Today humans have visited every bit of dry land in the world, and have colonized all but the most inaccessible and desolate regions. The human population now stands at about 6 billions.

HUMAN DIVERSITY
As humanity spread across the world, geographically separate groups of humans developed distinctive physical features. Scientists believe these features were adaptations to local environmental conditions such as temperature, elevation, diseases, and dietary resources. People of different racial origin often exhibit differences in blood groups and blood serum proteins, body size and build, dental characteristics, hair form and coverage, shape of face and facial features, and skin, hair, and eye colour. Although it took tens of thousands of years in relative isolation for these distinctive adaptations to emerge, modern lifestyles, technology, and mobility have almost eliminated their role in biological survival.

GLOBAL DIVISIONS
Important distinctions between people in different geographic areas still exist, however. No longer primarily based upon environmental conditions, modern groupings may be based on language, culture, nationality, religion, and economics. Geographers have found that the human world can be classified into groups at many different levels. The largest and most frequently used geographic groupings are called regions and states. States are easiest to define because they are based on the political boundaries of the world’s 190 or so nations. Some states have a clear geographic identity, being inhabited by people of similar racial and linguistic origin, all participating in a common economic and cultural system. In other cases, one state may include groupings of people with diverse backgrounds who operate within isolated social and economic environments.

Regions—which are sometimes difficult to depict accurately on maps—may be based on economic activity, climate and topography, cultural history, or location relative to other regions. One region may be defined in terms of the vast desert that dominates its landscape, whilst another may exist because its residents follow a common religion and speak one language, or be dependent on a single agricultural crop. Many regions cross national borders, but others exist entirely within a single state. Despite the difficulties in defining regions precisely, they are extremely useful to geographers because they are based on the meaningful social, cultural, and economic factors that produce a distinctive geographic identity.

RESOURCES AND ECONOMIES
The world contains a multitude of resources and commodities.