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)
“Grown onto every inch of plate, except
Where the hinges let it move, were living things,
Barnacles, mussels, water weeds—and one
Blue bit of polished glass, glued there by time:
The origins of art.”
—Howard Moss (b. 1922)
“There is not any present moment that is unconnected with some future one. The life of every man is a continued chain of incidents, each link of which hangs upon the former. The transition from cause to effect, from event to event, is often carried on by secret steps, which our foresight cannot divine, and our sagacity is unable to trace. Evil may at some future period bring forth good; and good may bring forth evil, both equally unexpected.”
—Joseph Addison (1672–1719)
“It is in these acts called trivialities that the seeds of joy are forever wasted, until men and women look round with haggard faces at the devastation their own waste has made, and say, the earth bears no harvest of sweetness—calling their denial knowledge.”
—George Eliot [Mary Ann (or Marian)