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Human
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] (http://www.pnas.org/cgi/content/abstract/99/21/13633).
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:
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
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