In a fascinating twist on survival of the fittest, groundbreaking research reveals that the overwhelming success of ants stems not from building tougher individuals, but from making them cheaper and more expendable. A study published on December 19 in the journal Science Advances demonstrates that many ant species have flourished by deliberately scaling back on individual protective armour. This strategic shift allowed them to channel precious resources into producing vastly larger colonies, fostering greater cooperation and enabling domination across diverse environments.
The Quantity Over Quality Trade-off
The research, led by scientists from the University of Cambridge and the University of Maryland, centres on the ant's cuticle—the hard, outer layer of its exoskeleton that acts as body armour. This shield protects against predators, dehydration, and disease, but it comes at a steep metabolic cost, requiring scarce nutrients like nitrogen and minerals.
The team analysed 3D X-ray scans from over 500 ant species, measuring the volume of their bodies dedicated to this protective cuticle. The variation was striking: in some species, the cuticle accounted for a mere 6% of body volume, while in others, it comprised up to 35%. When these figures were mapped against colony sizes, a clear evolutionary pattern emerged.
Species that invested less in individual cuticle consistently formed larger, more populous colonies. This highlights a fundamental biological trade-off: building heavily armoured workers limits how many a colony can sustain, while producing 'cheaper', less-protected individuals allows for exponential growth in numbers.
Strength Through Collective Simplicity
Senior author Evan Economo, chair of Entomology at the University of Maryland, explained the core concept. "As societies become more complex, the individuals may themselves become simpler because tasks a solitary organism would need to complete can be handled by a collective," he stated. In evolutionary terms, individuals become 'cheaper' to produce, enabling their mass manufacture even if they are less robust alone.
Lead author Arthur Matte, a PhD student at the University of Cambridge, drew a parallel to the evolution of multicellular life. "Cooperative units can be individually simpler than a solitary cell, yet collectively capable of far greater complexity," he said. For ants, reducing per-worker investment in one of the most nutritionally expensive tissues—the cuticle—fuelled the rise of a distributed workforce and more intricate societies.
This vulnerability at the individual level is powerfully offset by collective behaviours. Larger colonies leverage coordinated nest defence, sophisticated foraging, and a refined division of labour, making the group, not the individual, the primary unit of survival.
A Catalyst for Evolutionary Diversification
One of the study's most significant findings was a link between reduced cuticle investment and higher rates of diversification—a key measure of evolutionary success. Ant lineages that built cheaper, less-armoured workers tended to give rise to new species more frequently.
The reasons behind this accelerated speciation are multifaceted. Arthur Matte suggested that ants with lower nutritional demands, particularly for nitrogen, could thrive in resource-scarce environments, making them more versatile colonisers of new habitats. Another compelling theory is that as colonies grew larger and more complex, group-level defences—like collective nest protection and social 'immunity'—reduced the evolutionary pressure on each ant to be heavily armoured.
This may have created a self-reinforcing cycle: cheaper workers allow for larger colonies, and larger colonies, with their collective security, further diminish the need for individual fortification. Evan Economo whimsically termed this "the evolution of squishability."
Broader Implications Beyond the Ant Hill
The implications of this research extend far beyond entomology. The researchers see parallels in human history, such as in warfare, where smaller forces of heavily armoured knights were eventually overwhelmed by larger numbers of specialised, lighter troops like archers. They also reference Lanchester's Laws, mathematical principles from World War I describing how larger forces of weaker units can defeat smaller forces of stronger ones.
"The tradeoff between quantity and quality is all around," Matte reflected. "It's in the food you eat, the books you read... It was fascinating to retrace how ants handled it through their long evolution." The study suggests similar evolutionary paths may exist for other social insects like termites, though more research is needed.
Ultimately, by sacrificing individual protection, ants unlocked the formidable power of numbers. In doing so, they engineered some of the most successful and complex societies in the natural world, proving that in evolution, sometimes less really is more.
