446 exploration: further reading America in two massive ice sheets The western ice sheet is called the American cordillera, and the eastern is called the Laurentia At certain times these two sheets met, and at other times a narrow corridor opened, stretching to Alberta, Canada, and there opening to the northern plains There is much disagreement still about whether it would have been possible to traverse what certainly would have been an inhospitable environment between massive glaciers While an inland route of exploration would have served a cold-adapted population best, it would not have been the only option available When the land bridge was submerged, prehistoric peoples could have walked across the ice pack in winter or paddled across in small boats in summer The Norwegian explorer and archaeologist Thor Heyerdahl, among others, has shown the extraordinary exploratory possibilities of seafaring among prehistoric peoples He established the feasibility of contact via an ocean crossing between South America and the South Pacific Archaeological evidence in Australia, Melanesia, and Japan indicate that boats were in use as far back as 25,000 to 40,000 years ago However, any signs of an exploratory route along the Pleistocene coastal shelf is now submerged; consequently, there is no direct archaeological evidence to support a Pacific coastal migration route It is also possible that populations crossed the 56 miles of the Bering Strait via boat when it was submerged and then continued south along the coast, a theory now growing in popularity Regardless of the route, highly mobile populations arrived and diff used as far as Patagonia in what appears to be an extremely abrupt period of time This area of investigation is still contested; few agree on when and where the earliest explorers and settlers arrived and under what conditions These hunter-gatherer societies slowly fi lled in the continents, eventually establishing sedentary or semisedentary patterns based on resource utilization By approximately 4000 b.c.e increased density and intensification of resource exploitation, characterized by pastoralism and agriculture, defined the period Few areas remained without human populations However, why some areas developed agriculture and domestication and some remained hunter-gatherer is still debated In South America, for example, during the Late Holocene (5,000 years ago to the present) the area from contemporary Venezuela and Colombia to central Chile and from the coast to the Andean cordillera was defined by agriculture and pastoralism, producing more than 80 percent of all food In Amazonia, the area including most of contemporary Brazil and the drainage of the Amazon, Orinoco, and Paraná river systems, between 20 percent and 80 percent of food was produced And in the southern portion, dominated by Patagonia, a hunter-gatherer system was maintained Similarly, between 4,000 and 6,000 years ago, back at the point after the original entrance into North America, the Inuit explored the top of the globe, pushing east as far as Greenland Subsequent cultural efflorescences and declines, and population expansions and contractions, from the standpoint of exploration, meant that people were continually on the move, populating new territory and sometimes repopulating previously occupied land Given the great amount of time that passed, these populations might have had no idea if they were the first to explore an area Increasingly sedentary civilizations led to development of ceremonial centers and ultimately to cultures with greater density and more complex social, political, and economic structures As civilizations advanced, exploration took on a different form, based in part on trade and exchange Likewise, as states grew and empires arose, exploration developed into a form related to war and conquest in the interest of securing and expanding borders, spreading state-supported religious ideals, and procuring objects or materials of significant value See also agriculture; art; astronomy; borders and frontiers; ceramics and pottery; cities; climate and geography; empires and dynasties; foreigners and barbarians; gender structure and roles; hunting, fishing, and gathering; language; literature; migration and population movements; military; nomadic and pastoral societies; roads and bridges; seafaring and navigation; settlement patterns; ships and shipbuilding; social collapse and abandonment; social organization; trade and exchange; war and conquest FURTHER READING M Cary and E H Warmington, The Ancient Explorers (Baltimore, Md.: Penguin Books, 1963) James C Chatters, Ancient Encounters: Kennewick Man and the First Americans (New York: Simon and Schuster, 2001) John Haywood, The Penguin Historical Atlas of Ancient Civilizations (New York: Penguin Group, 2005) Jona Lendering, “Hanno.” Livius: Articles on Ancient History Available online URL: http://www.livius.org/ha-hd/hanno/ hanno03.html Downloaded on January 9, 2007 R B Parkinson, The Tale of Sinuhe and Other Ancient Egyptian Poems: 1940–1640 B.C (Oxford U.K.: Griffith Institute, Ashmolean Museum, 1997) Heather Pringle, In Search of Ancient North America: An Archaeological Journey to Forgotten Cultures (New York: John Wiley and Sons, 1996) Duane W Roller, Through the Pillars of Herakles: Greco-Roman Exploration of the Atlantic (London: Routledge, 2006)