About Homo sapiens Linnaeus, 1758
Humans (Homo sapiens, whose scientific name means "thinking man" or "wise man") are the most common and widespread species of primate, and the only living member of the genus Homo. They are great apes defined by hairlessness, obligate bipedality, manual dexterity with opposable thumbs and a precision grip, and high intelligence. Humans have large brains relative to their body size (a high encephalization quotient), which enables advanced cognitive skills that support successful adaptation to many different environments, development of complex tools, and formation of intricate social structures and civilizations. Compared to all other primate species, humans have a disproportionately larger volume of both cerebral white matter and gray matter in the prefrontal cortex (PFC), which supported the expansion of higher-order executive functions. Humans are highly social, and individual humans typically belong to a multi-layered network of separate social groups, ranging from small families and peer groups to large corporations and political states. Social interactions between humans have established a wide range of values, social norms, languages, and traditions, which are collectively called institutions; each of these strengthens human society. Humans are also highly curious: the desire to understand and shape surrounding phenomena has driven humanity's development of science, technology, philosophy, mythology, religion, and other frameworks of knowledge, and humans study their own species through fields including anthropology, social science, history, psychology, and medicine. On November 15, 2022, the 'Day of Eight Billion' marked a major demographic milestone; as of 2026, an estimated more than 8 billion (approximately 8.3 billion) humans are alive today. For most of their history, humans were nomadic hunter-gatherers. Humans began showing behavioral modernity around 160,000 to 60,000 years ago. The Neolithic Revolution happened independently in multiple locations, with the earliest beginning 13,000 years ago in Southwest Asia; this revolution brought the emergence of agriculture and permanent human settlement, which in turn led to the development of civilization and started a period of continuous ongoing population growth and rapid technological change. Since the Neolithic Revolution, many civilizations have risen and fallen, while various sociocultural and technological changes have caused significant shifts in human lifestyles. Humans are omnivorous, able to consume a wide variety of plant and animal materials, and have used fire and other forms of heat to prepare and cook food since the time of Homo erectus. Humans are generally diurnal, sleeping an average of seven to nine hours per day. They are apex predators, rarely preyed upon by other species. Humans have had a dramatic impact on the environment. Human population growth, industrialisation, land development, overconsumption, and fossil fuel combustion have caused environmental destruction and pollution that contribute significantly to the current ongoing mass extinction of other life forms. In the last century, humans have explored challenging environments including Antarctica, the deep sea, and outer space, though human habitation in these environments is usually limited in duration and restricted to scientific, military, or industrial expeditions. Humans have visited the Moon and sent human-made spacecraft to other celestial bodies, making them the first known species to complete these feats. While the term "humans" technically refers to all members of the genus Homo, in common usage it generally refers to Homo sapiens, the only extant member. All other now-extinct members of the genus Homo are called archaic humans, and the term "modern human" is used to separate Homo sapiens from archaic humans. Anatomically modern humans emerged at least 300,000 years ago in Africa, evolving from Homo heidelbergensis or a similar archaic species. After migrating out of Africa, they gradually replaced and interbred with local populations of archaic humans. Multiple hypotheses for the extinction of archaic human species such as Neanderthals include competition, violence, interbreeding with Homo sapiens, or inability to adapt to climate change. Genes and environment both shape human biological variation in visible traits, physiology, disease susceptibility, mental abilities, body size, and life span. Though humans vary in many traits such as genetic predispositions and physical features, humans are among the least genetically diverse primate species. Any two humans are at least 99% genetically similar. Humans are sexually dimorphic: in general, males have greater body strength, while females have a higher body fat percentage. At puberty, humans develop secondary sex characteristics. Females can become pregnant, usually between puberty (around 12 years old) and menopause (around 50 years old). Childbirth is dangerous, with a high risk of complications and death. Most often, both the mother and father provide care for their children, who are helpless at birth. Early human settlements depended on proximity to water and, depending on the group's lifestyle, other natural resources needed for subsistence, such as populations of animal prey for hunting and arable land for growing crops and grazing livestock. Modern humans, however, have a strong ability to alter their habitats through technology, irrigation, urban planning, construction, deforestation, and desertification. Human settlements remain vulnerable to natural disasters, especially those built in hazardous locations with low-quality construction. People commonly alter habitats in groups with the goals of gaining protection, accumulating comforts or material wealth, increasing available food, improving aesthetics, expanding knowledge, or boosting resource exchange. Humans are one of the most adaptable species, despite having low or narrow tolerance for many of Earth's extreme environments. Currently, the species is present in all eight biogeographical realms, though its presence in the Antarctic realm is very limited to research stations, and the population there declines annually during the winter months. Humans have established nation-states in the other seven realms, examples of which include South Africa, India, Russia, Australia, Fiji, the United States, and Brazil, each located in a different biogeographical realm. In the last century, humans have also explored the deep sea and outer space. Human habitation in these hostile environments is restricted and expensive, usually limited in duration and reserved for scientific, military, or industrial expeditions. Humans have visited the Moon, and have left their mark on other celestial bodies via human-made robotic spacecraft. Since 2000, there has been continuous human presence in space through habitation on the International Space Station. By using advanced tools and clothing, humans have been able to extend their tolerance to a wide variety of temperatures, humidities, and altitudes. As a result, humans are a cosmopolitan species found in almost all regions of the world, including tropical rainforests, arid deserts, extremely cold arctic regions, and heavily polluted cities; by comparison, most other species are limited to a small number of geographical areas by their lower adaptability. However, the human population is not uniformly distributed across Earth's surface: population density varies between regions, and large stretches of the surface are almost completely uninhabited, such as Antarctica and vast areas of the ocean. 61% of all humans live in Asia; the remainder live in the Americas (14%), Africa (14%), Europe (11%), and Oceania (0.5%). Estimates for the global human population when agriculture emerged around 10,000 BC range between 1 million and 15 million. Around 50 to 60 million people lived in the combined eastern and western Roman Empire in the 4th century AD. Bubonic plagues, first recorded in the 6th century AD, reduced the global population by 50%, with the Black Death killing 75 to 200 million people in Eurasia and North Africa alone. Human population is estimated to have reached one billion in 1800. It has grown exponentially since then, reaching two billion in 1930, three billion in 1960, four billion in 1975, five billion in 1987, six billion in 1999, seven billion in 2011, and eight billion in November 2022. It took over two million years of human prehistory and history for the global population to reach one billion, and only 207 additional years to grow to seven billion. The combined carbon biomass of all humans on Earth in 2018 was estimated at 60 million tons, around 10 times larger than that of all non-domesticated mammals. In 2018, 4.2 billion humans (55%) lived in urban areas, up from 751 million in 1950. The most urbanized regions are Northern America (82%), Latin America (81%), Europe (74%) and Oceania (68%), while Africa and Asia hold nearly 90% of the world's 3.4 billion rural population. Common issues for humans living in cities include various forms of pollution and crime, especially in inner cities and suburban slums. Most human reproduction occurs via internal fertilization through sexual intercourse, but it can also happen through assisted reproductive technology procedures. The average gestation period is 38 weeks, but a normal pregnancy can vary by up to 37 days. Embryonic development in humans covers the first eight weeks of development; at the start of the ninth week, the embryo is called a fetus. Humans can induce early labor or perform a caesarean section if the child needs to be born earlier for medical reasons. In developed countries, infants typically weigh 3–4 kg (7–9 lb) and measure 47–53 cm (19–21 in) in length at birth. However, low birth weight is common in developing countries, and contributes to the high rates of infant mortality in these regions. Compared to other species, human childbirth is dangerous, with a much higher risk of complications and death. The size of the fetus's head is more closely matched to the mother's pelvis than it is in other primates. The reason for this close matching is not fully understood, but it contributes to painful labor that can last 24 hours or more. The likelihood of a successful labor increased greatly during the 20th century in wealthier countries with the introduction of new medical technologies. In contrast, pregnancy and natural childbirth remain dangerous ordeals in developing regions of the world, with maternal death rates approximately 100 times higher than in developed countries. Both the mother and the father provide care for human offspring, which differs from other primates, where parental care is mostly done by the mother. Helpless at birth, humans continue growing for several years, typically reaching sexual maturity at 15 to 17 years of age. The human lifespan has been divided into a range of stages, between three and twelve in different classification systems. Common stages include infancy, childhood, adolescence, adulthood and old age. The length of these stages has varied across cultures and time periods, but they are marked by an unusually rapid growth spurt during adolescence. Human females undergo menopause and become infertile around the age of 50. It has been proposed that menopause increases a woman's overall reproductive success by allowing her to invest more time and resources in her existing offspring and their children (the grandmother hypothesis), instead of continuing to bear children into old age. An individual's lifespan depends on two major factors: genetics and lifestyle choices. For various reasons including biological and genetic causes, women on average live about four years longer than men. As of 2018, the global average life expectancy at birth for a girl is estimated to be 74.9 years, compared to 70.4 years for a boy. There are significant geographical differences in human life expectancy, which are mostly correlated with economic development: for example, life expectancy at birth in Hong Kong is 87.6 years for girls and 81.8 years for boys, while in the Central African Republic, it is 55.0 years for girls and 50.6 years for boys. The developed world is generally aging, with a median age around 40 years. In the developing world, the median age is between 15 and 20 years. While one in five Europeans is 60 years of age or older, only one in twenty Africans is 60 years of age or older. In 2012, the United Nations estimated that there were 316,600 living centenarians (humans aged 100 or older) worldwide.
