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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 basic idea was that life was continuously created as a result of chance events. [17] In the 17th century, people began to question spontaneous generation, in works like Thomas Browne's Pseudodoxia Epidemica. His contemporary, Alexander Ross, erroneously rebutted him. [18] [19] In 1665, Robert Hooke published the first drawings of a ...
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.
NASA's 2015 strategy for astrobiology aimed to solve the puzzle of the origin of life – how a fully functioning living system could emerge from non-living components – through research on the prebiotic origin of life's chemicals, both in space and on planets, as well as the functioning of early biomolecules to catalyse reactions and support inheritance.
12-8 Ma The clade currently represented by humans and the genus Pan (chimpanzees and bonobos) splits from the ancestors of the gorillas between c. 12 to 8 Ma. [31] 8-6 Ma Sahelanthropus tchadensis. Hominini: The latest common ancestor of humans and chimpanzees is estimated to have lived between roughly 10 to 5 million years ago.
Evolutionary thought, the recognition that species change over time and the perceived understanding of how such processes work, has roots in antiquity. With the beginnings of modern biological taxonomy in the late 17th century, two opposed ideas influenced Western biological thinking: essentialism, the belief that every species has essential characteristics that are unalterable, a concept ...
As for life on land, in 2019 scientists reported the discovery of a fossilized fungus, named Ourasphaira giraldae, in the Canadian Arctic, that may have grown on land a billion years ago, well before plants are thought to have been living on land. [100] [101] [102] The earliest life on land may have been bacteria 3.22 billion years ago. [103]
Gradually, life expands to land and familiar forms of plants, animals and fungi begin appearing, including annelids, insects and reptiles, hence the eon's name, which means "visible life". Several mass extinctions occur, among which birds, the descendants of non-avian dinosaurs, and more recently mammals emerge.