There really is something unique about the human species that needs explanation.
Below is a partial list of unique human characteristic compiled by Ajit Varki and Danny Brower in their book.
Many more examples of human uniqueness and research can be found here.
No expert on any other species could produce as deep and broad a list of unique characteristics for their species. Nor can any other species write their own list and invent a theory to explain them.
“If you look through this website, you will find many examples of complex human activities, behaviors, and mental abilities that should not necessarily require a full Theory of Mind (ToM). Examples include such things as lasting friendships, cooperative breeding, basic tool making, the construction of shelters, cooking, use of a home base, a sense of fairness, assistance with childbirth, peacemaking, sharing of food, imitation, group hunting, and so on. Of course many of these activities would be facilitated if full ToM ability were available. But having a full ToM is an essential ingredient for many other uniquely human mental abilities that we take for granted. The following examples are randomly chosen and presented in alphabetical order (a much longer list is obviously possible).
1. Acting (dramatics). Acting does not even require language, as an actor can just mime. But in order to be successful, actors must be aware that they are putting themselves in the mental shoes of someone else—the person they are pretending to be. The actor also has to be aware that audience members have independent minds that are capable of appreciating the performance. This is true even when the actor is in front of a camera, knowing that someone, somewhere, could either be watching live or even viewing a tape of the performance after the fact. Comedic performances are a variant of acting. Chimpanzees can manifest a form of laughter and may show amusement at physically unusual events. But for a stand-up comedian to make others appreciate humor and laugh in response, she or he has to be aware that the people seeing the performance have minds capable of understanding the humor. Conversely, those observing the performance must understand that the comedian has a mind that is independent. Note that, like acting, comedic performance does not necessarily require spoken language.
2. Blushing. Charles Darwin commented that blushing might be a uniquely human behavior. It remains possible that some form of blushing occurs in other species and we just cannot detect it. But according to the standard definition, blushing requires that one be suddenly ashamed or embarrassed in the presence of others. And it is not possible to feel such emotions unless one is aware that others have minds like one’s own and are therefore capable of recognizing one’s embarrassment or shame. Of course it is unclear what the adaptive value is of betraying a negative self-evaluation. Perhaps this is related to the importance of sociability and accountability in human societies.
3. Care of the infirm and elderly. Humans are unique among living animals in that we take active and extensive care of the sick and elderly within our groups. In order to do so optimally, the humans doing the caring need to be aware that those being helped have minds of their own. Indeed, this can be a reciprocal behavior. Interestingly, there is evidence that some elderly Neandertals with healed severe injuries survived within their groups, indicating that our closest extinct evolutionary cousins likely had a degree of empathy and sufficient ToM to recognize the needs of an old or disabled person.
4. Concern for posthumous reputation. Many social animals pay close attention to their status, rank, and reputation within their group. But some humans also seem to be concerned about their status and reputation after they are dead and gone—their “legacy.” Why would that be, since we are no longer there to witness what others have to say about us after we are dead? It appears that we can project ourselves into that distant future and imagine how others who are still alive are thinking about us—and even imagine that our own minds are there, reacting to what others are saying about us. This kind of “mental time travel” is likely unique to humans, and would be hard to imagine if we did not have a ToM of others (a more realistic view of immortality comes from Woody Allen, who said: “I don’t want to live on in the hearts of my countrymen; I want to live on in my apartment”). This concern for posthumous reputation might also be partly explained by the discovery of the “end history illusion”––when studied, people of all ages “believed they had changed a lot in the past but would change relatively little in the future. People seem to regard the present as a watershed moment at which they have finally become the person they will be for the rest of their lives” (and presumably beyond their deaths).
5. Death rituals. All human societies carry out some form of death-related ritual, indicating that humans not only recognize the deaths of others as individuals but also recognize the fact that the person who died is no longer among us. Some other animals, such as elephants, crows, and chimpanzees, seem to have a rudimentary understanding of the death of one of their own (more on this later). But these behaviors pale in comparison to the human grief response, which stretches on from vocal private and public grieving and funerary rites to memorials, death anniversaries, and the like. These behaviors would not occur unless the individuals carrying out the rituals are fully aware that someone with a mind like theirs is no longer alive. Having developed a full ToM of other humans, we can then ascribe personhood to pets (and even to inanimate objects) and thus grieve for their loss.
6. Food preparation for others (cuisine). Although other animals do process foods, and some may even do so for the benefit of other individuals, humans are unusual in the extent to which we modify, process, and cook foods in special ways, often with the goal of pleasing others. To do this, the chef needs to be aware that the individuals for whom the food is being prepared have minds of their own. The chef also must want them to appreciate the cuisine. Note that cuisine is not the same as mere cooking, which may go further back in our ancestry—perhaps more than a million years, as suggested by Richard Wrangham.
7. Grandmothering. All human societies have grandmothers. Even in societies where the average life span is very short, there are typically a few old women surviving. Such postmenopausal women who are no longer at reproductive age have been a puzzle from the evolutionary perspective, as the ability to reproduce is the usual driver of natural selection. The “grandmother hypothesis” put forward by Kristen Hawkes and others is currently the best explanation for this phenomenon. The idea is that by living past menopause a grandmother continues to contribute to the propagation of her genes by aiding the survival of grandchildren who are still helpless enough to benefit from her assistance. Of course we don’t know whether living longer came first, thus exposing menopause, or whether grandmothers were first selected for living longer because of the value of having menopause. Regardless of whether the theory stands the test of time, the fact remains that with the possible exception of certain long-lived social female whales that have postmenopausal life spans, no other species seems to have true grandmothers. There are certainly elephant packs and primate troops that feature an elderly matriarch surrounded by her daughters (or possibly her sons, in the case of bonobos). But there is so far no evidence that these old, intelligent, highly social females specifically recognize their own grandchildren and give selective attention to them. The difference in humans is, of course, striking, as grandmothers typically dote upon their grandchildren even more than mothers do and go out of their way to provide help. Think about this in the context of ToM: It is instinctively easy for a mother to recognize her own offspring because of the bonding experiences of childbirth, infant care, and breast-feeding. But in order to recognize a grandchild, the grandmother not only has to define her progeny but also know who their offspring are, as distinct from other young ones in the group. It seems reasonable to suggest that a full ToM would make it much easier for a grandmother to recognize her grandchildren as individuals with unique minds that need to be doted upon.
8. Healing of the sick. All human societies make attempts to heal the sick. Such attempts—although variably successful—indicate that humans are aware of the suffering of a sick person and that the sick person is an individual with a mind. The noble and underappreciated profession of nursing best exemplifies this human trait.
9. Hospitality. Almost all human societies show some form of hospitality, at least for members of their own society (something that other animals rarely do). In order to be truly hospitable, one has to recognize that those at the receiving end have minds of their own and can appreciate the hospitality. And, conversely, those giving the hospitality can expect reciprocity in the future.
10. Inheritance rules. Most human societies have inheritance rules, ranging from highly rigid to fairly flexible. To decide upon a beneficiary, you have to know that the chosen heir is a person with a mind and that you will likely die prior to that individual. Again, it is hard to imagine how this is possible without a full ToM. And in the case of those humans who leave their inheritance to a favorite pet, there was human recognition of the pet as an individual.
11. Laws and justice. The existence of specific laws and concepts of justice are common to most human cultures. Even the most tolerant societies have some defined form of punishment for inappropriate behavior. In order to develop laws and a sense of justice, people have to first know that other individuals have minds and are capable of intentional wrongdoing. This allows the society to think ahead to that possibility, generate rules and regulations, and then mete out justice when an individual fails to follow the law. Moreover, modern laws acknowledge that someone can commit a crime yet be “not guilty by virtue of mental disability” (often, such a defendant does not possess a healthy ToM). It is interesting that we humans care so much about justice that we are even willing to pay a personal price (such as risk of retribution) in order to ensure that wrongdoers get punished.
12. Lecturing. This is something that happens in all human societies (if one includes storytelling). In order to lecture or tell a story, one has to know that the audience consists of individuals with minds like one’s own, even if there are perhaps minor individual differences among them. Success also requires that audience members recognize that the individual doing the lecturing or storytelling has a mind. And one of the rules of thumb for good lecturing is to put oneself in the minds of audience members. Obviously, this is difficult to do without a full ToM.
13. Multi-instrumental music. Group playing of musical instruments is common to almost all human societies. Whether in a quartet or a huge orchestra, though, participating musicians must know that the other musicians have minds of their own. This type of interaction reaches its pinnacle in Indian classical music and in the jam sessions of jazz, in which it really seems that the musicians are reading each other’s minds while improvising. Of course, when there is an orchestra conductor involved, she or he is not only reading the minds of all the musicians but also expecting them to read his or her mind. Group singing in multipart harmony is a variation on the same theme.
14. Organized sports. Group sporting activities of various kinds are also found in most human societies. While play involving multiple individuals does occur in other species and sometimes follows certain basic principles (e.g., lion cubs don’t actually hurt each other when roughhousing), highly organized sports with rigid and arbitrarily specified sets of rules are uniquely human. It would be hard to play such games if one does not know that one’s team members also understood the arbitrary rules. In addition, trying to “read” the minds of one’s opponents can be helpful. Formal sports often have a referee, and the players must understand that the referee has a mind of his or her own so that they can follow what that individual dictates. Cooperation and competition in service of a nonessential goal is the underlying notion of most sports.
15. Religiosity. Although not all humans are religious, some form of religion is universal in almost all societies (though not in all individuals in all societies). The numerous gods described by various cultures all require that devotees have ToM, as one needs to imagine the minds of gods in order to even have such a concept. The experience of having ToM could also allow humans to attribute mental states to inanimate objects, such as rocks and trees, forming the basis for animistic religions. There are of course many other cogent arguments for the adaptive value of religiosity in human evolution31 and equally robust claims that established religions are now causing more harm than good.
16. Romantic infatuation. Technically called limerence, romantic infatuation is common to many cultures and ranges from special interest in another person to all-consuming love affairs. While animals can certainly become fast friends (strange combinations of carnivores and herbivores can even become friends under unusual circumstances), the widespread phenomenon of intense romantic infatuation in humans requires something approaching ToM.
17. Social control of paternity. This practice remains common in many human societies, and is often dictated by the elders in a given group. In order to control mating in this manner, the elders have to understand that younger individuals have minds of their own that need to be controlled. And when romantic infatuation conflicts with culturally prescribed mating rules, it can generate some of the great tragic love stories we are all familiar with in our respective cultures.
18. Teaching. Imitation is common in many animals, and can be taken to quite remarkable extents in some birds, such as parrots interacting with humans. But while cats may show their kittens how to play with dead mice, or chimpanzee mothers may allow their young ones to try cracking nuts, only humans take teaching to the extreme of carefully monitoring, correcting, and demonstrating specific behaviors and skills—usually to younger individuals using tested methods that vary with each society. Such active and directed instruction obviously requires the teacher to understand that the student has a mind capable of understanding what is being taught, and this knowledge must be reciprocal. Teaching also often involves slowing and exaggerating specific motions. In this case, both parties need to understand that the exaggerated motion is not what is done when the skill is actually mastered; it is used only in service of learning that mastery.
19. Torture. This horrible practice is common to many human societies and varies in its frequency, depending on social conditions and other factors. Although cats or chimpanzees might play with half-dead prey, active torture that is directed, continuous, and designed to break the spirit of the other individual (even while keeping the person alive) is a uniquely human phenomenon. Obviously, the most effective torturer is the one who can put himself in the mind of the person being tortured.
20. Trade. As Matt Ridley has emphasized in The Rational Optimist, bartering activities of various kinds are a quintessentially human phenomenon. In order to trade effectively, one has to understand the mind of the individual with whom one is trading and to realize the pros and cons of mentally interacting with that individual—and perhaps indirectly trading with the many others who later trade with that individual.”