The Origin of Flight in Birds 题目： Debate over avian origins was stimulated in 1861 when the 150-million-year-old fossil of a bird-like creature was unearthed. Called Archaeopt...

  题目： Living-History Museums in the United States       The living-history approach to teaching social history combines restored or re-created historical ...

Dating Archaeological Objects     For contemporary archaeologists who need to know the age of any objects they study, perhaps the most precise and yet technologically ...

  Where Did the Carbon Go?     Over the last several hundred thousand years, atmospheric carbon dioxide (CO2) levels decreased when Earth's glacial ice sheets were ...

Animal Migration Patterns in the Serengeti   The Serengeti, a region in northern Tanzania, is the site of the largest mammal migration on Earth. Herds of wildebeest, zebras...

Indigo   题目： Indigo is a blue dye produced from plants of the genus group Indigofera, grown in tropical and subtropical climates, and it has been highly valued since ancie...

Early Photography in the United States     When photography first appeared in 1839 with the introduction of the daguerreotype, it was celebrated for revealing the truth ...

Igloos   In the language spoken by the Inuit-an indigenous people inhabiting the Arctic regions of Canada, Greenland, and the United States-the word 'igloo' means 'house' or '...

The Proto-Indo-European Language     Scholars have known for several centuries that most of the languages spoken in a broad swath from Britain to India are derived from ...

Wool Manufacturing in Europe in the High Middle Ages   During the High Middle Ages (1000-1300 c.E.), the Baltic Sea, North Sea, and English Channel tied together the peoples...