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The eponymous Silurians on Doctor Who are a race of reptilian humanoids from Earth's past, making their first appearance in the show in 1970. Frank and Schmidt cite Inherit the Stars, a 1977 novel by J. P. Hogan as containing a similar hypothesis, but also say they were surprised by how rarely the concept was explored in science fiction. [2]
The earliest of roots of science, which included medicine, can be traced to ancient Egypt and Mesopotamia in around 3000 to 1200 BCE. [11] [12] Their contributions shaped ancient Greek natural philosophy. [13] [11] [12] [14] [15] Ancient Greek philosophers such as Aristotle (384–322 BCE) contributed extensively to the development of ...
Life is a quality that distinguishes matter that has biological processes, such as signaling and self-sustaining processes, from matter that does not. It is defined descriptively by the capacity for homeostasis, organisation, metabolism, growth, adaptation, response to stimuli, and reproduction.
In biology, cell theory is a scientific theory first formulated in the mid-nineteenth century, that living organisms are made up of cells, that they are the basic structural/organizational unit of all organisms, and that all cells come from pre-existing cells.
The selection pressures that determine the reproductive strategy, and therefore much of the life history, of an organism can be understood in terms of r/K selection theory. The central trade-off to life history theory is the number of offspring vs. the timing of reproduction.
The hypothesis seeks to explain the apparent absence of extraterrestrial life despite its generally accepted plausibility and hence the reasonable expectation of its existence. [1] [2] Extraterrestrial life forms might, for example, choose to allow contact once the human species has passed certain technological, political, and/or ethical standards.
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An alternative—or complementary—theory of RNA origin is proposed in the PAH world hypothesis, whereby polycyclic aromatic hydrocarbons mediate the synthesis of RNA molecules. [106] PAHs are the most common and abundant of the known polyatomic molecules in the visible Universe and are a likely constituent of the primordial sea . [ 107 ]