Human

**Humans**, or **modern humans** (***Homo sapiens*** or ***H. sapiens***), are the most common and widespread species of primate, and the only surviving species of the genus *Homo*. A great ape characterized by their hairlessness, bipedalism, and high intelligence, humans have large brains, enabling more advanced cognitive skills that enable them to thrive and adapt in varied environments, develop highly complex tools, and form complex social structures and civilizations. Humans are highly social, with individual humans tending to belong to a multi-layered network of cooperating, distinct, or even competing social groups -- from families and peer groups to corporations and political states. As such, social interactions between humans have established a wide variety of values, social norms, languages, and traditions (collectively termed institutions), each of which bolsters human society. Humans are also highly curious: the desire to understand and influence phenomena has motivated humanity's development of science, technology, philosophy, mythology, religion, and other frameworks of knowledge; humans also study themselves through such domains as anthropology, social science, history, psychology, and medicine. As of January 2024, there are more than 8 billion humans alive.

Early hominins--particularly the australopithecines, whose brains and anatomy are in many ways more similar to ancestral non-human apes—are less often referred to as "human" than hominins of the genus *Homo*. Several of these hominins used fire, occupied much of Eurasia, and the lineage that gave rise to *Homo sapiens* is thought to have diverged in Africa around 500,000 years ago, with the earliest fossil evidence of evidence of early *Homo sapiens* appearing (also in Africa) around 300,000 years ago. The oldest early *H. sapiens* fossils were found in Jebel Irhoud, Morocco dating to about 315,000 years ago. Omo-Kibish I (Omo I) from southern Ethiopia is the oldest anatomically modern Homo sapiens skeleton currently known (196 ± 5 ka). Humans began to exhibit evidence of behavioral modernity at least by about 100-70,000 years ago and (according to recent evidence) as far back as around 300,000 years ago, in the Middle Stone Age, (with some features of behavioral modernity possibly beginning earlier, and possibly in parallel with evolutionary brain globularization in *H. sapiens*). In several waves of migration, *H. sapiens* ventured out of Africa and populated most of the world.

The spread of the large and increasing population of humans has profoundly affected much of the biosphere and millions of species worldwide. Advantages that explain this evolutionary success include a larger brain with a well-developed neocortex, prefrontal cortex and temporal lobes, which enable advanced abstract reasoning, language, problem solving, sociality, and culture through social learning. Humans use tools more frequently and effectively than any other animal: they are the only extant species to build fires, cook food, clothe themselves, and create and use numerous other technologies and arts.

Humans uniquely use such systems of symbolic communication as language and art to express themselves and exchange ideas, and also organize themselves into purposeful groups. Humans create complex social structures composed of many cooperating and competing groups, from families and kinship networks to political states. Social interactions between humans have established an extremely wide variety of values, social norms, and rituals, which together undergird human society. Curiosity and the human desire to understand and influence the environment and to explain and manipulate phenomena (or events) have motivated humanity's development of science, philosophy, mythology, religion, and numerous other fields of knowledge.

Though most of human existence has been sustained by hunting and gathering in band societies, many human societies transitioned to sedentary agriculture approximately 10,000 years ago, domesticating plants and animals, thus enabling the growth of civilization. These human societies subsequently expanded, establishing various forms of government, religion, and culture around the world, and unifying people within regions to form states and empires. The rapid advancement of scientific and medical understanding in the 19th and 20th centuries permitted the development of fuel-driven technologies and increased lifespans, causing the human population to rise exponentially. The global human population was estimated to be near 7.8 billion in 2019.

## Etymology and Definition

In common usage, the word "human" generally refers to the only extant species of the genus *Homo*--anatomically and behaviorally modern *Homo sapiens*.

In scientific terms, the meanings of "hominid" and "hominin" have changed during the recent decades with advances in the discovery and study of the fossil ancestors of modern humans. The previously clear boundary between humans and apes has blurred, resulting in biologists now acknowledging the hominids as encompassing multiple species, and Homo and close relatives since the split from chimpanzees as the only hominins. There is also a distinction between *anatomically modern humans* and *Archaic Homo sapiens*, the earliest fossil members of the species.

The English adjective *human* is a Middle English loanword from Old French *humain*, ultimately from Latin *hūmānus*, the adjective form of *homō* "man." The word's use as a noun (with a plural: *humans*) dates to the 16th century. The native English term man can refer to the species generally (a synonym for *humanity*) as well as to human males, or individuals of either sex (though this latter form is less common in contemporary English).

The species binomial "*Homo sapiens*" was coined by Carl Linnaeus in his 18th-century work *Systema Naturae*. The generic name "*Homo*" is a learned 18th-century derivation from Latin *homō* "*man*," ultimately "*earthly being*" (Old Latin *hemō* a cognate to Old English *guma* "*man*," from PIE *dʰǵʰemon*-, meaning "*earth*" or "*ground*"). The species-name "*sapiens*" means "*wise*" or "*sapient*." Note that the Latin word *homo* refers to humans of either gender, and that "*sapiens*" is the singular form (while there is no such word as "*sapien*").

## History

### Evolution and Range

The genus Homo evolved and diverged from other hominins in Africa, after the human clade split from the chimpanzee lineage of the hominids (great apes) branch of the primates. Modern humans, defined as the species *Homo sapiens* or specifically to the single extant subspecies Homo sapiens sapiens, proceeded to colonize all the continents and larger islands, arriving in Eurasia 125,000-60,000 years ago, Australia around 40,000 years ago, the Americas around 15,000 years ago, and remote islands such as Hawaii, Easter Island, Madagascar, and New Zealand between the years 300 and 1280.

#### Evidence from Molecular Biology

The closest living relatives of humans are chimpanzees (genus *Pan*) and gorillas (genus *Gorilla*). With the sequencing of the human and chimpanzee genomes, current estimates of similarity between human and chimpanzee DNA sequences range between 95% and 99%. By using the technique called a molecular clock which estimates the time required for the number of divergent mutations to accumulate between two lineages, the approximate date for the split between lineages can be calculated. The gibbons (family *Hylobatidae*) and orangutans (genus *Pongo*) were the first groups to split from the line leading to the humans, then gorillas (genus *Gorilla*) followed by the chimpanzees (genus *Pan*). The splitting date between human and chimpanzee lineages is placed around 4–8 million years ago during the late Miocene epoch. During this split, chromosome 2 was formed from two other chromosomes, leaving humans with only 23 pairs of chromosomes, compared to 24 for the other apes.

#### Evidence from Fossil Record

There is little fossil evidence for the divergence of the gorilla, chimpanzee and hominin lineages. The earliest fossils that have been proposed as members of the hominin lineage are *Sahelanthropus tchadensis* dating from 7 million years ago, *Orrorin tugenensis* dating from 5.7 million years ago, and *Ardipithecus kadabba* dating to 5.6 million years ago. Each of these species has been argued to be a bipedal ancestor of later hominins, but all such claims are contested. It is also possible that any one of the three is an ancestor of another branch of African apes, or is an ancestor shared between hominins and other African Hominoidea (apes).