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.
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.