Human self-reflection is the basis of philosophy and is present from the earliest historical records. Humanity has always taken great interest in itself. The human faculty of introspection, the urge of an individual to discover more about its essence, invariably leads to inquiry about the human condition and the essence of humankind as a whole.
Humans often consider themselves to be the dominant species on Earth, and the most advanced in intelligence and ability to manage their environment. This belief is especially strong in Western culture, and is derived in part from the biblical creation story in which Adam is explicitly given dominion over the Earth and all of its creatures.
Prehistoric notions about the status of humanity may be guessed by the etymology of ancient words for man. Latin homo (PIE *k■onyon) means "of the earth, earthling", probably in opposition to "celestial" beings. Greek ανθρωπος (mycenaean *anthrokwos) means "low-eyed", again probably contrasting with a divine perspective.
From the 3rd millennium Old Kingdom of Egypt, belief in the eternal afterlife of the human Ka is documented. From the earliest times, we make out a claim of dominance of humanity alongside radical pessimism because of the frailty and brevity of human life (In the Hebrew Bible, for example, dominion of man is promised in Genesis 1:28, but the author of Ecclesiastes bewails the vanity of all human effort).
Protagoras made the famous claim that "Man is the measure of all things; of what is, that it is; of what is not, that it is not". Socrates gave the (doubtlessly tongue-in-cheek) definition of humans as "featherless bipeds" (Plato, Politicus). More serious is Aristotle's description of man as the "communal animal" (ζωον πολιτικον), i.e., emphasizing society-building as a central trait of human nature, and "animal with sapience" (ζωον λογον εχων, animal rationale), a term that also inspired the species' taxonomy, Homo sapiens.
The dominant world-view of medieval Europe, as dictated by the Catholic Church, was that human existence is characterized by sin, and that its aim should be to prepare for divine judgement after death. The 13th century pope Innocent III wrote about the essential misery of earthly existence in his "On the misery of the human condition" – a view that was disputed by, for example, Gianozzo Manetti in his treatise "On human dignity".
See Renaissance humanism.
A famous quote of Shakespeare's Hamlet (II, ii, 115-117), expressing the contrast of human physical beauty, intellectual faculty, and ephemeral nature:
- What a piece of work is a man! How noble in reason! how infinite in faculties! in form and moving, how express and admirable! in action how like an angel! in apprehension, how like a god! the beauty of the world! the paragon of animals! And yet, to me, what is this quintessence of dust?
The Enlightenment was driven by a renewed conviction, that, in the words of Immanuel Kant, "Man is distinguished above all animals by his self-consciousness, by which he is a 'rational animal'". In the 19th century, Karl Marx defined man as "labouring animal" (animal laborans) in conscious opposition to this tradition. In the early 20th century, Sigmund Freud dealt a serious blow to positivism by postulating that human behaviour is to a large part controlled by the unconscious mind.
Comparison to other species
From a scientific viewpoint, Homo sapiens certainly is among the most generalized species on Earth. Smaller and simpler organisms such as bacteria and insects greatly surpass humans in population size and diversity of species, but few single species occupy as many diverse environments as humans. Many other species are adapted to specific environments, whereas humans use fire, clothing and manufactured shelter for protection against averse environmental conditions.
Various attempts have been made to identify a single behavioral characteristic that distinguishes humans from all other animals, e.g. the ability to make and use tools, the ability to alter the environment, language and the development of complex social structures. Considered in isolation, however, these differences are not absolute, as ethologists have recorded such behaviors in many species. Apes and even birds, for example, are known to "fish" for insects using blades of grass or twigs, and even to shape the tools for that purpose. For these reasons, the idea that making and using tools is a defining characteristic of humans is often considered outdated. Similarly, other animals often have methods of communication, but the degree to which humans create and use complex grammar and abstract concepts in language has not been seen in any other species (see also universal grammar).
Some anthropologists think that these readily observable characteristics (tool-making and language) are based on less easily observable mental processes that might be unique among humans: the ability to think symbolically, in the abstract or logically, although several species have demonstrated some abilities in these areas. Nor is it clear at what point exactly in human evolution these traits became prevalent. They are probably not restricted to the species Homo sapiens, seeing that the extinct species of the Homo genus (e.g. Homo neanderthalensis, Homo erectus) were also adept tool makers and may also have had linguistic skills.
The existence of other species that shape tools or use sign language may shed light on human evolution, but from the biological viewpoint the question "What single characteristic distinguishes humans from all other animals?" is peculiar: while superlatives are often also used for the description of other species (e. g. Whale, Cheetah, Hummingbird), the wish to find unique human characteristics is a matter of human self-reflection more than one of zoology.