Ants Provide a New Perspective on Healthy Longevity for Humans

Abstract：Ants, as eusocial insects, exhibit unique social structures that enhance their success and longevity. In ant colonies, sterile worker ants prioritize supporting queens and siblings over reproduction due to their genetic makeup, maximizing the propagation of shared DNA. Remarkably, when queens die, workers can transition into reproductive roles, gaining both extended lifespans and enhanced fertility. A 2022 study revealed that this transition is driven by insulin signaling, which boosts metabolism for reproduction while a protein, ImpL2, mitigates its lifespan-reducing effects. This decoupling of metabolism and aging offers insights into human health, suggesting potential strategies for achieving healthy longevity.

There are over 10,000 species of ants on Earth today, classified as members of the insect order Hymenoptera and the family Formicidae. Ants inhabit vast areas except for the polar regions, with ancestors tracing back to the Cretaceous period over 100 million years ago. Despite their diminutive size, ants are among the most "successful" species on Earth. A testament to this is their collective biomass, which accounts for an estimated 15%-25% of the total weight of terrestrial animals, despite each individual ant weighing only a few milligrams.

The key to their success lies in their unique social structure. Nearly all ants are eusocial animals, exhibiting highly organized social behaviors. These animals live in multi-generational colonies, cooperatively raising offspring, maintaining their nests, foraging for food, and defending against threats. However, the defining characteristic of eusocial animals is the division of reproductive roles among females.

For most living organisms, reproduction is the fundamental mission for survival and the cornerstone of 4 billion years of evolution. However, in eusocial species like ants, even reproduction is meticulously divided. Ant colonies generally consist of three roles: long-lived, reproduction-focused queens; short-lived, labor-oriented workers; and similarly short-lived males tasked with mating. While queens possess prolific reproductive capabilities, the majority of their offspring—the workers—are entirely sterile. Workers dedicate their lives to tasks like caring for the queen, foraging, and nest building [1]. Beyond ants, other eusocial insects like bees and termites exhibit similar structures, and findings from these species are often referenced interchangeably in related studies.

Evolutionary Puzzle of Eusociality

The phenomenon of eusociality puzzled Charles Darwin, the father of evolutionary theory. In On the Origin of Species, Darwin wrote that sterile female insects seemed to pose a fatal challenge to his theory, as their existence appeared to contradict the principles of reproduction, competition, and selection fundamental to evolution. Darwin proposed a collectivist explanation: if the presence of sterile females benefits the colony, this trait can be preserved. However, this explanation was at odds with his emphasis on the individual organism as the basic unit of evolution.

Modern biology has since resolved this paradox. If reproduction is viewed as the replication and dissemination of genetic material, the puzzle becomes clear. In most sexually reproducing organisms, offspring inherit 50% of their genetic material from each parent. However, in ant colonies, a unique mechanism ensures that worker ants share 75% of their genetic material due to their haplodiploid sex determination system. This makes caring for the queen and assisting in the reproduction of siblings a more efficient way for workers to propagate their genes than reproducing independently.

Specifically, worker ants inherit 50% of their DNA from their queen and the entirety of their DNA from their haploid father, resulting in a 75% genetic similarity among workers. This genetic framework incentivizes workers to forego reproduction and focus on supporting the queen, ensuring the colony's success.

Longevity and Reproductive Ability

Ant colonies have a fail-safe mechanism for replacing queens when one dies. Worker ants can partially develop reproductive organs and become "gamergates," a transitional state between worker and queen. These gamergates can sustain the colony's reproductive needs, and some may even compete to become the new queen.

This remarkable ability to switch roles hints at a biological "switch" that could extend lifespan and enhance fertility. Unlike most species, where increased reproduction often comes at the cost of reduced lifespan, ants achieve both simultaneously. This phenomenon is of great interest for understanding how humans might achieve healthy longevity.

Insulin Signaling and a New Mechanism

A 2022 study published in Science explored this phenomenon in detail [6]. Researchers at New York University, led by Danny Reinberg, discovered that changes in insulin signaling are key to the enhanced lifespan and fertility observed in gamergates. Using the ant species Harpegnathos saltator, the team found that worker ants transitioning to gamergates experienced a dramatic lifespan extension from 200 to over 1,100 days, alongside significant ovarian development.

RNA sequencing revealed that insulin signaling pathways in gamergates’ brains were markedly upregulated, driving accelerated metabolism and increased fat synthesis for egg production. However, the study also uncovered a unique regulatory mechanism: a protein called ImpL2 acted as a "brake" on insulin signaling, selectively mitigating its negative effects on lifespan.

This discovery provides a fascinating analogy: much like installing a bypass pipe to prevent food absorption while indulging in a feast, ants utilize ImpL2 to decouple the benefits of increased metabolism for reproduction from its typical lifespan-reducing consequences. This mechanism could offer valuable insights for developing strategies to extend human lifespan without compromising health.

Implications for Human Longevity

The study highlights how ants maintain both high reproductive output and extended lifespans, providing a novel framework for studying healthy aging. By understanding the balance of insulin signaling pathways and their regulation, researchers may uncover therapeutic approaches that enhance human health and longevity.

Ultimately, the biology of ants offers a compelling model for unlocking the secrets of living longer and healthier lives.