With the discovery of fossils and scientific evidence, scientists have developed theories as well. While there may be no single conclusion, there is no doubt that humans are, indeed, unique.
In fact, the very act of contemplating what makes us human is unique among animal species. Most species that have existed on planet Earth are extinct, including a number of early human species. Evolutionary biology and scientific evidence tell us that all humans evolved from apelike ancestors more than 6 million years ago in Africa. Information obtained from early-human fossils and archaeological remains suggests that there were 15 to 20 different species of early humans several million years ago.
These species, called hominins , migrated into Asia around 2 million years ago, then into Europe and the rest of the world much later. Although different branches of humans died out, the branch leading to the modern human, Homo sapiens , continued to evolve. Humans have much in common with other mammals on Earth in terms of physiology but are most like two other living primate species in terms of genetics and morphology: the chimpanzee and bonobo, with whom we spent the most time on the phylogenetic tree.
However, as much like the chimpanzee and bonobo as we are, the differences are vast. Apart from our obvious intellectual capabilities that distinguish us as a species, humans have several unique physical, social, biological, and emotional traits.
Although we can't know precisely what is in the minds of other animals, scientists can make inferences through studies of animal behavior that inform our understanding.
Thomas Suddendorf, professor of psychology at the University of Queensland, Australia, and author of " The Gap: The Science of What Separates Us From Other Animals ," says that "by establishing the presence and absence of mental traits in various animals, we can create a better understanding of the evolution of mind.
The distribution of a trait across related species can shed light on when and on what branch or branches of the family tree the trait is most likely to have evolved.
As close as humans are to other primates, theories from different fields of study, including biology, psychology, and paleoanthropology, postulate that certain traits are uniquely human. It is particularly challenging to name all of the distinctly human traits or reach an absolute definition of "what makes us human" for a species as complex as ours.
Philip Lieberman of Brown University explained on NPR's "The Human Edge" that after humans diverged from an early-ape ancestor more than , years ago, the shape of the mouth and vocal tract changed, with the tongue and larynx, or voice box, moving further down the tract. The tongue became more flexible and independent and was able to be controlled more precisely.
The tongue is attached to the hyoid bone, which is not attached to any other bones in the body. Meanwhile, the human neck grew longer to accommodate the tongue and larynx, and the human mouth grew smaller.
The larynx is lower in the throats of humans than it is in chimpanzees, which, along with the increased flexibility of the mouth, tongue, and lips, is what enables humans to speak as well as to change pitch and sing. The ability to speak and develop language was an enormous advantage for humans. The disadvantage of this evolutionary development is that this flexibility comes with an increased risk of food going down the wrong tract and causing choking.
Human shoulders have evolved in such a way that, according to David Green, an anthropologist at George Washington University, "the whole joint angles out horizontally from the neck, like a coat hanger. The ape shoulder is better suited for hanging from trees, whereas the human shoulder is better for throwing and hunting, giving humans invaluable survival skills.
The human shoulder joint has a wide range of motion and is very mobile, affording the potential for great leverage and accuracy in throwing. Although other primates also have opposable thumbs, meaning they can be moved around to touch the other fingers, imparting the ability to grasp, the human thumb differs from that of other primates in terms of exact location and size.
This has given us better fine motor skills and the ability to engage in detailed precision work such as writing with a pencil. Although there are other mammals that are hairless—the whale, elephant, and rhinoceros, to name a few—humans are the only primates to have mostly naked skin. Humans evolved that way because changes in the climate , years ago that demanded that they travel long distances for food and water. Humans also have an abundance of sweat glands, called eccrine glands.
To make these glands more efficient, human bodies had to lose their hair to better dissipate heat. This enabled them to obtain the food they needed to nourish their bodies and brains, while keeping them at the right temperature and allowing them to grow.
One of the most significant traits that make humans unique preceded and possibly led to the development of other notable characteristics: bipedalism —that is, using only two legs for walking.
This trait emerged in humans millions of years ago, early in human evolutionary development and gave humans the advantage of being able to hold, carry, pick up, throw, touch, and see from a higher vantage point, with vision as the dominant sense. As human legs evolved to become longer about 1.
The observations mentioned above certainly contribute to our human character, but the following paragraphs give some of the unique aspects of humanity not attributable to any other part of creation, but to the present outworking of "what makes us human" and the choices we make.
Man was created to serve. Human ambition for the purpose of serving oneself certainly cannot provide anyone with the fulfillment they are seeking. There are many examples of people who became famous and wealthy, only to find there is no fulfillment in personal ambition.
The resulting disappointment in reaching personal goals and not finding fulfillment in them frequently leads to that individual's despair or eventual suicide. King Solomon, in the book of Ecclesiastes, described human ambition as "vanity" and "a chasing after the wind," concluding that man's only duty was to fear God and keep His commandments Ecclesiastes Certainly, a life spent not functioning as it was designed to leads only to frustration and misery. The role for man as a servant can be seen from the beginning of his creation.
Adam was created and placed in the Garden of Eden "to dress it and to keep it" Genesis The first recorded task man was given was to serve his Creator by caring for the Garden that He had planted. Christ emphasized the importance of the role of a servant many times to His disciples, teaching them that, "he that shall humble himself shall be exalted" Matthew He consistently used the concept of a servant as a synonym to describe those who would be His followers Matthew ; ; John Christ responded to the question of, "which is the great[est] commandment" by saying, "Thou shalt love the Lord thy God with all thy heart, and with all thy soul, and with all thy mind.
And the second is like unto it, Thou shalt love thy neighbor as thyself" Matthew , It may be easy to see that loving God with all your heart reflects a servant's attitude, but sometimes what it takes to love your neighbor as yourself is not as clear. When questioned about, "Who is my neighbor? This human behavior contrasts with a recent study of chimpanzee behavior revealing that chimpanzees are oblivious to the needs of others who are not related to them.
Paul Brand and Philip Yancey reported anthropologist Margaret Mead as saying, evidence for civilization is when a healed femur is found. It shows that someone must have cared for the injured person. Someone was a servant, evidence of "what makes us human. Whether we remember we were created to serve and do so, or choose not to fulfill what we were designed to do, may determine how fulfilled our life will be.
How is the value of a human determined? At one time in human history, slave traders would assess the value of a human based on the type and amount of work that an individual could perform for his "owner" just the same as if the person were an animal. Today the value of a human is determined by the individual's prospects for a quality life and by how much one can contribute to society.
This is evident by the treatment of the unwanted pre-born, the aged, and the infirmed. Mass slaughter of humans via legalized abortion, the push for legalization of doctor-assisted suicide, and the use of embryonic stem cells have defined what the worth of humans are by society. In addition to human value based on ethical ills, our culture is full of social ills that determine human value based on ethnic, social, or economic standing. Racial profiling and discrimination may be easy to recognize, but are all humans treated equally, regardless of their profession or economic standing?
Is the trash man, referee, or sales clerk, valued and treated the same as the doctor, entertainer, or pastor? James , What is the standard that determines human value? Scripture clearly teaches what the value of a human is.
Human life is to be valued from conception to old age Exodus 21 ; Matthew , is infinitely more valuable than other forms of creation Matthew ; , and each individual is equally valuable to God Colossians The value of a human in God's eyes is clearly stated in Romans They are so valuable that the Creator of the universe humbled Himself as a man and died a cruel death to reconcile Himself to His most valued creation.
Something must have happened in our evolution, Tomasello says, to make humans increasingly reliant on each other. Our brains needed fuel to get bigger and so collaborative hunting may have played a key role in that.
Our advanced teamwork may simply reflect our long history of working together to get food. The fact that our nearest relatives share too simply shows that it is an ancient trait. It was already present in the messy branch of early humans that led to us, but none of these other species were as hyper cooperative as we are today. Humans have a unique ability to understand the beliefs of another person Credit: Thinkstock.
These cooperative skills are closely tied to our incredible mind reading skills. We understand what others think based upon our knowledge of the world, but we also understand what others cannot know.
The Sally-Anne task is a simple way to test young children's ability to do this. The child witnesses a doll called Sally putting a marble in a basket in full view of another doll, Anne. When Sally leaves the room, Anne moves the marble to a box. Sally then comes back, and the experimenter asks the child where Sally will look for the marble.
Because Sally didn't see Anne move the marble, she will have a "false belief" that the marble is still in the basket. Most 4-year-olds can grasp this, and say that Sally will look in the basket. They know the marble is not there, but they also understand that Sally is missing the key bit of information. Chimps can knowingly deceive others , so they understand the world view of others to some extent.
However, they cannot understand others' false beliefs. In a chimpanzee version of the Sally-Anne task, researchers found that they understand when a competitor is ignorant of the location of food, but not when they have been misinformed. Tomasello puts it like this : chimpanzees know what others know and what others can see , but not what others believe. This tells us something profound about ourselves.
While we are not the only creatures who understand that others have intentions and goals, "we are certainly unique in the level of abstractness with which we can reason about others' mental states", says Katja Karg , also of the Max Planck Institute for Evolutionary Anthropology. Language gave us the skill to exchange complex thoughts and ideas Credit: iStock.
When you pull together our unparalleled language skills, our ability to infer others' mental states and our instinct for cooperation, you have something unprecedented. Just look around you, Tomasello says, "we're chatting and doing an interview, they chimps are not. We have our advanced language skills to thank for that.
We may see evidence of basic linguistic abilities in chimpanzees, but we are the only ones writing things down. We tell stories, we dream, we imagine things about ourselves and others and we spend a great deal of time thinking about the future and analysing the past.
There's more to it, Thomas Suddendorf , an evolutionary psychologist at the University of Queensland in Australia is keen to point out. We have a fundamental urge to link our minds together. We connect up our brains, and it's one of our defining traits Credit: SPL. That our rapidly expanding technology has allowed us all to become instant publishers means we can share such information at the touch of a button.
And this transmission of ideas and technology helps us in our quest to uncover even more about ourselves. That is, we use language to continue ideas that others put forward. Of course, we pass on the good and the bad. The technology that defines us can also destroy worlds.
Take murder. Humans aren't the only species that kill each other. We're not even the only species that fight wars. But our intelligence and social prowess mean we can do so on an unprecedented scale. We can fight and kill on an unparalleled scale Credit: istock. Charles Darwin, in his book The Descent of Man, wrote that humans and animals only differ in degree, not kind.
This still stands true but Suddendorf says that it is precisely these gradual changes that make us extraordinary and has led to "radically different possibilities of thinking". And it is these thoughts that allow us to pinpoint to our differences with chimpanzees.
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