<Tr> <Th> Categories: </Th> <Td> Births--Deaths Establishments--Disestablishments </Td> </Tr> <P> The 20th century was a century that began on January 1, 1901 and ended on December 31, 2000 . It was the tenth and final century of the 2nd millennium . It is distinct from the century known as the 1900s which began on January 1, 1900 and ended on December 31, 1999 . </P> <P> The 20th century was dominated by a chain of events that heralded significant changes in world history as to redefine the era: World War I and World War II, nuclear power and space exploration, nationalism and decolonization, the Cold War and post-Cold War conflicts; intergovernmental organizations and cultural homogenization through developments in emerging transportation and communications technology; poverty reduction and world population growth, awareness of environmental degradation, ecological extinction; and the birth of the Digital Revolution . It saw great advances in communication and medical technology that by the late 1980s allowed for near - instantaneous worldwide computer communication and genetic modification of life . </P> <P> Global total fertility rates, sea level rise and ecological collapses increased; the resulting competition for land and dwindling resources accelerated deforestation, water depletion, and the mass extinction of many of the world's species and decline in the population of others; consequences which are now being dealt with . It took all of human history up to 1804 for the world's population to reach 1 billion; world population reached an estimated 2 billion in 1927; by late 1999, the global population reached 6 billion . Global literacy averaged 80%; global lifespan - averages exceeded 40 + years for the first time in history, with over half achieving 70 + years (three decades longer than it was a century ago). </P>

Invention of the twentieth and twenty first centuries