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Arthur C. Clarke in 2001: A Space Odyssey (1968) has the claim that "Behind every man, now alive stand 30 ghosts, for that is the ratio by which the dead outnumber the living", which was roughly accurate at the time of writing. [9] [10] Recent estimates of the "total number of people who have ever lived" are in the order of 100 billion.
High, medium, and low projections of the future human world population [1] In world demographics, the world population is the total number of humans currently alive. It was estimated by the United Nations to have exceeded eight billion in mid-November 2022. It took around 300,000 years of human prehistory and history for the human population to ...
Human history. Human history is the record of humankind from prehistory to the present. Modern humans evolved in Africa around 300,000 years ago and initially lived as hunter-gatherers. They migrated out of Africa during the Last Ice Age and had populated most of the Earth by the end of the Ice Age 12,000 years ago.
The history of life on Earth traces the processes by which living and extinct organisms evolved, from the earliest emergence of life to the present day. Earth formed about 4.5 billion years ago (abbreviated as Ga, for gigaannum) and evidence suggests that life emerged prior to 3.7 Ga. [1] [2] [3] The similarities among all known present-day species indicate that they have diverged through the ...
The timeline of human evolution outlines the major events in the evolutionary lineage of the modern human species, Homo sapiens, throughout the history of life, beginning some 4 billion years ago down to recent evolution within H. sapiens during and since the Last Glacial Period. It includes brief explanations of the various taxonomic ranks in ...
World population milestones went unnoticed until the 20th century, since there was no reliable data on global population dynamics. [2] The population of the world reached. [3][4] Old estimates put the global population at 9 billion by 2037–2046, 14 years after 8 billion, and 10 billion by 2054–2071, 17 years after 9 billion; however these ...
The maximum life span, or oldest age a human can live, may be constant. [162] Further, there are many examples of people living significantly longer than the average life expectancy of their time period, such as Socrates (71), Saint Anthony the Great (105), Michelangelo (88), and John Adams (90). [162]
The history of Earth is divided into four great eons, starting 4,540 mya with the formation of the planet. Each eon saw the most significant changes in Earth's composition, climate and life. Each eon is subsequently divided into eras, which in turn are divided into periods, which are further divided into epochs. Eon.