Our Inner Ape summary

Charles Darwin rejected the church’s view that god created man and man’s morality. In his groundbreaking work from 1859, On the Origin of Species, Darwin argued that all species, including humans, were actually beings that had evolved over the course of millennia. During this process, genetic variations that contributed to the preservation of the species continued developing, while those that didn’t, disappeared.

In his 1963 work On Aggression, Konrad Lorenz went on to augment this thought by arguing that evolution’s purpose for the individual was not to preserve one’s own species but to pass on one’s own genes. It would thus be evolutionarily beneficial for individuals to dominate others – and even to hurt and kill the members of one’s own species – if this helped their genes.

In the past, we called bonobos “pygmy chimpanzees.” Although they are the same size as chimpanzees, they are more delicate, their heads are smaller and they have long hair with a prominent middle part. They can walk upright and their voices are much higher than the chimpanzees’.

Bonobos have only been studied in the wild since the 1970s, but even before then people had noticed crucial differences between them and chimpanzees. For example, one circus went so far as to borrow a male bonobo in the hopes that it would breed more delicate offspring with the troupe’s female chimpanzees. But the progeny of this strange ape behaved so indecently (they had constant sex with each other in all possible combinations and positions) that they couldn’t be used for children’s shows.

For a long time, experts were reluctant to believe what field researchers were reporting about the bonobos: that even though female bonobos, like human females, are physically weaker than their male counterparts, the females are the dominant gender. Once, when de Waal publicly presented results on this subject, a German professor in the audience shouted out angrily, “What’s wrong with those males?”

The key is, female bonobos stick together, and thus as a group they can stand up to the males, who aren’t as socially cohesive. With chimpanzees, it’s the other way around. This difference might have to do with the variations in the two species’ habitats, which are separated by the Congo River: The bonobos live in the rainforest south of the river, whereas chimpanzees live in the far less lush north. Female chimpanzees searching for food in the forest are forced to split up, because the region is too barren for the entire group to find enough leaves and branches in one place. Thus, they are usually alone and carrying their young with them. Male chimpanzees, by contrast, hunt in groups on the steppes, and as a result they end up acquiring more food than the females.

At the end of the 1980s, Frans de Waal witnessed an interesting scene: just a few hours after the conclusion of a bloody fight between two chimpanzee males, the two gave each other a heartfelt hug. And the entire group watched them do it: a public reconciliation! This behavior puzzled de Waal. Why would the winner of a fight make peace with the loser if it didn’t benefit him directly?

The solution is simple: since male chimpanzees hunt in a group, they have to cooperate. There have to be clear hierarchies, and each member of the group has to recognize them.

The group status of a chimpanzee male determines his sex life: the more powerful he is, the more females he can have sex with, and the greater his chances of reproducing.

Chimpanzee females only bear one child per pregnancy – twins are very uncommon – and they breastfeed for four years, during which time they can’t get pregnant again. As a result, the males have an extremely small window of opportunity to get females pregnant, which also ups the competition among them. Only the genes of the males who win this competition will be passed on.

Physical differences in gender can help us draw conclusions about the development of our species. Gorilla males are three times as heavy as the females, weighing up to 300 kg (or 661 lbs) – and the alpha male is in absolute control. Chimpanzee males are only a few centimeters bigger than the females but, due to their muscles, weigh one and a half times more. Although male chimpanzees are dominant, their dominance isn’t as extreme as the gorillas’, whose females have hardly any power.

Things are different in the bonobo world. Males are only slightly larger and heavier than females. We can thus assume that the male ancestors of the bonobo were dominant, even though today the females are the ones in power. At some point, some relation dynamic must have been reversed, causing the males to become smaller. The males didn’t have to win any more fights in order to have sex, and so having bulging muscles no longer yielded evolutionary benefits.

Despite their size and breadth, male gorillas have extremely small testicles. But, since no other male gorilla dares to approach the boss’s lady friends, the boss needs very little sperm to impregnate the females of his harem. Simply put, his sperm has zero competition.

The testicles of a 70 kg (150 lb) chimpanzee are twice as big as those of a 200 kg (440 lb) gorilla. While the silverback is the clear ruler of the gorillas, the head of a chimpanzee group is more like the chairman of a ruling party. He has to grant his comrades some access to females, and the males in the lowest rungs of the pecking order will probably attempt to impregnate the females behind his back. His sperm might have priority over the others’, but there is a certain degree of competition, which is why he needs more sperm – and bigger testicles – than the gorilla.

Twenty years ago, it was observed for the first time how a lion killed all the cubs in a pack after taking power. Why was he so brutal in his first day on the job? The answer is simple: so the lionesses would be ready to mate with him more quickly. It could even be shown that the smell of the murdered cubs’ blood triggered the mothers’ ovulation. Since then, a similarly shocking behavior has been observed among bears, rats, dolphins and all primates – except for bonobos.

In these species, the interests of the female are up against those of the male. The genes of males that eliminate the offspring of their competitors and quickly father their own are the ones that prevail. The females, however, are also driven to protect their own genes, and the lives of their children – regardless of who the fathers are.

A sense of fairness was considered a purely human characteristic until Frans de Waal documented it among capuchin monkeys. His discovery was met with such incredulity that he had to repeat the experiment countless times. He sets it up by teaching two monkeys how to hand over pebbles to a scientist from their cage. As a reward for each successful pass, they both receive a slice of cucumber.

However, after twenty-five passes, one of them receives the usual slice of cucumber while the other unexpectedly gets a sweet grape – a more desirable reward. The monkey that gets a slice of cucumber cries out loudly, and in the next round he carefully checks whether there’s anything wrong with his pebble before handing it back. When he’s unfairly remunerated for his action yet again, he throws the slice of cucumber at the researcher and refuses to keep on playing, and eventually even throws pebbles at the researcher.

Many highly developed animals can understand the feelings of fellow members of their species and even those of related species. Take the striking example of the yawn. Like human beings, other animals capable of empathy – like monkeys, dolphins and horses – automatically yawn when they see others yawn. Some dogs even yawn when they hear a recording of their master yawning. Interestingly, people with autism (i.e., those who have difficulty understanding other people’s feelings) don’t “catch” other people’s yawns.

Primates, however, go beyond simply recognizing others’ feelings – they can also imagine how others feel, which is an even higher level of connecting with one another. In one experiment, researchers blindfolded a chimpanzee and hid some food from him while another chimpanzee watched. When the blindfold was removed, the scientists observed both chimps. It was clear from the behavior of the "watcher" that he did not expect his companion to also know about the secret stash.

All primates are hostile toward members of other groups. In the 1970s, renowned British ethologist Jane Goodall observed a behavior among chimpanzees in the wild that she termed murdering, as the chimps had clearly planned to attack with the intention of killing.

One night, patrolling chimpanzees snuck to the border of their own group’s territory, caught sight of a male from the enemy group, dragged him into the bushes and beat him to death. They didn’t fight the way they do with others from their group and instead treated the victim like prey. Over the course of a few months, they went about killing most of the other group’s males in the same way. After that, they raided the enemy territory, killed all the young, raped the females and took over the territory. Such “wars” are not uncommon among chimpanzees in the wild.

We humans naively believe that we make moral decisions based on rationality and of our own free will. If that were the case, moral decisions would have to be made in the cerebral cortex, but if you scan the human brain when it’s contemplating a moral dilemma, it’s primarily the deeper brain regions – the ones we have in common with other primates – that are active.

For example, the brain activities of various test subjects were scanned while they were told to imagine themselves in the following dilemmas:

Humans have two inner apes. The first is the “typical” competitive ape. Evolution rewards all animals that show aggressive competitive behavior and multiply. That’s why all primates, especially the males, have an inner ape urging them to conquer their competitors.

But, as group animals, primates have another inner ape: the collaborative ape. This ape has clear inherent social instincts, a sense of empathy, a desire for fairness and the impulse to help and comfort others. The collaborative ape developed later, empathy being a greater capacity.

Many social theories are based on a false idea of humanity. Communism, for example, assumes that competitive behavior can be overcome, that it disappears as soon as nobody is being exploited anymore. In light of evolutionary logic, this assumption appears rather questionable. In contrast, proponents of the free-market economy believe that people only act in their own interest, but these free-market economists are then flabbergasted at how irrationally and “stupidly” people behave in the end. Like other primates, humans have both a willingness to help others and sense of fairness: there are far more powers at work among primates than pure egoism.

Rationality makes it possible for us to see which behaviors are likely anchored in our genetic make-up. We can’t directly analyze the origins of our feelings, but when chimpanzees behave exactly the same way we do in comparable situations, the probability is high that we are observing an inherited behavioral pattern. This doesn’t mean that we can’t act any differently – it just means that our impulse to act a certain way will be extremely strong, and therefore we have to counter it equally as strongly if we want to change it. For example, rationality alone isn’t enough to offset our inbred xenophobia. We have to harness the empathy of our other more collaborative inner ape.

The main message in this book:

Morality is just as deeply anchored in our animal heritage as aggression and competitive behavior. The thing that makes us human isn’t the battle between “good” and “evil” but the ability to observe and describe it.