The image is of a seagull, a member of the animal kingdom.
The Origin of Life on Earth
How did it all begin? Perhaps the most intriguing question we, as human
beings, could ever contemplate is that of our own origin.
At least three classes of hypotheses exist attempting to explain the
origin of life on Earth
. The first, and
oldest of these suggest that life was created by a supreme being or
spiritual force. These ideas and explanations have been passed
down from generation to generation and vary considerably among different
cultures and religions. Because theories about creation can neither be
proved nor disproved, they lie outside the realm of science and will not
be pursued further in these pages. We leave it to each individual to
decide for him- or herself.
The second set of hypotheses suggest that life began elsewhere in the
universe and "arrived" on Earth by chance, such as with the crash of a comet
The third, and most widely held hypothesis in the scientific community,
is that life on Earth arose approximately 3.5 - 4 billion years ago as the
of a very specific sequence of random chemical events. This theory
suggests that the early environment of Earth may have provided the
appropriate conditions for the spontaneous formation of organic
molecules--the building blocks of life. In the early 1950's two
biochemists, Stanley Miller and Harold Urey, conducted an experiment
which demonstrated the
spontaneous formation of amino acids from inorganic precursors in the lab.
It is assumed that over time, the early organic molecules interacted,
eventually leading to the evolution of the
first life forms
Shop Windows to the Universe Science Store!
"Science, Evolution, and Creationism
", by the National Academies, provides fascinating background on these topics for all, and is particularly useful for the Earth and space science classroom. Check our other books
in our online store
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