Digging Up Ants’ Evolutionary Origins

The lowly ant—they patter along the ground, are trodden underfoot, and generally survive on bits of detritus. But they’re an indisputable evolutionary triumph. They thrive in places high and low, north and south.

Despite how common ants are, evolutionary biologists have struggled to identify from where, exactly, the proto-ant first crawled forth. Was it from a tree limb, hoisted high above the ground? Maybe from beneath a leaf that had fallen to the forest floor? Or perhaps from the soil itself?

Ants' evolutionary origins have stumped scientists.

Recently, scientists have favored the idea that ants originated from a species living in leaf litter—the grandly titled “Dynastic Succession” hypothesis. It claims that ants first evolved in the detritus of tropical forests and then, over millions of years, marched from there up into the canopy and and down into the dirt.

But a new paper in PLoS One challenges that assertion, suggesting instead that ants evolved a few inches below the leaf litter, in the soil. Andrea Lucky, who was at the University of North Carolina when she conducted the research, led a team which tested with computer models the two prevailing hypotheses, Dynastic Succession and the “Out of the Ground” hypothesis, which says that ants evolved in the soil, not leaf litter.

The data that powered Lucky and her colleagues’ models were primarily phylogenetic, or information about ants’ evolutionary lineage. They also included details about each lines’ niche in the ecosystem. The team then ran the computer simulations to see which ancestral state—either litter living or soil dwelling—was statistically most likely.

Lucky and colleagues, writing in PLoS One:

Rather than finding support for the early rise of ants as surface-dwelling, we find evidence that early ants evolved underground and subsequently transitioned into leaf litter and forest canopies.

Discovering the origins of ants may seem esoteric, but learning more about them could help us understand how such a small insect ended up conquering the planet.

Discover what studying ants has taught us by watching "Lord of the Ants."