banner by Matthew Stoss

Missing the Forest for the Trees

by Jesse Kaminsky

There is no question for which the answer remains as infuriatingly elusive as “What is life?”

I don’t mean to bring back unwanted flashbacks to biology lab, but few other questions in science remain so difficult to objectify. There are standards that have been widely agreed upon as requirements for an entity to be considered an “organism,” but for every law of life there are ambiguities that entice scholars to cast doubts into the definition. The most widely known example of this are viruses. Viruses follow the same generalized life cycle as other living things, including the ability to produce offspring, except that they require a host to do so. As such, it is widely disputed as to whether or not viruses are alive. While most say no, some say yes (myself included), and some say they are a shade of gray, neither animate nor inanimate. Viruses demonstrate that “life” is an altogether subjective term with interpretive guidelines organisms can follow, but may not.

Another intriguing edge case is the ant colony. It might seem silly to say an entire ant colony is a living thing. After all, ant colonies are simply collections of multiple organisms and cannot therefore be “alive” themselves. In fact, scientists have coined the term superorganism for such entities. While this term may seem to imply living behavior, it is open to debate as to whether a superorganism can truly be considered alive. Even if ant colonies don’t make intuitive sense as living things, they meet most of the widely agreed upon “definitions of life” (in considering each standard of life, as we are treating ant colonies as single organisms, the mention of ants will be reserved only for when it is absolutely necessary). Many would point out that if a being is composed of numerous subunits, each of which could be considered an individual organism, surely the whole is just a grouping, even if it behaves similar to other living things. A strong counterpoint to this view would be humans, or multicellular species in general.

Humans are not superorganisms (which usually implies some form of social interaction between subunits), but we are still composed of trillions of smaller living things, namely cells. In fact, just as our cells are divided into various types and classes, ants are also functionally divided into several castes that each play different roles such as foraging, defense, and larvae care. One might fallaciously point out that a colony, as a system, incorporates certainly inanimate components such as the hill itself (in the case of mound building colonies), as well as foreign organisms such as parasites and various symbiotic microbes that play important roles in the colony ecosystem. The human body contains similar components. One wouldn’t say hair is alive, but it is definitely a part of the human entity. Likewise, we all have diverse microbiomes of bacteria in our guts that play a vital role in digestion. An alternative view on the former argument is that since colonies often move from mound to mound, it is more similar to a hermit crab (if crabs built their shells) and so the mound needn’t be considered a part of the colony at all.

Another apparent difference between superorganisms and multicellular organisms is that while cells exist in conjunction with other cells and cannot survive on their own without the right laboratory conditions, ants are wholly independent animals. While this is anatomically true, ants have evolved extremely collaborative behavior. If only a small number of ants are placed together in a basic environment, they will simply wander in circles until they die. Even though an ant is a complete organism physiologically, if they are behaviorally not, what’s the difference between them and a human cell that requires a system to prosper and ultimately reproduce? Not only will individual ants not produce offspring, some ants will even sacrifice themselves for the good of the colony. In closing the nest at night, ants working on the exterior simply proceed to die once they can no longer get in. They do this to protect larvae that they did not create; as eusocial insects, a single ant (the queen) is responsible for the entire next brood.

That said, the question remains as to whether colonies reproduce. If a colony is defined simply as a collection of ants operating under the same central pheromone control and queen, then the answer is yes. When of a sufficient size, army colonies will split, producing a new colony that will then emigrate elsewhere, usually taking over a preexisting colony and even enslaving the resident population. This is reminiscent of a mitotic parasite. Other kinds of colonies will produce new queens that also emigrate elsewhere and begin a new colony. The queen could be considered a gamete that has been sent to merge with another of the opposite sex in the process of meiosis. Of course, the queen will be fertilized by a male ant and produce offspring through meiosis, but from a higher perspective the net effect is still one colony producing new ones.

So, colonies do reproduce, but that doesn’t necessarily mean they contain genetic material. This is by far the most difficult aspect of the discussion from the colony perspective. A collection of organisms would have to use some incredibly complex social “memory” to contain heritable information. As far as we can tell, in most colonies the offspring are simply based off the queen’s genetic identity. For this reason, the lack of genetic material at the superorganism level is the biggest counterpoint to the idea that a such an entity can be alive. Another example of this drawback would be the so called “Gaia Hypothesis” proposed in the 1970’s by James Lovelock and Lyn Margulis. In this theory, Lovelock and Margulis argue that the entire Earth is one huge living thing. As would be expected, the inability to undergo evolution due to the absence of genetic information at a planetary level, just as in colonies, is one of the biggest criticisms made by Toby Tyrrell, a professor of earth science at Southampton University.

Nevertheless, colonies do meet one more standard of life. Most biologists would insist that to be alive, an entity must interact with its environment in some way. Obviously ants interact with their environment (primarily the fascinating task of picking things up and putting things down), but colonies do too. If one looked from far enough above at a colony to see groups of ants but not individuals, it would look like a body with a number of arms reaching out to food sources and moving around amorphously to find new ones. Even more convincingly, the ants that make up those arms simply carry the food back to the main body of the colony, eating only what they must to stay alive. This means that food is being sought by the limbs of the colony and transported back to the main body, showing that colonies interact with their environment at a level beyond single ants. Colonies have also been shown to react to predation en masse. In removing a colony’s scouts (which in a natural setting would imply they were eaten), one study published in PLoS ONE in 2015 found that the response is an increased density of ants at the colony center and the retraction of its limbs. When they removed individuals from the center, the colony dispersed as a whole. The point is that in response to environmental stimuli, colonies act as a whole in organized style, just like a human would if under attack by a lion. Your cells would interact and produce a response intended to put as much distance between all of them (i.e. you) and the lion.

So are colonies alive? Unfortunately, there is no definitive answer (big surprise). Life is not yet understood nor defined well enough for there to be an objective answer. Regardless of their classification, many superorganisms are functionally comparable to organisms like you and I, raising some pretty meaningful questions regarding our ability to recognize life. In studying a system, how often do we miss the forest for the trees? For example, in exploring outer space or our own ocean, we may be too focused on the subunits of a larger superorganism to recognize the entity itself. Entities that meet every standard of life through the interaction of a number of subtly living components, or even components that seem inanimate, may be just waiting to be recognized.