Opinion | In the ‘collective’ memory of 30 million ants

Human memories emerge from the way individual neurons interact, just like an ant colony's collective memory is created by behaviour of its members

Time, I suspect, for one more article about myrmecology. Given that we’re only days past Christmas, perhaps you think this has something to do with studying that mysterious substance called myrrh? Not at all: it has do with studying those mysterious animals called … ants. Yes, and you four regular readers of this column will recall that I have a weakness for ants and their always intriguing behaviour. So today, you get to read about ants and … hmm, I forget.

Anyway, in owning up to a weakness for ants, I am in distinctly exalted company. I refer to the brilliant Richard Feynman, who not only observed and experimented with ants all the time, he even wrote about them in his delightful autobiography, Surely You’re Joking Mr Feynman! Consider, for example, what he did when he found ants visiting the pantry in his home to feast on the food he had stored in there. The rest of us might pour a mug of water on them, or spray them with some toxic pesticide. But when it came to ants and to discouraging their pantry raids, Feynman was a touch more humane than that. He made himself many little paper strips, then folded each strip in the middle so it was L-shaped. He called these “ant ferries" because he planned to use them to pick up individual ants—and here in his own words is how he used these ferries:

“In preparation, I put a bit of sugar about 6 or 8 inches from their entry point into the (pantry), that they didn’t know about… (W)henever an ant returning (from the pantry) with food walked onto my little ferry, I’d carry him over and put him on the sugar. Any ant coming toward the larder that walked onto a ferry I also carried over to the sugar. Eventually, the ants found their way from the sugar to their hole, so this new trail was being doubly reinforced, while the old trail was being used less and less. I knew that after half an hour or so, the old trail would dry up, and in an hour, they were out of my larder. I didn’t wash the floor. I didn’t do anything, but ferry ants."

Think of what happened here. The ants had found a particular route that took them from their hole to food in Feynman’s pantry. In some sense—ah, I remember! — you might say they had created a sort of collective memory of this route. After all, even an ant that had never gone foraging in the pantry could simply follow this route to get there. Certainly, the path isn’t part of that particular ant’s memories— because it has never taken that path—but somehow it is embodied in the whole ant colony’s consciousness.

But along comes Feynman, with his paper ferries, disrupting that collective memory—“the old trail would dry up", he writes. At the same time, the ferries nudge the ants to mark out a new route—home to sugar and back—and thus create a new collective memory. For think of it: suppose you had a lazy ant that emerges only now, after Feynman’s experiment is over, from its colony. Where would it go for food? Straight to the sugar, clearly—whereas had she emerged an hour earlier, before Feynman began ferrying, she would have strolled straight into the pantry.

Put this another way: at least as far as memory goes, an individual ant is not acting like an individual entity, and in fact we shouldn’t think of the little fellows that way. It’s not that each of them remembers the path to food. Instead, each ant behaves more like an individual neuron in our brains. Each of those nerve cells has no particular memory of its own; but it’s in the way they behave collectively that we form and hold memories. Human memory emerges from the way our neurons interact; the memory of the ant colony, if we can comprehend such a thing, emerges from the way its inhabitants interact.

A recent article in Aeon (An ant colony has memories that its individual members don’t have, 11 December,) explores just this idea. Stanford University biologist Deborah Gordon writes there of ant nests in Finland that remain in the same place for decades, “occupied by many generations of (ant) colonies". Each such colony “remembers its trail system leading to the same trees, year after year, although no single ant does. … (W)hen the ants emerge (after hibernation) in spring, an older ant goes out with a young one along the older ant’s habitual trail. The older ant dies and the younger ant adopts that trail as its own, thus leading the colony to remember, or reproduce, the previous year’s trails."

From those thousands of small interactions, a colony’s memory is formed. Gordon showed this in other ways, too. Like Feynman with his ferries, she “perturbed" the ants—put obstacles in their way, or “created a disturbance" that they had to fight off. These perturbations affected only a small subset of the ants, but curiously enough, the behaviour of other ants also changed. Gordon explains:

“After just a few days repeating the experiment, the colonies continued to behave as they did while they were disturbed, even after the perturbations stopped. … No individual ant remembered anything but, in some sense, the colony did."

Fascinating, but there are still more facets to this idea of a collective memory. Now, while an individual ant lives for only a year, colonies exist for decades. Gordon found that younger colonies had more overwrought reactions to her disturbances than older ones did; much like human teenagers would be annoyed by irritations that human adults might take in their stride. The older colonies, she comments, “grow up to act more wisely than younger smaller ones, even though the older colony does not have older, wiser ants."

Collective wisdom and maturity: even more fascinating. But there are times when older may not necessarily equate to wiser—again, just as with humans.

Linepithema humile is an ant species native to Argentina, and thus they are popularly known as Argentine ants. Over time, they have been inadvertently introduced to many countries the world over—Japan, New Zealand, South Africa, the US and across Europe. A 2002 paper (Evolution of supercolonies: The Argentine ants of southern Europe, by Tatiana Giraud and two colleagues, published in Proceedings of the National Academy of Sciences,) reported something truly astonishing about the Argentine ant population in Europe: that they could in effect be divided into two “supercolonies", each spread across thousands of European kilometres. The larger of these, Giraud et al tell us, “effectively forms the largest cooperative unit ever recorded".

This is not to suggest that an entire continent is carpeted by two gigantic ant mounds. But consider what these researchers found. Ants of one supercolony, even if they come from widely separated nests, never are belligerent towards each other. They seem to recognize that they are somehow linked. But put ants from one supercolony together with ants from the other and both sets immediately turn aggressive. This is no mere exchanging of insults. The ants start attacking each other viciously, intent on slaughter.

Yet in both cases, these are ants of the same species.

It’s almost as if Europe has been partitioned into two teeming ant nations—call them Antia and Antistan—and these two are locked permanently into hostility and war. “War" is an apt word, really. In observing two hostile Argentine ant supercolonies in the southwestern US, researchers estimated that the fighting between them kills 30 million ants every year (Adventures Among Ants, Mark W. Moffett). In supercolonies that can contain a trillion ants each, 30 million is a vanishingly small fraction. But it still gives you an idea of the nature and scale—and ultimately, the futility—of the belligerence these ants exhibit.

What do we have here with these incredible supercolonies? First, these are gatherings of ants that have developed some collective idea of who belongs and who doesn’t. There’s that notion, again, of a collective consciousness or memory. Second, these are old, long-established colonies. Yet, if you imagine age brings wisdom like Gordon speculated about —in particular, the wisdom to question war and killing, to try to live in peace—well, these Argentine ant supercolonies haven’t found that particular collective wisdom. Just as plenty of mature human nations haven’t found it either.

Deborah Gordon ends her article thus: “Your memories are like an ant colony’s: no particular neuron remembers anything, although your brain does." Push the analogy further and you get something to ruminate on. As years turn into decades, individual citizens of belligerent nations naturally tend to forget the reasons for the hostility.

Although the nations remember. So the killing continues. Ruminate on that.

Once a computer scientist, Dilip D’Souza now lives in Mumbai and writes for his dinners. His Twitter handle is @DeathEndsFun