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Humans (Homo sapiens) are a species of
Great Ape and the only surviving species of the genus Homo. The species is commonly referred to as man,
mankind or humanity and its members as humans, human beings, persons or
people. Adult males are known as men and adult females as women. There is only one extant subspecies, H. sapiens sapiens. Humans are notable for their increased intelligence and the ability to use language.
Origins
Main article: Human evolution
The closest living evolutionary relatives to humans are the two species of
chimpanzee Pan
troglodytes ("common chimp") and Pan paniscus ("pygmy
chimp" or "Bonobo"), and to a lesser degree other hominoids such as orangutans and gorillas. It is important to
note however, that humans only share a common ancestor with these and are not descended directly from them. Biologists have
compared a sequence of DNA base pairs
between humans and chimpanzees, and estimated an overall genetic difference of 5% [1] . It has been estimated that the human lineage
diverged from that of chimpanzees about 5 million years ago, and from gorillas about 8 million years ago. However, recent news
reports of a hominid skull approximately 7 million years old already showing a divergence from the ape lineage strongly suggests
an earlier divergence. Some scientists argue that bonobos, chimpanzees and, possibly, gorillas should be lumped into the genus
Homo, but this is currently a minority opinion.
Various religious groups have raised objections and controversy concerning the theory of humanity's evolution from a common ancestor with the other hominoids. See
creationism and argument from evolution for opposing points of view.
Physical characteristics
The body of humans is described in the human anatomy group of articles. Humans have a wide range of variability in physical and other characteristics.
The evolution of Homo sapiens is characterized by a number of important trends:
- expansion of the brain cavity
and brain itself, which is typically about 1,400 cm³ in volume, well over twice that of a chimpanzee or gorilla. Some physical anthropologists argue that a reorganization of the structure of the brain is more
important than cranial expansion itself.
- canine tooth reduction.
- bipedal locomotion
- descent of the larynx (which makes possible the production of the complex sound
known as vocal language).
A human skeleton
How these trends are related, in what ways they have been adaptive, and what their role is in the evolution of complex social
organization and culture, are matters of ongoing debate among physical anthropologists.
Although body size is highly heritable, it is also significantly influenced by environmental and cultural factors such as diet. The mean height of an American adult female is 162 cm (64 in) and the mean weight is 62 kg (137 lb). Males are typically larger: 175 cm (69
in) and 78 kilograms (172 lb). Humans vary substantially around these means, and the means themselves have varied depending on
locality and historical factors.
Human children, typically weighing 3-4 kilograms (6-9 pounds) and 50-60 centimetres (20-24 inches) in height, are born after a
nine-month gestation period. Helpless at birth, they continue to grow for some
years, typically reaching sexual maturity at around 12-15 years of
age. Boys continue growing for some time after this, often only reaching their maximum height around the age of 18.
Human life expectancy at birth is approaching 80 years in wealthy
nations, with the assistance of science and technology, and it is thought that the maximum human life span
is about 120 years.
See also human physical appearance.
Mental characteristics
Humans consider themselves the most intellegent organism in the animal kingdom. Humans have the highest brain to bodymass ratio of all large animals (Dolphins have the second highest; Sharks have the highest for a fish). While this is not an absolute measure (inasmuch as a minimum brain-mass is necessary for
certain "housekeeping" functions), the brainmass to bodymass ratio does give a good indication of relative intelligence.
(Carl Sagan, The Dragons of Eden, 38)
The human ability to abstract is unparallelled in the animal kingdom. Tests have show that a full grown chimpanzee has
approximately the same ability to abstract as a four-year-old human child.
Pattern recognition is another area for which human beings
are mentally well-suited.
Thinking, IQ, Memory, Invention, Science, Philosophy, Knowledge, Education, Consciousness
Emotional characteristics
Emotion, Love, Hate, Happiness etc.
Spiritual characteristics
Religions maintain that, beyond having a physical and mental nature, mankind
also has a spiritual nature; many hold that this spiritual nature distinguishes mankind from other creatures. Most non-religious
maintain that mankind has no spiritual aspect, and is not thus distinguished.
Soul, Conscience, Religion, Morality, Prayer, Worship, etc.
The original habitat in which humans evolved is the African savannah (see
Vagina gentium, Environment of Evolutionary Adaptedness). Culturally transmitted technology
has allowed humans to colonize all of the continents and adapt to all climates.
Within the last few decades, humans have been able to temporarily inhabit Antarctica, the ocean depths, and outer space, although permanent habitation of these three environments is not yet
possible. Humans, with a population of about six billion, are one of the most numerous mammals on Earth.
Most humans (61%) live in the Asian region. The vast majority of the remainder live in
the Americas (14%), Africa (13%) and
Europe (12%), with only 0.3% in Australia. See list of countries by population and list of countries by population
density.
Being primates, humans' original life style is hunting/gathering, which is adapted to the savannah where they evolved. Other
human life styles are nomadism (often linked to animal herding) and permanent settlements
made possible by the development of agriculture. Humans have a great capacity for altering their habitats by various methods,
such as agriculture, irrigation, urban planning and construction, and activities accessory to those, such as transportation and manufacturing goods.
Permanent human settlements are dependent on proximity to water and, depending on the
lifestyle, other natural resources such as fertile land for growing crops and grazing
livestock or, seasonally by populations of prey. With the advent of large-scale trade and transportation infrastructure, immediate proximity to these
resources has become less necessary, and in many places these factors are no longer the driving force behind growth and decline
of population.
A sizable minority - around 2.5 of a total of 6.3 billion people - live in
urban surroundings. Urbanisation is
expected to rise drastically during the 21st century. Problems for humans
in cities include various forms of pollution, crime and poverty,
especially in inner city and suburban slums.
Humans living on Antarctica, under the ocean, or in space are part of scientific, military, or industrial expeditions, and
habitation of these environments is temporary.
Life in space has thus far been temporary living, with up to ten humans in space at a given time (seven on the Space Shuttle, three on Mir) and currently
around three in the International Space
Station. This is a direct result of humans' vulnerability to ionizing radiation. Prior to 1961, all humans were restricted to the earth; Yuri Gagarin was the first human to travel into space. At
various periods between 1969 and 1974, up to two humans spent varying amounts of time on the Moon. As of yet, residencies or human explorations on other planets have not
come to be.
Homo sapiens compared to other species
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
based in part on the Biblical Creation
story in which Adam is explicitly given dominion over the Earth and all of its
creatures.
Biologists and scientists in general, though, do not consider "dominant" to be a useful term, because the adaptive value of
any trait or complex of traits depends on the niche and is highly mutable. From a scientific standpoint, Homo sapiens
certainly is among the most generalized species on Earth. Smaller and simpler animals
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, for example, are adapted to specific environments,
whereas humans rely on the use of fire (see lifeform) and on tools such as clothing
and manufactured shelter, which are themselves often produced and used through
complex social interactions.
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 (building shelter, weaving fabrics
for clothing); the ability to alter the environment; language; and the development of complex social relationships and
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, though of
course no other animal uses tools to the same degree or with the same flexibility as Homo sapiens. 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.
Chomskian linguistics holds that a distinguishing feature of humans is that they are the only extant species with a
language instinct - a genetic predisposition that produces a
brain mechanism whose function is to acquire a language by observing those around us. Dolphins may also have this trait as they
show dialect.
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. That is, humans can think
abstractly about concepts and ideas. They can question, use logic, understand mathematical concepts, and so on in ways greater than other animals are known to do,
although several species have demonstrated some abilities in these areas. In any case, the idea that these abilities distinguish
humans from other species is the basis of the name Homo sapiens, sometimes translated as "Man the Thinker". It should be
noted, however, that the extinct species of the Homo genus (e.g. Homo neanderthalensis, Homo
erectus) were also adept tool makers and there is some evidence that they may have had linguistic skills.
While humans have all these characteristics, from the biological viewpoint the question "What single characteristic
distinguishes humans from all other animals?" is an odd one: it is not a question that is usually asked of cats, dolphins, or song sparrows. Finding other species that shape tools or can use sign language may shed light on human evolution, but it doesn't erase the differences or similarities between humans and other
species.
Human activity
See also
External link
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