Young ants build faster: what ant colonies can teach us about collective aging
Not all ant colonies build the same way. New experiments show that a colony's age structure -- how many young versus old workers it contains -- determines how quickly and how effectively the nest gets excavated. And that turns out to have a striking parallel with biological aging.
In the biology of social insects, the nest is more than a home: it is the physical structure of the superorganism, comparable to a skeleton. It grows with the colony, repairs itself after damage, and its architecture reflects the community's life history. But exactly how that construction process is regulated -- and in particular what role the age of individual workers plays -- has until now been poorly understood.
Researchers publishing in eLife report experiments with colonies of the ant Camponotus fellah. They compared two types of groups: young colonies that had grown organically from a single mated queen, and experimental groups in which the age of every worker was precisely known. What they found: equal numbers of ants do not dig equally. Young workers excavate significantly more, and faster, than old ones, even when the colonies are identical in size. Demography -- the age distribution within the group -- determines the colony's overall construction capacity.
The superorganism ages too
This might sound like an entomological curiosity, but it touches on a fundamental question in aging biology: does a colony grow old as a system, just as an individual animal does? The answer appears to be yes. As workers age, their individual contribution to collective tasks declines -- not in a straight line, but in a way that affects the entire colony. A colony made up mainly of old workers is considerably less capable than an equally large colony of young ones, even when the queen is still fertile.
The implications are interesting for both evolutionary biology and aging research. In ants, there is a direct link between the group's age composition and its collective performance. Something comparable is visible at the population level in humans: aging societies face a shifting ratio of working to non-working members, along with a decline in certain forms of physical productive capacity. That is obviously far more complex than an ant colony, but the underlying biology of aging as a property of systems is comparable.
Recovery after disaster: age matters there too
A second finding from the study concerns recovery after a catastrophe -- in this case, the deliberate destruction of an existing nest. Younger colonies recovered faster and rebuilt more efficiently than older colonies with comparable numbers of workers. The capacity for recovery also turns out to be shaped by demography. This calls to mind the literature on wound healing in animals and humans: there too, young individuals recover faster and more effectively than old ones, partly because cellular systems that become less responsive with age are still firing on all cylinders.
Whether ant colonies offer a direct translation to human aging questions is debatable. But as a model for collective biology and the effects of demographic aging at the systems level, they are unusually accessible and revealing.