What Makes Us Human?

What makes us human? This question has puzzled thinkers, scientists, and philosophers for centuries. In his book "What Makes Us Human?", Charles Pasternak explores the various traits and abilities that set our species apart from other animals. Drawing on insights from genetics, psychology, anthropology, and other fields, Pasternak examines the key factors that have shaped human evolution and defined our unique place in the natural world.

The book delves into topics like human cognition, language, imagination, curiosity, social behavior, and technological innovation. By analyzing these distinctly human characteristics, Pasternak aims to uncover the essence of what it means to be human. He considers perspectives from a range of experts to paint a multifaceted picture of human nature and our species' special capabilities.

As you'll see in this summary, there's no simple answer to what makes us human. Our humanity emerges from a complex interplay of biological, psychological, and cultural factors. But by exploring the various theories and evidence, we can gain fascinating insights into the unique qualities that define our species.

The Genetic Foundations of Human Cognition

One of the most obvious things that sets humans apart from other animals is our advanced cognitive abilities. We can think abstractly, solve complex problems, and ponder our own existence in ways that other species cannot. But where do these superior mental capabilities come from?

According to geneticist Walter Bodmer, the roots of human cognition lie in our DNA. While humans share about 99% of our genetic material with chimpanzees, that 1% difference translates to around 250 genes that are unique to our species. Bodmer believes these genetic variations are what gave rise to our enhanced cognitive powers.

However, pinpointing the exact genetic sequences responsible for human intelligence has proven challenging. In 2006, biostatician K.S. Pollard and her colleagues made an important breakthrough. They identified 49 areas of mammalian DNA that had remained largely unchanged for millions of years, but then rapidly evolved after humans split from chimpanzees. These regions may hold the key to our cognitive uniqueness.

But genetics alone can't explain the full range of human mental abilities. Our capacity for music, mathematics, and other complex skills isn't directly tied to natural selection and evolution. Culture also plays a major role in shaping human cognition. A baby born to an isolated Amazonian tribe would think and act like a Westerner if raised in Britain from infancy.

So while our genes laid the foundation for advanced cognition, the human mind emerges from a complex interplay of biology and culture. Our genetic heritage gave us the hardware, but our cultural software allows us to reach our full cognitive potential.

Memes: The Cultural Building Blocks of Humanity

If genes aren't the whole story, what else makes humans unique? British author Susan Blackmore argues that we are defined by our ability to transmit and replicate memes - ideas, behaviors, and cultural information that spread from person to person.

Memes are like mental genes. They include everything from catchy tunes and popular sayings to scientific theories and religious beliefs. Humans are the only true "meme machines" on Earth. While other animals pass on some instinctive behaviors genetically, only humans have the ability to rapidly spread ideas and cultural innovations through non-genetic means.

Interestingly, memes behave somewhat selfishly, like genes. They evolve and spread based on their own "fitness," not necessarily to benefit their human hosts. The memes that replicate most accurately and appeal to human minds tend to survive and proliferate in society.

This memetic evolution has shaped human culture and cognition over time. For instance, certain sounds in language become more common as they are easier to reproduce accurately. This in turn may have influenced our genetic evolution, as better language skills likely conferred reproductive advantages.

So in Blackmore's view, it's our unparalleled ability to generate, transmit, and evolve memes that truly sets humans apart. We're not just biological organisms, but vehicles for the replication and spread of ideas and cultural information.

Mental Time Travel: Reliving the Past and Imagining the Future

Another key aspect of human cognition is our ability to mentally travel through time. As psychologists Michael C. Corballis and Thomas Suddendorf explain, humans have a unique capacity to vividly recall past experiences and imagine potential futures.

This mental time travel is made possible by our episodic memory - the ability to consciously remember specific events and experiences. Unlike semantic memory (memory of facts and general knowledge), episodic memory allows us to mentally relive past moments in rich detail.

But we don't just remember the past - we can also project ourselves into hypothetical future scenarios. This ability to simulate potential outcomes gives humans a major survival advantage. We can anticipate challenges, plan ahead, and make decisions based on imagined futures.

While some animals show basic future planning abilities (like crows making tools to use later), human mental time travel is far more sophisticated. We can generate vivid, detailed mental simulations of both past and future events. We can also share these mental experiences with others through language.

This capacity for mental time travel is closely linked to human language abilities. By describing remembered or imagined scenarios to others, we can share knowledge and experiences across time and space. This allows human culture and knowledge to accumulate in ways not possible for other species.

So our ability to transcend the present moment through memory and imagination is a defining feature of human cognition. It allows us to learn from the past, plan for the future, and share our mental experiences with others in uniquely human ways.

The Power of Imagination

While our ability to remember and anticipate is impressive, psychologist Robin Dunbar argues that it's our capacity for imagination that truly sets humans apart. We can step back from reality and ask "what if?" in ways that even our closest primate relatives cannot.

This imaginative ability underlies many distinctly human endeavors. Religion requires us to imagine unseen deities and spiritual realms. Literature transports us to fictional worlds. Science advances through imaginative theories about how the universe works. Without imagination, these cornerstones of human culture would not be possible.

Crucially, humans also possess "theory of mind" - the ability to imagine and understand the mental states of others. We can attribute beliefs, desires, and intentions to other people. This emerges around age 4 in children and allows for complex social interactions and empathy.

Other primates, in contrast, seem limited to understanding their own mental states. They have "first-order intentionality" (awareness of their own beliefs), but struggle with higher levels of mental attribution. Adult humans can achieve up to "fifth-order intentionality," allowing us to navigate incredibly complex social situations.

Our imaginative capabilities build as we develop. While babies and apes have only first-order intentionality, by adulthood humans can handle convoluted chains of mental attribution (e.g. "I believe that he thinks that they want everyone to understand that we would like them to...").

This rich inner world of imagination and mental modeling gives humans unparalleled creative and social abilities. It allows us to innovate, empathize, and cooperate in ways no other species can match.

From Gestures to Speech: The Evolution of Human Communication

While language is often cited as a uniquely human trait, physiologist Maurizio Gentilucci and psychologist Michael C. Corballis argue that it's specifically our capacity for speech that sets us apart. They propose that human language evolved from a system of gestures to our current speech-based communication.

Early human ancestors likely communicated primarily through hand and body gestures, similar to how modern apes communicate. They may have pointed to objects or mimed actions to convey meaning. This visual communication system worked well for concrete concepts but had limitations for expressing abstract ideas.

Over time, our ancestors began incorporating facial expressions and vocalizations into their gestural language. Gradually, these vocal elements became the dominant form of communication, evolving into the speech-based languages we use today.

This shift from visual to vocal communication offered several evolutionary advantages:

1. It freed up the hands for other tasks while communicating.
2. It allowed for communication over longer distances and in low-light conditions.
3. It enabled more complex and abstract ideas to be expressed efficiently.

Interestingly, studies have shown connections between hand and mouth movements in both monkeys and humans. This suggests that our speech may have evolved from a gestural system, with the vocal apparatus taking over functions originally performed by hand gestures.

The development of speech and complex language had profound implications for human evolution. It allowed for more sophisticated social cooperation, the transmission of knowledge across generations, and the development of abstract thought. In many ways, our unique linguistic abilities laid the groundwork for the complex cultures and civilizations that define humanity today.

The Human Mind: More Than Just a Brain

While our cognitive abilities clearly stem from our brains, Reverend Richard Harries argues that the human mind is more than just a physical organ. He proposes that humans are "half ape, half angel" - part biological organism and part spiritual being.

The "half ape" part of us refers to the similarities we share with other primates. Our brains function in many of the same ways as our evolutionary cousins. But Harries contends that humans also have a "half angel" nature that goes beyond the physical brain.

This spiritual side manifests in our capacity for rational reflection and our drive for spiritual meaning. Humans can contemplate abstract moral principles, weigh the pros and cons of complex decisions, and ponder the nature of existence itself. We also engage in spiritual quests, seeking connection with the divine or exploring the deeper meaning of life.

Harries argues that this spiritual dimension stems from humans being made "in the image of God." While this is a religious perspective, it highlights the difficulty in reducing human consciousness entirely to brain function. Our subjective experiences of spirituality, morality, and self-awareness seem to transcend pure biology.

This doesn't mean humans have literal immortal souls separate from our bodies. Rather, Harries suggests we are "psychophysical unities" - integrated beings with both physical and mental/spiritual aspects. This unity begins with God (in his view) and gives humans our unique capacity for understanding and spiritual seeking.

While other animals may show some signs of consciousness, they don't display the rich inner worlds of humor, inspiration, self-sacrificing love, and spiritual longing that characterize human experience. Our ability to understand ourselves in relation to the world - our human consciousness - sets us apart.

Importantly, this consciousness allows humans to change ourselves through conscious effort. Research has shown the brain to be neuroplastic - able to rewire itself based on our thoughts and behaviors. By understanding how our minds work, we can intentionally reshape our thought patterns and actions.

So while rooted in our physical brains, the human mind transcends pure biology. Our capacity for rational reflection, spiritual seeking, and conscious self-transformation makes us unique among Earth's creatures.

The Evolution of the Human Brain

Our advanced cognitive abilities are clearly linked to our unusually large brains. But how and why did the human brain evolve to be so much larger than those of our primate relatives?

Geneticist Stephen Oppenheimer argues that successive ice ages during the Pleistocene epoch (starting about 2.5 million years ago) drove the evolution of larger brains in our ancestors. As the climate became colder and drier, having a more energy-intensive but capable brain provided a survival advantage.

The fossil record shows that each new human ancestral species that emerged after an ice age had a larger brain than its predecessors. Between 2.5 million and 1 million years ago, the brain volume of our ancestors increased from about 400 to 1,000 cubic centimeters.

But why did only human brains grow larger while other animals' remained the same size? The development of language appears to be a key factor. Our ancestors' brains didn't start growing significantly until after they began speaking. The species Homo heidelbergensis, for instance, could speak for over 500,000 years before their brain size increased dramatically.

This ties into psychologist Mark Baldwin's theory that a species' behavior can influence natural selection. He proposed that learned habits (like language use) can alter the environment, causing natural selection to favor physical and behavioral traits best suited to the new conditions.

If Baldwin's theory is correct, the emergence of language reshaped our ancestors' environment to favor those most adept at communication. This, in turn, drove the evolution of larger brains better equipped for complex language and abstract thought.

So the interplay between environmental pressures, language development, and brain evolution helped create the uniquely capable human mind. Our ancestors' ability to adapt to harsh ice age conditions through improved cognition and communication set us on the path to becoming the dominant species on the planet.

Human Curiosity: The Drive to Explore

While many animals display some level of curiosity, biologist Charles Pasternak argues that the intensity of human curiosity is unmatched in the natural world. This powerful drive to explore and understand our environment is a defining characteristic of our species.

All organisms exhibit some form of curiosity or environmental responsiveness. Plants, for instance, display phototropism - growing towards light sources. Animals often explore beyond their usual habitats, driven by an innate curiosity about their surroundings.

But human curiosity goes far beyond these basic impulses. We have an insatiable desire to understand how things work, to push the boundaries of knowledge, and to venture into the unknown. This intense curiosity has driven us to explore the depths of the oceans, the far reaches of space, and the fundamental building blocks of matter itself.

Pasternak identifies four key attributes that may have contributed to the development of human curiosity:

1. Upright gait: Walking on two feet allowed us to better survey our surroundings and freed our hands for manipulation and tool use.

2. Flexible thumbs: Our dexterous hands enabled us to craft tools, create art, and interact with our environment in complex ways.

3. Advanced larynx: The human voice box allows for a wide range of vocalizations, leading to the development of complex language.

4. Larger brain: Humans have about three times as many cortical neurons as apes, giving us greater cognitive processing power.

These attributes worked together to enhance our ability to explore and understand our world. Our upright posture and dexterous hands allowed us to manipulate objects and create tools. Our advanced vocal abilities enabled us to communicate complex ideas and share knowledge. And our larger brains gave us the processing power to make sense of the information we gathered.

Brain scans have even shown that the regions associated with exploratory decision-making are larger in humans than in other primates. This suggests that curiosity and the drive to explore are hardwired into the human brain to a greater degree than in our closest relatives.

This intense curiosity has been a driving force behind human progress. It has led us to develop science, technology, art, and philosophy. It has pushed us to explore every corner of our planet and beyond. In many ways, our unquenchable thirst for knowledge and understanding is at the heart of what makes us human.

The Power of Symbolic Thought and Language

Paleoanthropologist Ian Tattersall argues that humans are unique in our capacity for symbolic thought and language. While other animals can communicate and solve problems, only humans can create and manipulate abstract symbols to represent both concrete objects and intangible concepts.

Humans have the ability to mentally divide the world into symbolic entities and assign names or labels to these different pieces of existence. We can use words to represent physical objects like "tree" or "rock," but we can also create symbols for abstract ideas like "love," "justice," or "infinity."

Moreover, we can combine and recombine these symbols in novel ways to create new meanings. We can ask hypothetical questions like "What if trees could talk?" or make abstract statements like "Justice is blind." This symbolic flexibility allows us to imagine alternative realities and think about the world in highly creative ways.

The human capacity for symbolic thought likely emerged with the rise of Homo sapiens around 200,000 to 150,000 years ago. However, it wasn't until the development of language that this potential was fully realized. Language provided the tool needed to express and communicate symbolic ideas.

Initially, early language was likely used primarily for basic communication of needs and immediate concerns. Over time, it evolved to express more abstract and symbolic concepts. This co-evolution of language and symbolic thought dramatically expanded human cognitive capabilities.

Language relies on the formation and combination of mental symbols to produce new meanings and associations. It allows us to share complex ideas, tell stories, and pass knowledge from one generation to the next. Without language, the kind of abstract, symbolic thinking that characterizes human cognition would be impossible.

This symbolic intelligence stems from the human mind and our capacity for conscious thought. However, the exact physical differences in the brain that allow for this ability remain somewhat mysterious. Despite the high similarity between human and chimpanzee brains, only humans have developed this sophisticated capacity for symbolic thought and language.

The emergence of symbolic thinking and complex language marked a major turning point in human evolution. It allowed for the development of culture, art, religion, and science. It enabled humans to cooperate on a large scale and to accumulate knowledge over generations. In many ways, our mastery of symbols and language is what has allowed human civilization to flourish.

The Social Nature of Humanity

Psychologist Andrew Whiten contends that it's not just our intelligence that sets us apart, but our deep social nature. Humans are arguably the most social creatures on Earth, with complex social structures and behaviors that go far beyond those of other species.

Whiten identifies four key elements that make up the human "deep social mind":

1. Mind-reading: The ability to predict and explain others' actions based on their mental states (thoughts, desires, beliefs). This "theory of mind" allows us to navigate complex social situations.

2. Culture: Much of our mental content is shaped by the culture we live in. We acquire vast amounts of information socially, through traditions, customs, and shared practices.

3. Language: Our linguistic abilities allow us to transmit thoughts and ideas from one mind to another, facilitating complex social interactions and knowledge sharing.

4. Cooperation: Humans have unique capacities for group coordination and equitable resource sharing. We can work together in large groups towards common goals.

These social abilities likely evolved in response to environmental pressures. As our ancestors moved from forests to savannas, they had to compete with better-adapted predators. Developing strong social skills and the ability to cooperate in groups gave early humans a survival advantage.

By working together, our ancestors could communicate during hunts, interpret animal tracks collectively, assign roles for group defense, and fairly divide food resources. This social cooperation allowed humans to thrive in challenging environments where individual efforts would have failed.

Our deep social nature has profound implications for human cognition and behavior. Much of our thinking is oriented around social concerns - how others perceive us, how to navigate relationships, how to cooperate effectively in groups. Our identities and worldviews are shaped by the cultures we grow up in.

This social orientation distinguishes us from even our closest primate relatives. While other apes show some social behaviors, they lack the depth of social understanding and cooperation seen in humans. Our ability to form large, complex societies built on shared cultural knowledge is unparalleled in the animal kingdom.

So while our intelligence is certainly a key part of what makes us human, our profound sociality is equally important. Our cognitive abilities evolved in a social context, and much of what we consider uniquely human emerges from our deep capacity for social interaction and cooperation.

Understanding Cause and Effect

Biologist Lewis Wolpert argues that one of the key things separating humans from other animals is our ability to understand cause and effect relationships. This causal reasoning ability underlies much of human technological and cultural development.

From a very young age, humans start to grasp basic cause-effect relationships. By age two, children understand that a rolling ball will cause a stationary ball to move when they collide. This fundamental grasp of causality forms the basis for more complex reasoning as we develop.

Other primates, in contrast, struggle with understanding causality. In one experiment, it took macaques 50 half-hour sessions to figure out how to use a stick to retrieve food through a fence. Human children grasped the solution almost immediately. The macaques could eventually solve the problem through trial and error, but they lacked the causal understanding to reason out the solution quickly.

This ability to reason about cause and effect has been crucial for human technological development. Technology, at its core, involves intentionally manipulating the environment to improve survival chances. It requires understanding how different actions and tools will produce desired effects.

Our causal reasoning abilities allow us to engage in mental trial and error - imagining different possible actions and their likely outcomes before actually trying them. This lets us innovate and problem-solve much more efficiently than species that rely solely on physical trial and error.

Causal understanding also underlies many other uniquely human abilities:

• Scientific thinking relies on identifying cause-effect relationships in nature.
• Complex planning requires projecting how current actions will affect future outcomes.
• Many aspects of language involve expressing causal relationships between ideas.
• Social reasoning often involves inferring the causes of others' behaviors.

So while other animals may show some basic understanding of cause and effect in limited contexts, the human capacity for causal reasoning is far more sophisticated and generalizable. This ability has allowed us to reshape our environment, develop advanced technologies, and build complex cultures in ways no other species can match.

Cooking: The Culinary Key to Humanity

Primatologist Richard Wrangham makes the intriguing argument that it's not just our big brains or social nature that defines us - it's our ability to cook food. He contends that humans are essentially "cooking animals," and that this culinary innovation played a crucial role in our evolution.

Humans are the only animals that consistently cook their food. While this might seem like a minor cultural practice, Wrangham argues it has profound biological and evolutionary implications:

1. Cooking makes food more calorically efficient. Raw diets often can't provide enough calories for human survival, especially in the wild.

2. Cooked food is easier to digest, allowing our bodies to extract more nutrients with less effort.

3. Cooking likely influenced human anatomy, leading to smaller teeth and digestive tracts compared to our ancestors.

4. The practice of cooking may have emerged as early as 1.8 million years ago, potentially driving major changes in human evolution.

The ability to cook opened up new food sources and made existing ones more nutritious. This allowed early humans to thrive in a wider range of environments and may have contributed to brain growth by providing more readily available energy.

Cooking also had significant social implications. It encouraged food sharing, division of labor, and social gathering around hearths. These behaviors likely strengthened social bonds and cooperation within early human groups.

While the exact timing of when humans first controlled fire and began cooking is debated, the impact of this innovation is clear. Cooking shaped not just our diets, but our biology, social structures, and cognitive development.

Wrangham's "cooking hypothesis" highlights how a seemingly simple cultural practice can have far-reaching evolutionary effects. By harnessing fire to transform our food, early humans set in motion changes that would fundamentally reshape our species.

The Interplay of Biology and Culture

As we've seen throughout this summary, what makes us human isn't just our biology or just our culture - it's the complex interplay between the two. Our genetic heritage provided the foundation for uniquely human traits, but it's our cultural innovations that have allowed us to fully realize our potential.

Consider how our biological traits and cultural developments have reinforced each other:

• Our larger brains allowed for more complex cognition, which in turn drove the development of language and symbolic thought.
• Language and symbolism enabled the creation and transmission of culture, which further shaped our cognitive development.
• Our social nature led to the formation of complex societies, which then influenced our ongoing biological and cultural evolution.
• Technological innovations like cooking changed our biology, which then allowed for further cultural and technological advancements.

This dynamic interplay between biology and culture is what truly sets humans apart. We're not just intelligent apes, nor are we purely cultural beings divorced from our animal nature. We're a unique fusion of biological and cultural evolution.

Our genes gave us the capacity for advanced cognition, language, and social behavior. But it's our ability to create and transmit culture that has allowed us to accumulate knowledge, develop complex technologies, and reshape our environment in unprecedented ways.

This cultural accumulation has, in turn, changed the selective pressures acting on our biology. As we've seen with cooking, cultural practices can drive biological changes over evolutionary time. Our biology and culture have co-evolved, each influencing the development of the other.

Understanding this interplay is crucial for grasping what makes us human. We can't reduce our humanity to just our genes, our brains, or any single trait. It's the dynamic interaction of our biological heritage and our cultural innovations that has produced the rich, complex beings we are today.

Conclusion: The Multifaceted Nature of Humanity

As we've explored throughout this summary, there's no single, simple answer to what makes us human. Our humanity emerges from a complex interplay of biological, psychological, and cultural factors. Each of the perspectives we've examined sheds light on a different aspect of what sets our species apart:

• Our genetic uniqueness provides the foundation for our advanced cognitive abilities.
• Our capacity for mental time travel allows us to learn from the past and plan for the future.
• Our rich imaginative lives enable creativity, empathy, and complex problem-solving.
• Our linguistic abilities facilitate the sharing of knowledge and the development of culture.
• Our deep social nature allows for unprecedented levels of cooperation and cultural transmission.
• Our understanding of cause and effect drives technological innovation and scientific thinking.
• Our culinary practices have shaped our biology and social structures.

What emerges from these various perspectives is a picture of humanity as a uniquely adaptable and innovative species. We have the biological hardware to support advanced cognition, but it's our ability to create and transmit culture that truly sets us apart. This cultural capacity allows us to accumulate knowledge over generations, to create complex technologies, and to reshape our environment in profound ways.

Yet our humanity isn't just about our achievements or abilities. It's also about our inner lives - our capacity for self-reflection, our search for meaning, our ability to ponder our own existence. These more subjective aspects of human experience are harder to quantify, but they're no less essential to what makes us human.

In the end, what makes us human is not any single trait, but the unique combination of characteristics that allow us to be both part of nature and shapers of it. We are biological beings deeply rooted in our evolutionary past, yet we're also cultural creatures capable of imagining and creating new realities.

Understanding our multifaceted nature can help us appreciate both our potential and our limitations as a species. It can inform how we approach challenges, how we structure our societies, and how we envision our future. By embracing the complexity of what makes us human, we can strive to cultivate the best aspects of our nature while mitigating the less desirable ones.

As we continue to evolve both biologically and culturally, the question of what makes us human will likely remain a subject of fascination and debate. But by exploring it, we not only learn about our species - we also gain insights into ourselves as individuals and our place in the broader tapestry of life on Earth.