Life consists of reproduction with (heritable) variations. NASA defines life as "a self-sustaining chemical … See more

One ancient view of the origin of life, from Aristotle until the 19th century, is of spontaneous generation. This theory held that "lower" animals were generated by decaying organic substances, and that life arose by ch… See more

Soon after the Big Bang, which occurred roughly 14 Gya, the only chemical elements present in the universe were hydrogen, helium, and lithium, the three lightest atoms in the periodic table. These elements gradually a… See more

All chemical elements except for hydrogen and helium derive from stellar nucleosynthesis. The basic chemical ingredients of life – the carbon-hydrogen molecule (CH), the carbon-hydrogen positive io… See more

The largest unanswered question in evolution is how simple protocells first arose and differed in reproductive contribution to the following generation, thus initiating the evolution of life. The lipid world theory … See more

Life requires a loss of entropy, or disorder, when molecules organize themselves into living matter. The emergence of life and increased complexity does not contradict the second law of thermodynamics, which states that … See more

A variety of geologic and environmental settings have been proposed for an origin of life. These theories are often in competition with one another as there are many differing views of prebiotic compound availability, … See more