page_title: Abiogenesis
section_title: Spontaneous generation considered disproven in the 19th century
hierarchical_section_title: Abiogenesis / Conceptual history until the 1960s: biology / Spontaneous generation / Spontaneous generation considered disproven in the 19th century
caption_attribution_description: Charles Darwin. 1 negative&#160;: glass&#160;; 5 x 7 in. or smaller. From a photograph by Elliott &amp; Fry. According to Gene Kritsky, maintainer of an archive of Darwin photographs, this was from a photography session at Darwin's home, Down House, and on another photograph from that session Darwin wrote "1879" on the back. It was later widely sold and distributed on heavy card stock by Elliott &amp; Fry, with a caption dating it "Circa 1880". It was later reproduced in a wide range of Darwiniana.
context_page_description: In evolutionary biology, abiogenesis, or informally the origin of life, is the natural process by which life has arisen from non-living matter, such as simple organic compounds. While the details of this process are still unknown, the prevailing scientific hypothesis is that the transition from non-living to living entities was not a single event, but an evolutionary process of increasing complexity that involved molecular self-replication, self-assembly, autocatalysis, and the emergence of cell membranes. Although the occurrence of abiogenesis is uncontroversial among scientists, its possible mechanisms are poorly understood. There are several principles and hypotheses for how abiogenesis could have occurred.
  The study of abiogenesis aims to determine how pre-life chemical reactions gave rise to life under conditions strikingly different from those on Earth today. It primarily uses tools from biology, chemistry, and geophysics, with more recent approaches attempting a synthesis of all three: more specifically, astrobiology, biochemistry, biophysics, geochemistry, molecular biology, oceanography and paleontology.
context_section_description: By the middle of the 19th century, biogenesis had accumulated so much evidence in support that the alternative theory of spontaneous generation had been effectively disproven. Pasteur remarked, about a finding of his in 1864 which he considered definitive, 
  Never will the doctrine of spontaneous generation recover from the mortal blow struck by this simple experiment. 
  gave a mechanism by which life diversified from a few simple organisms to a variety of to complex forms. Today, scientists agree that all current life descends from earlier life, which has become progressively more complex and diverse through Charles Darwin's mechanism of evolution by natural selection.
  Darwin wrote to Hooker in 1863 stating that, 
  It is mere rubbish, thinking at present of the origin of life; one might as well think of the origin of matter.
   In On the Origin of Species, he had referred to life having been "created", by which he "really meant 'appeared' by some wholly unknown process", but had soon regretted using the Old Testament term "creation".
caption: Charles Darwin in 1879
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