In search of ant ancestors.

Ants are arguably the greatest success story in the history of terrestrial metazoa. On average, ants monopolize 15–20% of the terrestrial animal biomass, and in tropical regions where ants are especially abundant, they monopolize 25% or more. But ants did not always run the world. They do not appear in the fossil record until the mid-Cretaceous, and for more than the first half of their history—a period spanning 60 to 80 million years—ants occupied a relatively modest position in the terrestrial biosphere. To understand the factors, both ecological and historical, that contributed to the rise of the ants, we require a clearer picture of the stepwise evolution of the major ant lineages. Now, Grimaldi and Agosti (1) report in a recent issue of PNAS the remarkable discovery of a worker ant, preserved in amber for over 90 million years, that is clearly assignable to a modern ant subfamily that contains many familiar extant species, including carpenter ants. Combined with other paleontological and phylogenetic information, this unexpected fossil strongly indicates that the diversification of many ant subfamilies occurred earlier and more rapidly than previously suspected.

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