The Remarkable Evolution of Mammals: Why They Transformed into Anteaters 12 Times After the Extinction of Dinosaurs

1. Introduction: Was "Ant-eating" Inevitable Rather Than an Exception?

In the savannas of South America, a giant anteater extends its long tongue into an anthill, while in the African night grasslands, an aardvark uses its keen sense of smell to locate termite nests. Meanwhile, in the eucalyptus forests of Australia, an echidna inserts its snout into the soil, and 10,000 kilometers away under the eucalyptus bark in Western Australia, a small numbat devours 20,000 termites. These creatures, despite differing regions and lineages, exhibit "astonishingly similar ecologies" and morphologies, which are not products of evolutionary chance but rather of "convergence." A new study reports that this adaptation occurred independently at least 12 times after the extinction of dinosaurs, posing new questions for evolutionary biology.IFLScience

2. Overview of the Study: A Massive Dataset Covering 4,099 Species

Associate Professor Philip Barden and his team at the New Jersey Institute of Technology (NJIT) integrated literature, stomach content analyses, and conservation reports from the past 100 years for nearly all 4,099 extant mammal species, constructing a large-scale dietary database. They then combined ancestral trait reconstruction with time-calibrated phylogenetic trees to statistically model dietary transitions. The results revealed not a single lineage but 12 independent events.Phys.org

3. Breakdown of the 12 Events: Covered Across the Three Major Mammalian Groups

The analysis revealed that the 12 origins are spread across monotremes (1 time), marsupials (3 times), and placental mammals (8 times). Particularly in placental mammals, insectivorous lineages are more prone to "jump," with transitions from carnivorous lineages being three times less frequent. Surprisingly, certain groups within carnivores, such as canids, ursids, and mustelids, account for about a quarter of all origins. Experts suggest that "the plasticity of dentition and jaw joints might be the key."Phys.org

4. The "One-way Ticket" of Diet: Why It Becomes a Dead End

The research team also confirmed the tendency that **"once you choose ants, there's no going back."** Characteristics such as elongated skulls like those of weevils, degenerated teeth, sticky tongues, and strong forelimbs are highly specialized traits that are difficult to repurpose for other prey, resulting in suppressed diversification of lineages. The only exception seems to be the genus Macroscelides, which apparently made a "U-turn" to omnivory during its evolutionary history, but this is an exception among exceptions.Phys.org

5. The Rise of Ants and Termites: Was the PETM the Decisive Factor?

Why did the "ant-eating boom" occur after the extinction of dinosaurs? The team reanalyzed insect fossil records and showed that the population and colony sizes of ants and termites exploded after the Paleocene-Eocene Thermal Maximum (PETM: about 55 million years ago). This was likely driven by the expansion of angiosperms and a hot, humid climate. The dramatic rise in insect biomass can be said to have "attracted" mammalian diets.Phys.org

6. Prehistoric "Ant Hunters": Fossil Examples Including Fruitafossor

Not only today's anteaters and aardvarks, but also the small mammal Fruitafossor from the Late Jurassic was found to be an ant specialist based on fossils. Although unrelated to extant groups, its strong forelimbs and degenerated teeth are good examples of "independent convergence." Such fossils are not included in the "12 times," but they tell of how often myrmecophagy has been repeated throughout evolutionary history.Wikipedia

7. Reactions on Social Media: "Evolution Is Really Cool"

After the research was published, social media was filled with a variety of voices, from admiration to jokes.

• Journalist David Wallace-Wells tweeted, "Converging on the same diet 12 times over 66 MY tells of the 'compelling force' of evolution."X (formerly Twitter)

• Handle name Ms. Iso Tope expressed excitement, saying, "Evolution is DOPE! I want it in textbooks."X (formerly Twitter)

• @Earth_Media_ posted with a touch of irony, "Let's see if the '13th anteater' will appear next, tracking it with global warming simulations."X (formerly Twitter)

• The official Phys.org account's tweet garnered 4,700 views and 5 retweets in 24 hours, showing high dissemination for a specialized news piece.X (formerly Twitter)

In Japanese-speaking regions, simple questions like "Aren't numbats cute?" and "Don't porcupines eat ants?" were also seen, and the technical term "myrmecophagy" temporarily trended.

8. Climate Change and Future "Potential Anteaters"

Insect colonies thrive in high temperatures. Currently, invasive fire ants are moving northward in the 30-degree north latitude zone, impacting ecosystems. Researchers warn that if colony-type insects increase, more mammals may adapt to ant-eating in the future. At the same time, specialization is closely tied to vulnerability, and as deforestation and pesticide-induced insect decline progress, species trapped in an "evolutionary dead end" face extinction risks.IFLSciencePhys.org

9. The Perspective of Ecosystem Services

Ant-eating mammals are not just "curiosities." They regulate vast insect biomass and act as "eco-engineers" by promoting seed dispersal and soil aeration. Particularly, their predation on termites may help reduce methane emissions, indirectly contributing to climate change mitigation.

10. Mechanisms of Convergent Evolution: Is a "Dead End" Really a Dead End?

Convergent evolution is the phenomenon where "similar environmental pressures lead to similar solutions," but while some lineages like Fruitafossor have gone extinct, others like the extant echidna have survived for 70 million years. The key factors are the "degree of specialization" and "environmental stability." The study focused on the tendency of ant-eating lineages to end as a single species, but the potential for survival may still be debated, hinging on genomic plasticity and behavioral flexibility.

11. Innovation in Research Methods: The "Metadata Revolution"

This achievement is also an example of how "meta-analysis × big data" has brought new insights into classical animal taxonomy. By integrating data across museums, conservation organizations, and citizen science platforms, previously overlooked patterns have emerged. The research team plans to expand the fossil database, including extinct mammals, to explore the possibility of a "13th time."Phys.org

12. Conclusion: "Seeing Evolution Beyond the Anthill"

Ants and termites are the "hidden giants" of the surface. Their behavior and sociality have influenced the evolution of soil, plants, and even mammals. This study has highlighted the grand causality of how small insects move large mammals. When we kick an anthill, we are witnessing a drama of evolution that has continued for 66 million years—doesn't that make each little insect at our feet look a bit different?