The embrace mentioned in the title of this superb book was between two primates in old age. One of them was an 80-year-old Dutch biologist, Jan van Hooff, and the other Mama, a 59-year-old chimp, one of the oldest ever in captivity and, for much of her life, a famous matriarch among the chimpanzees in Burgers’ Zoo, Arnhem.

The YouTube footage of the moment is worth seeking out. It depicts an emaciated ape, close to death. Lying comatose in a foetal posture, she then recognises her long-absent human friend and instantly her arms open and an enormous grin blossoms on her weary face. She proceeds to stroke the cheeks and hair of her companion, finally drawing him closer, left hand wrapped about him as she drums her fingers gently on his crown. Many people who watch it admit to being moved to tears by the tenderness of the scene.

In a sense this book is a literary validation of that audience response. One could even say that the author’s whole career has been an attempt to prove that the emotions manifest in the tableau of Mama and Van Hooff were as genuine as they seemed and, more important, as meaningful for both parties. De Waal’s work has thus entailed a degree of intellectual struggle, because, while few have any problem with human emotions, the very concept of animals having them too – including love, a sense of fairness, altruism, loss, jealousy, envy and resentment – has been anathema to the scientific establishment.

According to the author, Western society has been guilty of emotional exceptionalism since the 17th century, when Descartes concluded that, unlike ourselves, animals were automata devoid of reason or feeling. De Waal argues that this flies in the face of modern neuroscience. His book is a Janus-faced exercise. It is largely a journey through emotions in ourselves and other species, and how they function in all these animals. He then uses the data as a springboard for a reverse excursion into their implications for human thought and society.

Before assembling his conclusions, however, de Waal has first to sweep away some of the understorey that has obscured understanding. One problem is the dualism between mind and body so engrained in Western ideas. For de Waal this ignores all the evidence that they are completely integrated and that emotions themselves function within this psycho-physical whole.

The author also draws a precise distinction between feelings and emotions. The former are private and internal, the unknowable parts of our subjective lives. None of us can ever know when we speak of “love” that any two persons are referring to exactly the same experience. Animal feelings are thus equally inaccessible. Emotions, on the other hand, are verifiable. They are manifest through external physical gestures. Studies involving many highly divergent human cultures have shown that there is a basic set of physical and facial movements common to all emotional expression. Deaf and blind children, with no opportunity to learn or copy received expressions, demonstrate the same repertoire for these emotional states.

In short, emotions are rooted in biology and de Waal likens their function to internal organs that are essential to the well-being and health of their owners. Sometimes we can also identify the underlying neurochemical processes that activate them, even in the case of love. Human couples who are romantically attached exhibit higher levels of oxytocin in their bodies than single people. This ancient neuropeptide is also released when humans engage in sex, nursing and birthing, but the neural similarities with other species are striking, even when the subjects are rodents.

De Waal gives the example of prairie voles, which live lives of strict monogamy and, in turn, possess high levels of oxytocin. If a prairie vole loses its partner it exhibits brain activity closely corresponding to stress and depression. It also shows passivity in the presence of danger as if it no longer cares whether it lives or dies.

Another of the book’s striking revelations is that rats have been clinically proven to enjoy tickling and play. The Swiss scientists who conducted the work could tell which of the rodents had received such stimulation simply from the pinker appearance of their ears. Rats, in turn, showed a preference for sitting close to images of their fellows with relaxed faces, rather than those expressing pain.

Even more remarkable are de Waal’s examples of altruism among animals, such as the rats that attempted to free a trapped fellow before feeding. Another test revealed the sense of fairness existing among capuchins by rewarding two monkeys with unequal amounts of food. The short-changed individual soon made powerful demonstrations of disgust and protest. Conversely, apes that received more than their due share exhibited what is called second-order fairness and a wish to have their own rations distributed more equably.

Ironically there is one emotional state that science has often been willing to concede among our fellow primates: aggression. De Waal points to a continuum of ideas running from Thomas Hobbes, through Freud and even Churchill, to modern behavioural scientists that have overemphasised the will to power as the driver in primate/human behaviour. The gist of the argument is that we are hardwired for violence, or as Churchill put it, “The story of the human race is war.”

In fact, there is little anthropological evidence for war prior to the Neolithic. Not that de Waal is unwilling to attribute aggression to ourselves or chimpanzees. On the contrary, he even suggests that in certain cases our closest relatives are capable of something akin to murder. Yet perhaps his most illuminating commentary is about science’s broader unwillingness to investigate the female-dominated, highly pacific social world of pygmy chimpanzees or bonobos. This remarkable primate species of the Congolese rainforest is matriarchal and resolves most disputes with frequent recreational sex.

Bonobos also possess the closest limb-to-body-length ratio to humans, suggesting our common ancestry. Yet de Waal argues that primatologists have focused on male aggression in the other chimpanzee because it more closely accords with ideas about humankind’s own tendencies. In short, the peacefulness of bonobos doesn’t fit our fundamental intellectual bias.

De Waal concludes by suggesting that, far from being an exclusive human property, emotions are common to all animals and that their full investigation will become the next major frontier in behavioural studies. It is when the author turns to the implications of all this that his reflections are weakest. His best suggestions include a rather self-serving point that zoos are important repositories for dwindling mammal genes and that supermarkets could carry barcodes on meat products that triggered smartphone images of the living conditions for the dead animals on sale.

When the rest of life on Earth is threatened by a tsunami of human population growth and all its destructive implications, surely these solutions sound small-scale, even trivial. If complex emotions really are a common heritage of the whole animal kingdom, then we need to reimagine our responsibilities to, and relationship with, those creatures that share this planet. Yet de Waal should be congratulated for assembling such a powerful body of evidence from which that process can begin.

Mark Cocker’s most recent book is “Our Place: Can We Save Britain’s Wildlife Before It Is Too Late?” (Jonathan Cape)

Mama’s Last Hug: Animal Emotions and What They Tell Us about Ourselves

Frans de Waal

Granta, 348pp, £14.99