Norbert Sachser in conversation

On humans and guinea pigs

Every human is unique. There are large and small, dark skinned and light skinned people, there are team players and loners, gentle and aggressive. And between all theses extremes there are countless nuances of humanity. But what does that look like in animals? Aren't they all the same within a species? A Dolphin is a dolphin, and a tit is a tit? Not at all, says behavioral biologist Norbert Sachser.

Professor Sachser, it would seem difficult to apply the concept of normality to humans because hardly anybody really embodies a statistical median. What’s the situation in the animal kingdom?
Today personality has become one of the key focuses of research into animal behavior. In the old days we used to say “Those are mallards, that’s a teal and then there are wood ducks.” And now we tend to describe how the ducks behave. We’ve been able to identify something typical for each of the species. But over time we saw that not all the ducks in a species are “in a row,” that there are no normal types. Instead there are lots of individuals. There are different personalities in the animal world, and not only among chimpanzees, dolphins and dogs. We can see individual characteristics among great tits and even leaf beetles. As a result, the emphasis of research has shifted significantly: there is far less interest in the median, i.e. in how a specific animal population behaves. We want to understand the variations from the norm. Denying “normality” as what the majority does is not a tenable biological approach.

That means that the variation of certain behavior can also be normal?
Yes, there are good examples of this, like the peppered moth. That’s a gray and white speckled moth that is found on the trunks of birch trees – where it sits perfectly camouflaged against the bark. In 1849 a different incarnation of peppered moth was observed near Manchester, England: one that was completely black. This deviation from the norm proved a sensation – albeit only for a brief period. Because, before 50 years had elapsed, almost the entire population looked the same, and there were hardly any gray and white speckled specimens left. What had happened? The Industrial Revolution in England. Because there were no environmental protections, all of the tree trunks were blackened with soot. The black mutant then had a huge advantage because it was camouflaged far better and predators could not spot it. This meant that it could breed more successfully. So within a few generations, the norm in this population of peppered moths had been replaced, and the vast majority were black morphs. Today, thanks to the improved air quality, birch trees once again look as they should, so once again the gray and white speckled morphs are seen most frequently. To sum things up: it’s risky to describe something as normal or abnormal on the grounds that one type is common and another rare. In a very short period of time – just a few generations – the exception can have become the rule, and vice-versa.

And the same holds true of humankind?
Society today is in severe upheaval. As individuals we might not always notice that, but it’s happening all around us. It’s all but impossible to predict how our world will look in 10, 15 or 20 years. And for this reason, it’s also difficult to know who will be able to solve the problems society faces in the future. In other words, our societies need to contain as diverse a range of people as possible. Only time will tell which individuals are particularly well suited to coping with the coming challenges. Pinning our hopes on one social type, defining this as normal and fostering it – that would be a catastrophe.

Norbert Sachser, a professor at the University of Münster, is regarded as the pioneer of German behavioral biology. His book Der Mensch im Tier (“The Human Animal”) was published in 2018. (Image: Willi Weber)
Evolution follows revolution. During the first decades of the Industrial Age, the peppered moth was typically black. Today it has regained its original speckled coloring. (Image: Shutterstock)
A guinea pig can resolve a conflict simply with a withering stare. (Image: Shutterstock)

Taking a proactive approach – is that skill the preserve of humans only?
That’s an area where we can identify a significant difference between animals and humans. Even the most advanced animals can only consciously plan ahead for a few days. In this context people often reference squirrels that collect nuts for the upcoming winter. But these are purely instinctive reflexes that are programmed into their genes. No squirrel sits around in the summer and suddenly thinks, “It’s going to start getting chilly in about six months, so I’d better start gathering and stashing some supplies.” This course of action entails no real cognitive processes.

But animals do have the ability to distinguish between normality and abnormality, don’t they?
When we human beings define normality, it’s a cognitive act. To do that, we have to put ourselves in others’ shoes, we need to be able to reflect on ourselves and the world around us. Which other creature possesses similar skills? Not a single one can compare with a human in this respect. There are, however, animals that can recognize themselves in a mirror, something beyond the power of one-year-old babies. A few can even view the world through the eyes of other animals, as though empathizing with them, and adapt their behavior accordingly. We’re talking here about dolphins, chimpanzees, the great apes, elephants and – interestingly – some species from the crow family. However, these abilities are not sufficient to give them reflective faculties, the ability to consider issues, and therefore to cognitively identify something as normal or abnormal. On the other hand, we often see animals reacting very aggressively to things that are different, without that being a product of cognitive skills.

Sometimes animals reject nonconformity ...
Yes. In a group of animals – chimpanzees, dogs or whatever – members of the group behaving differently are often subject to aggression. But that certainly doesn’t mean that this type of behavior is normal. That would be a dangerous conclusion to draw and we have no proof of that. In fact, there is more evidence to the contrary. We have observed that when two males from different large colonies of guinea pigs meet for the first time, they only eye each other up. They don’t feel the need to fight or threaten each other; their stress hormones aren’t elevated and they find ways of accommodating one another. And that has nothing to do with the fact that they are pets and have been bred to interact that way. For instance, if a male raised with a single female subsequently encounters an unknown male, it will display considerable aggression and increased levels of stress hormones. During adolescence, while patterns of social behavior are still being absorbed, these youthful guinea pigs have had no interaction with older, dominant males. As a result, the only way they know to respond is to threaten and attack a rival. By contrast, once guinea pigs have learned how to behave through previous interactions with older males, they are able to re-enact it for the rest of their lives. They retain the ability to co-exist with any unknown male that they subsequently meet.

So animals’ aggressive behavior towards outsiders is not a product of pure instinct. Rather, it is conditioned by the social environment in which they grow up and the rules they have learned during a particular phase of their lives. From a human perspective, we rightly condone people who can resolve confrontations peacefully and don’t display stress-related behavior when encountering unknown others. But from a biological perspective, both of these modes of behavior make good sense: if animals live in large colonies, it is obviously helpful to be capable of getting on with, and successfully integrating into, their social communities; after all, they will need to wait until they have moved up the pecking order. They become sexually mature within two or three months, but they only become alpha males or females after seven or eight months. Until then they are dovish, and that peaceful behavior allows them to mature, rise through the ranks, and then reproduce. So placidity is a benefit inside large social communities. However, if a male guinea pig lives with just a single female, it only breeds with that female. From an evolutionary perspective such a male would be expected to ward off a male intruder, so that it can continue handing down its own genes. Biologically speaking, aggression towards an outsider is the most sensible reaction in such a situation. But in a different situation, refraining from aggression might make more sense.

The lioness is the poor relation in the pride. (Image: Shutterstock)
When feeding the edglings, the male great tit combines the roles of biological and foster father. (Image: Shutterstock)

Anger is a behavior that we disapprove of in society, and jealousy too is stigmatized. As they are very natural responses, should we not be more accepting of them in humans?
We need to be careful not to draw the wrong naturalistic conclusions here. Take the example of infanticide in lions. Lions live in harems. There are frequently two males at the top living with several females. The males are replaced every two to three years. And what’s the first thing their successors do? They kill the cubs that have yet to be weaned. In the past this has been interpreted as a form of pathological behavior, as something sick and abnormal. Today we know that, viewed from the perspective of evolutionary biology, these males are acting absolutely sensibly. If males take over a harem, their goal is to hand down their own genes to the next generation as efficiently as possible. As long as the females in a pride are still lactating, they do not ovulate and therefore cannot become pregnant. If the males kill the cubs, the females soon start ovulating again, and the males can reproduce and pass on their genes. Today we know that this behavior is far from unique to lions; it is exhibited by numerous other species as well. So we could be saying that it is normal in the natural world. Which is certainly not to say that humankind should emulate it. We can’t simply adopt those animal behaviors that suit us and ignore everything else.

When I observe a pride of lions, I ask myself which one – the male or female – is the poor relation. What do scientists know about stress levels within the social grouping?
We observe so-called dominance hierarchies among almost all animals that form groups. Now, it would be easy to assume that being the alpha is great and being subordinate worse. But it isn’t that simple. Studies measuring the concentrations of stress hormones in the natural world have shown that alpha males are far from being the least stressed animals. They may be the ones that pass on their genes most efficiently, but they are also the ones that suffer most frequently from stress-related disorders, that develop cardiovascular problems such as high blood pressure and arteriosclerosis. Dominance is too strenuous to sustain for long periods. Yet here too animal and human communities differ: the main aim for animals is not to reduce stress levels and live as long as possible. Rather, their primary goal is to breed as successfully as possible. And if that demands an abundance of stress, then so be it. If they can achieve it by waging war – like chimpanzees – then they are up for it. And if they can breed most efficiently by cooperating, then all the better. The strategies pursued might differ but the objective is always the same: to pass on their own genes. No animal is “wired” to preserve its own species.

So regardless of where they are in the hierarchy – alpha, omega or somewhere in between – males experience lots of stress.
In many cases, yes. And frequently they benefit from it. But we mustn’t forget the females. What happens to them? In the lion hierarchy, they get dealt the worse hand. Sometimes they fight with males, but they are physically much weaker. Some females try to leave the pride with their young, but then their prospects of survival are slim. This shows that males and females often have competing interests. And in recent years, in very general terms, we have seen that females in the animal kingdom are far from passive bystanders that simply watch which male prevails in fights before mating with the winner. On the contrary, they are very proactive and, just like males, seek to hand down their genes to the next generation as efficiently as possible.

(Image: Shutterstock)

So this behavior is common to all types of animals?
Yes, for decades the behavior of songbirds was seen as the supreme example of monogamy and loyalty. Then, as is often the case in science, a revolutionary new technology became available: paternity tests using DNA fingerprinting. This indicated that, among blue tits and great tits for example, over 80 percent of the edglings in nests were not fathered by the female’s partner, i.e. the male that was feeding them. Initially researchers assumed that the males were being unfaithful so as to maximize their fitness. More thorough observations, however, reveal that the females are the ones that take the initiative. What’s happening here? The standard hypothesis runs as follows: usually the males arrive first and lay claim to a territory; only then do the females appear. And what does a female do if given a choice? Needless to say, it selects the best territory and best male. In that way it also gains access to the best resources and the best genes. However, the majority of females never encounter this situation because most territories already contain females when they arrive. So they have to content themselves with inferior territories and inferior males. They can, however, get the superior quality genes from the other males. And that, evidently, is exactly what they do. So it isn’t the case that a male bird meets a female bird and they then live ‚happily ever after.‘ Instead, predictable conflicts arise between the genders with the female typically deciding how it reproduces. Not so long ago scientists saw this very differently.

Now, it would be interesting to know if a male great tit knows that it is not the biological father of most of its edglings.
That’s a fascinating question that has actually been researched. Somehow the males must realize this: it has been proven that the more offspring from other males is in its nest, the less food the acting fathers provide. In short, they put less effort into it. However, nobody knows how the males deduce the parentage of the chicks.

In your book you state that the percentage of monogamous species is very small...
Approximately five percent of mammals are monogamous. In their defense I would add that cross-fertilization among monogamous mammals exists, but it is relatively rare. By contrast, almost 90 percent of bird species are monogamous but cross-fertilization is exceptionally common.

So the notion that lots of animals are monogamous is little more than a human attribution. And animals are in no way “uncorrupted human beings”?
Most definitely not. There are lots of examples of animals cooperating, supporting each other, consoling each other, and making peace amongst themselves. We have learned a great deal about such phenomena in recent decades. At the same time we can also observe how they threaten each other, wage wars, rape and kill. Animals are opportunistic. They will do anything to pass on their genes. And in this respect they are significantly different to people: animals cannot escape their genetically programmed egotism. Not the dolphins, not even the chimpanzees. But I haven’t completely abandoned the hope that we humans – at least in theory – will determine our actions based on other principles. We have laws, we can aspire to specific ambitions, we can adapt our ethics. That means that, as a society, we ought to be able to engage in very different types of solidarity, cooperation and responsibility than those available to animals.

In other words, leopards may not be able to change their spots but humans can. Is it possible to apply any of your investigative methods to our everyday lives? For example, you write that you often perform a kind of saliva test on animals to determine their cortisol levels; secreting cortisol is a symptom of stress. Wouldn’t it be good if people could carry around portable tests to measure how stressful we find different situations?
That has already become a key area of research in psychology. And there are comparable studies that have been carried out in parallel on humans and animals. When in large groups, guinea pigs don’t move around arbitrarily; they have longstanding partners and favorites. Let’s characterize all of the other guinea pigs in the group as “known,” and those that have never seen each other before are “unknown.” If you remove a single male from the group and isolate it in a new enclosure, it displays acute stress. Its cortisol level suddenly jumps. If you add an unknown female, the increase in cortisol is replicated, as it is with a known female. However, if you add the male guinea pig’s longstanding female partner instead, the stress level hardly increases at all. Research into humans produces similar results. For example, people in a laboratory were given mathematical assignments such as the following: “Starting at 1017, keep subtracting 23 until you reach zero. If you make a mistake, you have to start over – the last candidate did it in 45 seconds.” Challenges like this cause stress hormones to soar. However, if the male subjects’ spouses or partners are allowed to watch, the men respond exactly as you would expect: they exude less stress and perform better when the spouse or longstanding partner is nearby. Fascinatingly, the exact opposite is true of women. If their male partners are present, the women’s stress hormone levels climb sharply and their performance deteriorates. This again shows the great similarities between humans and animals. Having a good long-term partner is the best antidote to stress in difficult situations. You get exactly the same results in humans as in guinea pigs and many other species which have also been studied. The following conclusion can be drawn for all mammals, including humans. Friendship, longstanding partners, and integration in a social network are all therapeutic. They promote a sense of well-being and good health, and protect against stress.

How would you describe the philosophical core of your research? Is it a plea for diversity, i.e. for allowing variety in a given spectrum without immediately passing judgment?
Yes, without a doubt. But the aim is not for us all to be as diverse as possible and do anything we want. The moment I encroach upon other people’s freedoms, ignore the very pillars of our legal system, or start saying “I don’t care what happens to the planet,” my position ceases to be acceptable. In the big picture, however, we should be fostering diversity in our society and practicing more tolerance. Society will need diversity if it wants to master the problems facing us in the future. Of that I am quite certain.


Frank Haas is Head of brand strategy and communication at Gebrüder Weiss and editor-in-chief of Atlas.

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