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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 species indicate that they have diverged through the ...
The theory held that "lower" animals are generated by decaying organic substances. Aristotle stated that, for example, aphids arise from dew on plants, flies from putrid matter, mice from dirty hay, and crocodiles from rotting sunken logs. [16] The basic idea was that life was continuously created as a result of chance events. [17]
However, viruses are still poorly understood and may have arisen before "life" itself, or may be a more recent phenomenon. Major extinctions in terrestrial vertebrates and large amphibians. Earliest examples of armoured dinosaurs. 195 Ma First pterosaurs with specialized feeding (Dorygnathus). First sauropod dinosaurs.
“How did life begin?” is one of the most profound scientific questions ever pondered. And it makes sense that such a grand idea would inspire many possible theories and explanations—both ...
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 spread across Earth's continental land except Antarctica by the end of the Ice Age 12,000 years ago.
Darwin did not publish his ideas on evolution for 20 years. However, he did share them with certain other naturalists and friends, starting with Joseph Dalton Hooker, with whom he discussed his unpublished 1844 essay on natural selection. During this period he used the time he could spare from his other scientific work to slowly refine his ...
The deep sea or alkaline hydrothermal vent theory posits that life began at submarine hydrothermal vents. [ 218 ] [ 219 ] William Martin and Michael Russell have suggested "that life evolved in structured iron monosulphide precipitates in a seepage site hydrothermal mound at a redox, pH, and temperature gradient between sulphide-rich ...
Despite the deprivations, Grateful Life beat jail and it gave addicts time to think. Many took the place and its staff as inspiration. They spent their nights filling notebooks with diary entries, essays on passages from the Big Book, drawings of skulls and heroin-is-the-devil poetry.