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In population biology and demography, generation time is the average time between two consecutive generations in the lineages of a population.In human populations, generation time typically has ranged from 20 to 30 years, with wide variation based on gender and society.
The first known mass extinction was the Great Oxidation Event 2.4 billion years ago, which killed most of the planet's obligate anaerobes. Researchers have identified five other major extinction events in Earth's history, with estimated losses below: [ 11 ]
An average modern life is around 85 years and consists of four periods of ~21 years Childhood → Young adult → Midlife → Elderhood; A generation is an aggregate of people born every ~21 years Baby Boomers → Gen X → Millennials → Homelanders; Each generation experiences "four turnings" every ~85 years
With the start of a new year on Jan. 1, 2025, comes the emergence of a new generation. 2025 marks the end of Generation Alpha and the start of Generation Beta, a cohort that will include all ...
The start and end of a new generation is sometimes vague, but these generation group names are often used for individuals born between the following years: Greatest Generation: 1901-1927 Silent ...
It also is "the average period, generally considered to be about 20–30 years, during which children are born and grow up, become adults, and begin to have children." [2] In kinship, generation is a structural term, designating the parent–child relationship. In biology, generation also means biogenesis, reproduction, and procreation.
of years ago) Life: 4,200 Archaea: ... where genes are mixed in every generation enabling greater variation for ... ranging up to 250 to 500 kya. [58] 160,000 years ...
The biosphere is postulated to have developed, from the origin of life onwards, at least some 3.5 billion years ago. [74] The earliest evidence for life on Earth includes biogenic graphite found in 3.7 billion-year-old metasedimentary rocks from Western Greenland [ 69 ] and microbial mat fossils found in 3.48 billion-year-old sandstone from ...