If I ask you about the origin of civilization, you may first think of different regions such as the Mesopotamian (the modern-day Iraq), Ancient Egypt, the Indus Valley (current northwest India and Pakistan) or China, which were the birthplace of the earliest human organization as a society. These are the regions in which 4000 or 5000 years ago, humans started developing complex social, political, and economic systems. Besides, it is the origin of human division of labor.
You guessed something like that, didn’t you? Not a bad attempt to guess the first civilization ever, except for the fact that you are completely wrong! What if I told you that there was a civilization that originated 30 million years ago in Eastern Africa (present-day Ethiopia, Kenya, Djibouti and Somalia)? That’s right! And you know what? This civilization was not human. Let me introduce you to naked mole rats!
Naked mole rats are these hairless, not too graceful rodents that have been inhabiting the East African underground for tens of millions of years and that you’ve probably only seen in pictures. They say beauty lies within. Certainly not within the earth! But researchers still love them because of their impressive physiology. First, they are the only existing cold-blooded mammals. Plus, they have a very low respiratory and metabolic rate, which makes them adapt to extremely low-oxygen conditions like the ones found underground. In addition, they are super-powerful immortal beings known for their insensitivity to certain types of painful stimuli and their great longevity. But the most interesting thing about these animals is that they live in a complex society in the same way as humans.
The phenomenon of living in a high level of organization is known as eusociality. What does it mean a high level of organization? Basically, that they cooperate between individuals in the offspring care, that they divide the labor, and that their colonies are constituted by overlapping generations of individuals (in the same way we live in families with grand-children, parents and grand-parents). Another way of seeing these colonies of eusocial animals is as a superorganism. We can imagine them not just as a group of individuals working together, but is instead a single organism in which the individual members are analogous to the cells in a body. They have specialized roles that they satisfy for the sake of the group, much like the cells in a multicellular body have specialized functions that contribute to the overall health and survival of the organism.
A crucial feature of eusocial species or superorganisms is to have good communication between its constituents. For this reason, to better understand how these organized societies form and succeed, it is very important to understand how their individuals interact. The work of some researchers such as Alison Barker focuses on that. Stay with us a little longer and we will tell you what language naked mole rats speak.
Alison Barker is an American neuroscientist. She currently has her own group at the Max Planck Institute for Brain Research in Frankfurt. She studied biochemistry in the US at Brown University. She became interested in the chemistry in the brain, which led her to start a PhD in neuroscience at University of California, San Francisco. In the middle of her PhD her supervisor moved to Munich and she joined him. At that stage she was interested in studying visual processing behaviors in zebrafish: how animals can perceive something about their world, how that gets integrated in the brain and how it ultimately leads to a behavioral output. Then from her postdoc she shifted gears completely and started to study auditory information processing in social contexts taking the naked mole-rats as a model.
Juan García Ruiz: When we think of social animals, the first thing that comes to mind is humans, ants and bees because those species divide their tasks and live in an organized society. Is this feature limited to those species or instead all the species have some extent of organization?
Alison Barker: When people think of social hierarchies in the animal kingdom the most common examples are bees or other insects that have a queen, workers and other individuals doing specific tasks. This was mainly thought to exist in invertebrates and there were some hypotheses about why that might be in terms of genetic fitness and the ability to support individuals that are highly related. But there was a fantastic discovery in the early 80s by Jennifer Jarvis: she found the first eusocial mammal. When I say eusocial I mean fitting three criteria that was first described in insects: reproductive division of labor, cooperative care of the young and existence of multiple overlap of generations. All three criteria are present in the naked mole rats. They show a very strict reproductive division of labor, which means that only a subset of individuals breed in the colony. The naked mole rats actually have a structure that is very similar to bees. They have a queen that is responsible for reproduction, the only breeding feemale, and there are generally one to three breeding males, depending on the size of the colony. The rest of the colony divides their work into very specialized tasks, like soldiers which defend the colonies and workers, which will forage for food. A subset of the workers also care for the young. And the older individuals stay in the colony, so different generations overlap within the same colony. To answer to your question, there are a lot of species that are incredibly social and cooperative, but this sort of high level cooperation and this very strict hierarchy is rare.
JGR: What are the main forms in which social animals can communicate?
AB: Any social interaction is a complicated process that depend on multiple channels that can be decoded and integrated. For the naked mole rats, we know that they rely a lot on olfaction, audition and touch. Like many subterranean rodents they are mostly blind, so we don’t include the vision in our studies.
JGR: How crucial is the high-level societal organization for a species that has evolved this way? Otherwise said, could a naked mole rat survive on its own?
AB: One of the reasons why I love this animal is that it is such a nice example of the power of evolution. They are very well adapted to their ecological niche. Their natural habitat is located in Ethiopia, Kenya and Somalia, in very dry lands along the equator, so very little grows there and the periods of the year in which they can forage and look for food are limited. One of the reasons why the naked mole rats do so well in these environments is because they share resources. Plus, naked mole rats are cold-blooded, so they cannot regulate their own body temperature. This makes a lot of sense if you think of where they live. The temperature doesn’t really change that much along the equator. So in one sense they have given up some features and have developed others to survive, like this highly cooperative organization. I guess the naked mole rats could survive on their own for a certain period of time, but I think without their colony they wouldn’t do very well.
JGR: What are the big unknowns in the field of eusociality?
AB: Some of the biggest questions are how eusociality evolved, and how it has been maintained. One of the most striking things about this is that whenever you belong to some social group you give up some of your own agency. For instance in a society we give up some personal freedoms for the benefits of being in a society. In the extreme case of the naked mole rats they give up their ability to reproduce. So one of the big unknowns is the understanding of this weighting, what are the brain circuits that allow us to cooperate and override the basic urge for self-preservation or reproduction.
JGR: You study social communication with naked mole rats. What makes this model so interesting to explore this trait?
AB: I decided to study the naked mole rats because in their case the eusociality is very extreme. In general, in science you always look for the greatest signal-to-noise ratio so that you can really pick the things that stand out. Biology is messy and there are many factors that cannot be controlled, so if the behavior is very robust, that is a very nice place to start. The other reason why I chose the naked mole rats is because they are very easy to have in the lab, so then you can start adapting technology used in other rodents to better study neural circuits or molecular mechanisms.
JGR: What are the main questions your team is trying to elucidate?
AB: We focus on a specific type of communication. We are very interested in how vocalizations help social groups organize and how they enforce social bonds. We want to understand how these social signals are encoded and decoded. When an animal produces a social sound, another animal in the group has to detect it, process it and determine its meaning to generate its own behavior. There are many steps, and we want to better understand how it takes place in the brain. Naked mole rats are the perfect model to study this because besides being very cooperative, they are also highly vocal. They make at least 25 different vocalizations, and they can use these diverse sounds in specific social contexts. We know for example that there is a specific type of vocalization which is like a greeting call and is called the soft chirp. When two individuals encounter one another they emit this sound reciprocally. This provides multiple levels of information, such as the individual identity, or which social group they belong to. You can think of it in the way humans use dialects or accents: with a single vocalization you can get a lot of information about the other person. We are trying to focus on this and then move into the brain. We are also interested in how the social dynamics of the colony can change their vocal dialects and how it develops: how do young animals learn when they are born which dialect to use in each social context.
JGR: Can naked mole rats use these 25 vocalizations in a flexible way, for instance by combining them to create more complex meanings? Or do they use them in a more stimulus - response way?
AB: We are trying to figure that out. Vocalizations are very stereotyped responses in a lot of animals. Of course in humans it’s something extremely flexible. I think naked mole rats are in the middle. There is some kind of plasticity in their calls. But we are just scratching the surface. We have looked at this one vocalization type, and now we are trying to figure out what is going on with the other 24.
JGR: What are the main approaches you use to study social communication in naked mole rats?
AB: We have created interconnected tunnels made of Plexiglas, so we can see through them and observe how they behave in an environment that mimics their natural one. We are developing a system to see where each mole rat is and what other mole rats they talk to at each time. Then we analyze these vocal exchanges. So right now we are doing a lot of eavesdropping, and once we get some information about individuals and their social networks, we will go beyond. For instance, we can do targeted playbacks, or put a naked mole rat alone with a speaker so that we can control what we play to the animal and see how it responds.
JGR: What are the main discoveries that your team made?
AB: An important finding that we made when I was a postdoc working at the Max Delbrück Center for Molecular Medicine in Berlin is related to the soft chirp, a type of vocalization I mentioned before. We found out that this type of vocalization provides information about the individual naked mole rats identity and about which colony they are from. We could test this and we showed that naked mole rats hearing a soft chirp from their own colony would preferentially respond to that rather than to a soft chirp from another colony or an artificial sound, which suggests that they can recognize the general features of the colony in these vocalizations.
Another interesting finding is that these dialogues can be learnt early in life. So if you move a young naked mole rat to another colony, they will learn the dialect of the adoptive colony. If this was completely genetic, we would predict that regardless of where the animals were raised, they would speak the birth dialect. But that was not the case. Something quite interesting we discovered about those dialects is that they seem to be dependent on the presence of the queen of the colony. We had a colony in which the queen was lost in several overthrow situations. So there were periods in which there was no queen in the colony and we could see that the dialects got really messy and fell apart, and when there was a new queen the vocalizations became clear again. This means that the social dynamics of these animals are really important.
JGR: Do you share the opinion that research is today a challenging career choice?
AB: Research has always been complicated I would say. It is difficult to quantify that appropriately. But I think that one thing that is really powerful is the open-data initiatives we have today. Diversity in science is very important, and this first requires access. Having access to papers or to code is very important and I think that’s really moving science forward.
JGR: Do you have a book recommendation?
AB: One book that I think all scientists should read is Mary Shelley’s Frankenstein. This is not strictly scientific but it speaks to scientific ethics. Briefly, Frankenstein was a doctor that created a creature. He was so concerned about reanimating dead matter that he didn’t think about the consequences: what is the meaning? What are my responsibilities? And after he did it, he just let this creature run free and took no responsibility. Obviously that ended poorly for him. I read that when I was sixteen years old and it made a deep impression on me. As scientists we can do things that nobody did before, but we should always think of the consequences of our actions.
JGR: What can humans learn from other social species?
AB: Humans sometimes live with blinders on and have this very narrow view of things. Certainly from naked mole rats we can learn about cooperation and about resources sharing. One of the things that is most interesting when studying a rodent like the naked mole rats is to think about how we think of communication and how it can take on many different forms. It has been like an eye-opener. It made me rethink about the interactions we have as humans, what does it mean to communicate, or how do we structure language. Plus, studying naked mole rats is also powerful because it gets you to see something done in a different way, so it puts things in perspective.