Changes

== Habitat and population ==

== Habitat and population ==

Early human settlements were dependent on proximity to [[water resources|water]] and, depending on the lifestyle, other natural resources, such as fertile land for growing crops and grazing [[livestock]], or seasonally by [[hunting]] populations of prey. However, humans have a great capacity for altering their [[habitat (ecology)|habitats]] by various methods, such as through [[irrigation]], [[urban planning]], [[construction]], [[transport]], and [[manufacturing]] goods. With the advent of large-scale trade and transport infrastructure, proximity to these resources has become unnecessary, and in many places these factors are no longer a driving force behind the growth and decline of a population. Nonetheless, the manner in which a habitat is altered is often a major determinant in population change.

Early human settlements were dependent on proximity to [[water resources|water]] and, depending on the lifestyle, other natural resources, such as fertile land for growing crops and grazing [[livestock]], or seasonally by [[hunting]] populations of prey. However, humans have a great capacity for altering their [[habitat (ecology)|habitats]] by various methods, such as through [[irrigation]], [[urban planning]], [[construction]], [[transport]], and [[manufacturing]] goods. With the advent of large-scale trade and transport infrastructure, proximity to these resources has become unnecessary, and in many places these factors are no longer a driving force behind the growth and decline of a population. Nonetheless, the manner in which a habitat is altered is often a major determinant in population change.

Human habitation within [[closed ecological system]]s in hostile environments, such as Antarctica and outer space, is expensive, typically limited in duration, and restricted to scientific, military, or industrial expeditions. Life in space has been very sporadic, with no more than thirteen humans in space at any given time. Between 1969 and 1972, two humans at a time spent brief intervals on the [[exploration of the Moon|Moon]]. [[As of 2007]], no other celestial body has been visited by human beings, although there has been a continuous human presence in outer space since the launch of the initial crew to inhabit the [[International Space Station]] on [[October 31]], [[2000]]; however, humans have made [[robot]]s that have visited other celestial bodies.

Human habitation within [[closed ecological system]]s in hostile environments, such as Antarctica and outer space, is expensive, typically limited in duration, and restricted to scientific, military, or industrial expeditions. Life in space has been very sporadic, with no more than thirteen humans in space at any given time. Between 1969 and 1972, two humans at a time spent brief intervals on the [[exploration of the Moon|Moon]]. [[As of 2007]], no other celestial body has been visited by human beings, although there has been a continuous human presence in outer space since the launch of the initial crew to inhabit the [[International Space Station]] on [[October 31]], [[2000]]; however, humans have made [[robot]]s that have visited other celestial bodies.

From AD 1800 to 2000, the human population increased from one billion to six billion. In 2004, around 2.5 billion out of 6.3 billion people (39.7%) lived in [[urban area]]s, and this percentage is expected to rise throughout the 21st century. Problems for humans living in [[city|cities]] include various forms of [[pollution]] and [[crime]],<ref>[http://www.ojp.usdoj.gov/bjs/abstract/usrv98.htm Urban, Suburban, and Rural Victimization, 1993-98] U.S. Department of Justice, Bureau of Justice Statistics,. Accessed 29 Oct 2006</ref> especially in inner city and suburban slums. Benefits of urban living include increased literacy, access to the global canon of human knowledge and decreased susceptibility to rural [[famines]].

From AD 1800 to 2000, the human population increased from one billion to six billion. In 2004, around 2.5 billion out of 6.3 billion people (39.7%) lived in [[urban area]]s, and this percentage is expected to rise throughout the 21st century. Problems for humans living in [[city|cities]] include various forms of [[pollution]] and [[crime]],[http://www.ojp.usdoj.gov/bjs/abstract/usrv98.htm] especially in inner city and suburban slums. Benefits of urban living include increased literacy, access to the global canon of human knowledge and decreased susceptibility to rural [[famines]].

Humans have had a dramatic effect on the [[natural environment|environment]]. It has been hypothesized that in the past, human predation has contributed to the extinction of a number of species; as humans are not generally preyed on themselves, humans have been described as the ultimate [[apex predator|superpredators]].<ref>''[[Scientific American]]'' (1998). [http://www.csulb.edu/~kmacd/346IQ.html Evolution and General Intelligence: Three hypotheses on the evolution of general intelligence].</ref> Currently, through land development and [[pollution]], humans are thought to be the main contributor to global [[climate change]].<ref>{{cite web|url=http://www.grida.no/climate/ipcc_tar/wg1/007.htm|title=www.grida.no/climate/ipcc_tar/wg1/007.htm<!-- INSERT TITLE -->|accessdate=2007-05-30}}</ref> This is believed to be a major contributor to the ongoing [[Holocene extinction event]], a [[extinction event|mass extinction]] which, if it continues at its current rate, is predicted to wipe out half of all species over the next century.<ref>[[American Association for the Advancement of Science]]. [http://atlas.aaas.org/index.php?sub=foreword Foreword]. ''AAAS Atlas of Population & Environment''.</ref><ref>[[E. O. Wilson|Wilson, E.O.]] (2002). ''in The Future of Life''.</ref>

Humans have had a dramatic effect on the [[natural environment|environment]]. It has been hypothesized that in the past, human predation has contributed to the extinction of a number of species; as humans are not generally preyed on themselves, humans have been described as the ultimate [[apex predator|superpredators]].'[[Scientific American]]'' [http://www.csulb.edu/~kmacd/346IQ.html Evolution and General Intelligence: Three hypotheses on the evolution of general intelligence]. Currently, through land development and [[pollution]], humans are thought to be the main contributor to global [[climate change]]. [http://www.grida.no/climate/ipcc_tar/wg1/007.htm] This is believed to be a major contributor to the ongoing [[Holocene extinction event]], a [[extinction event|mass extinction]] which, if it continues at its current rate, is predicted to wipe out half of all species over the next century.<ref>[[American Association for the Advancement of Science]]. [http://atlas.aaas.org/index.php?sub=foreword Foreword]. ''AAAS Atlas of Population & Environment''. [[E. O. Wilson|Wilson, E.O.]] (2002). ''in The Future of Life''.</ref>

== Biology ==

== Biology ==