Origins of Life On Earth
Further information: Evidence of common descent, Common descent, and Homology (biology)Biologists reason that all living organisms on Earth must share a single last universal ancestor, because it would be virtually impossible that two or more separate lineages could have independently developed the many complex biochemical mechanisms common to all living organisms. As previously mentioned the earliest organisms for which fossil evidence is available are bacteria, cells far too complex to have arisen directly from non-living materials. The lack of fossil or geochemical evidence for earlier organisms has left plenty of scope for hypotheses, which fall into two main groups: 1) that life arose spontaneously on Earth or 2) that it was "seeded" from elsewhere in the Universe.
Read more about this topic: Evolutionary History Of Life
Famous quotes containing the words origins of, origins, life and/or earth:
“The origins of clothing are not practical. They are mystical and erotic. The primitive man in the wolf-pelt was not keeping dry; he was saying: “Look what I killed. Aren’t I the best?””
—Katharine Hamnett (b. 1948)
“The settlement of America had its origins in the unsettlement of Europe. America came into existence when the European was already so distant from the ancient ideas and ways of his birthplace that the whole span of the Atlantic did not widen the gulf.”
—Lewis Mumford (1895–1990)
“All that a pacifist can undertake—but it is a very great deal—is to refuse to kill, injure or otherwise cause suffering to another human creature, and untiringly to order his life by the rule of love though others may be captured by hate.”
—Vera Brittain (1896–1970)
“Now listen, buddy, there are a few corny ideas you got to get out of your head if you’re going to fly an airplane. Most things are just the reverse from what people think. The higher you are the safer you are. The Earth down there, that, that’s your enemy because once you hit that, boy, you splatter.”
—Dalton Trumbo (1905–1976)