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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 ...
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 ...
[15] [16] The Moon's gravitational pull stabilised Earth's fluctuating axis of rotation, setting up regular climatic conditions favoring abiogenesis. [17] 4404 Ma Evidence of the first liquid water on Earth which were found in the oldest known zircon crystals. [18] 4280–3770 Ma Earliest possible appearance of life on Earth. [19] [20] [21] [22]
1940. Overall life expectancy: 62.9 Women: 65.2 Men: 60.8 The United States began the ’40s on an upswing, with life expectancy up sharply from 58.5 years in 1936, when the nation was still ...
Published estimates for the 1st century ("AD 1") suggest uncertainty of the order of 50% (estimates range between 150 and 330 million). Some estimates extend their timeline into deep prehistory, to " 10,000 BC", i.e., the early Holocene, when world population estimates range roughly between 1 and 10 million (with an uncertainty of up to an ...
All life on Earth—including humanity—shares a last universal common ancestor (LUCA), [9] [10] [11] which lived approximately 3.5–3.8 billion years ago. [12] The fossil record includes a progression from early biogenic graphite [ 13 ] to microbial mat fossils [ 14 ] [ 15 ] [ 16 ] to fossilised multicellular organisms .
Life expectancy, more technically called the curtate expected lifetime and denoted ,[ a] is the mean of —that is to say, the expected number of whole years of life remaining, assuming survival to age . [ 149] So, (2) Substituting ( 1) into the sum and simplifying gives the final result [ 150]
This is especially true for Healthy life expectancy, the definition of which criteria may change over time, even within a country. For example, Canada is a country with a fairly high overall life expectancy at 81.63 years; however, this number decreases to 75.5 years for Indigenous people in the country. [4]