and various minerals. A thicker cuticle necessitates a greater allocation of these resources, inherently limiting the number of individuals a colony can sustain.
This fundamental biological constraint, the researchers proposed, could be a decisive factor in shaping colony size and, consequently, the evolution of social complexity.
Quantifying the Trade-off: A Global Ant Census
To empirically test their hypothesis, the research team embarked on an ambitious data-gathering initiative. They meticulously analyzed a comprehensive dataset comprising 3D X-ray scans of over 500 ant species, a significant sample representing a substantial portion of the ant world’s diversity. This extensive collection allowed for precise measurements of both total body volume and cuticle volume for each species.
The findings were compelling. Investment in the cuticle, as a proportion of an ant’s total body mass, exhibited remarkable variation, ranging from a modest 6% to a substantial 35%. When these detailed morphological data were integrated into sophisticated evolutionary models, a clear and consistent trend emerged: ant species that allocated a smaller percentage of their body mass to cuticle development were overwhelmingly associated with the formation of larger, more populous colonies.
"This quantitative analysis provides the first large-scale empirical evidence for the ‘cheaper worker’ hypothesis in social insects," noted Matte. "It demonstrates a tangible evolutionary mechanism by which ant societies could scale up."
Implications for Societal Growth
The study’s implications extend far beyond the intricate world of ants. The observed trade-off between individual investment in defense and the capacity for larger group formation resonates with broader principles of social evolution. When individual ants possess thinner cuticles, they become more vulnerable in isolation. However, the researchers posit that this vulnerability is mitigated and, in fact, leveraged by the development of enhanced collective behaviors.
"Reduced armor may go hand in hand with other helpful social traits, including cooperative foraging, shared nest defense, and division of labor, all of which tend to become more pronounced as colonies grow," the study authors suggest. This shift represents a profound evolutionary strategy: "Ants reduce per-worker investment in one of the most nutritionally expensive tissues for the good of the collective," Matte explained. "They’re shifting from self-investment toward a distributed workforce, resulting in more complex societies. 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."
Diversification: A Tangible Outcome of Reduced Investment
Beyond facilitating larger colony sizes, the research uncovered another striking correlation: lower investment in the cuticle was also linked to significantly higher rates of diversification. In evolutionary biology, diversification—the process by which new species arise—is widely regarded as a key indicator of evolutionary success and adaptability.
"The fact that we found such a strong link between reduced cuticle investment and increased diversification is particularly significant," stated Economo. "Very few traits have been connected to diversification in ants, making this result especially striking and potentially pointing to a fundamental driver of ant speciation."
Unraveling the Speciation Mechanism
The precise mechanisms by which reduced cuticle investment promotes speciation remain an active area of investigation, but the researchers propose a leading hypothesis: ants with lower nutritional requirements, owing to less robust cuticles, may be better equipped to colonize and thrive in environments where resources are scarce.
"Requiring less nitrogen could make them more versatile and able to conquer new environments," said Matte, reflecting on the genesis of this research. He began this line of inquiry during his master’s program while interning in Economo’s lab at the Okinawa Institute of Science and Technology in Japan. This adaptability could allow previously resource-limited populations to expand their ecological niches, leading to reproductive isolation and the eventual formation of new species.
Furthermore, the study suggests a reinforcing feedback loop: as ant societies evolve greater complexity, collective defense strategies, such as coordinated nest protection and sophisticated disease control mechanisms, diminish the selective pressure for heavily armored individuals. This creates an environment where thinner cuticles are not only tolerated but potentially advantageous. Lower cuticle investment enables colonies to grow larger, and larger colonies, in turn, further reduce the individual need for robust physical defenses.
Economo humorously summarized this phenomenon as "the evolution of squishability," noting that many children discover that not all insects are equally robust.
Broader Implications: From Ants to Humans
The principles illuminated by this ant-centric research have far-reaching implications, extending beyond the insect kingdom and offering compelling parallels to human history and societal development. The researchers draw a direct comparison to human military evolution, where the era of heavily armored knights eventually gave way to the dominance of specialized, numerous soldiers such as archers and crossbowmen. This historical shift underscores a similar trade-off between individual defensive strength and the strategic advantage of overwhelming numbers.
Economo also referenced Lanchester’s Laws, a set of mathematical equations developed during World War I to analyze combat effectiveness. These laws demonstrate how, under certain conditions, large numbers of less powerful combatants can overcome a smaller force of superior fighters. This mathematical framework provides a quantitative understanding of the same quantity-versus-quality dynamic observed in ant societies.
"The trade-off between quantity and quality is all around us. It’s in the food you eat, the books you read, the offspring you want to raise," Matte observed. "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."
A Foundation for Future Research
The study, "The evolution of cheaper workers facilitated larger societies and accelerated diversification in ants," published in Science Advances on December 19, 2025, represents a significant advancement in our understanding of social evolution. Future research will undoubtedly explore whether similar evolutionary strategies have shaped other complex social organisms, such as termites, and delve deeper into the specific genetic and physiological mechanisms underpinning these trade-offs.
This research was made possible through support from 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. While this article reflects the findings of the study, it does not necessarily represent the views of these supporting organizations. The enduring legacy of this work lies in its profound demonstration that in the grand theater of evolution, sometimes, more is indeed more.
