Early Ants’ Society: New Fossil Clues to Ancient Sociality?

Recent findings published in Science Advances on June 14 reveal intriguing insights into the social lives of early ants preserved in 100-million-year-old amber. These discoveries suggest that even at their earliest (so ancient) stages, ants exhibited sensory adaptations indicative of complex social behaviors similar to their modern counterparts.

Today, all ants are known for their advanced societies characterized by communal living, cooperative parenting, and specialized divisions of labor within large groups. This social structure stands in stark contrast to ants’ solitary wasp ancestors, raising questions about when and how their social lifestyles evolved. Fossil evidence of early ants found in groups hints at the emergence of social behavior as early as the Early Cretaceous Period. However, the extent to which these ancient ants communicated chemically within colonies, as opposed to merely sharing habitats, remains a topic of ongoing research.

Ryo Taniguchi, a paleontologist at Hokkaido University in Sapporo, Japan, along with colleagues, conducted an examination of fossilized ants from one of the oldest known ant species, Gerontoformica gracilis. These ancient specimens, found preserved in amber in northern Myanmar and currently housed at the American Museum of Natural History in New York City, provided insights into the early social behaviors of ants. Taniguchi’s team focused their study on the ants’ antennae, which serve as critical organs for communication among nestmates.

Using an innovative microscopy technique designed to capture multiple angles of the fossil antennae, the researchers studied the sensilla—small sensory projections crucial for detecting environmental cues. By comparing the sensilla of G. gracilis with those of six modern ant species, they discovered two types of sensilla unique to ants. These specialized organs play key roles in identifying nestmates and detecting alarm pheromones, which signal danger to the colony. Such sensory adaptations are pivotal for ants to live cooperatively and defend their colonies collectively.

While many present-day ant species form massive colonies numbering from thousands to millions of individuals, the fossil evidence suggests that early ants likely lived in much smaller colonies comprising only a few dozen nestmates. Despite their modest group sizes, Taniguchi suggests that these early ants already exhibited a sophisticated social structure. This finding challenges previous assumptions about the timeline of ant social evolution, suggesting that their advanced social behaviors emerged tens of millions of years before they became ubiquitous ecological contributors worldwide.

1. ^{ONLINE NEWS} Buehler, J. (2024, June 14). Early ants may have had complex social lives, fossil data suggests. Science News. [Science News]
2. ^JOURNAL Taniguchi, R., Grimaldi, D. A., Watanabe, H., & Iba, Y. (2024). Sensory evidence for complex communication and advanced sociality in early ants. Science Advances, 10(24). [Science Advances]

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