Geoscience Reference
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oceans, as the world's greatest concentrations of iron ores began to
settle on to the sea floors. Over time, this chemical and biological
evolution led to the myriad forms of life of the modern seas. These
organisms, from the tiniest microbe to the blue whale, share a single
point of origin.
The story of marine life is very largely the story of life on Earth
(Fig. 10). It is easy to forget, from our perspective—that of a late-
comer, landlubber species, living amid forests and meadows 72 —that
life on land in any practical sense is a late invention on this planet. The
invasion on to land took place less than half a billion years ago, while
the seas have teemed with living organisms for going on 4 billion
years. In understanding where we have come from it is, at heart, the
oceans that count.
Life Begins
In seventeenth-century Florence, the physician and naturalist Franc-
esco Redi turned his gaze towards decay and corruption, and discov-
ered one of the secrets of life. Redi undermined a central tenet of the
long-held view of the world, stemming from Aristotle, which held
that life could form spontaneously from lifeless matter. This idea had
been used to explain the appearance of maggots in rotting meat, mice
springing forth from hay, and even fossils as failed attempts at life.
Redi devised some simple but effective experiments to test for spon-
taneous generation, and these are among the first scientific experi-
ments that involved the use of a control. Redi took glass jars and
placed pieces of fish and meat into these: some of the jars he sealed
with muslin. Miraculously, maggots appeared in the open jars, but in
the jars that were sealed the contents remained free of infestation.
Redi surmised correctly that there were no maggots where flies were
unable to enter the jars. Redi, thus, may be regarded as the first true
experimental biologist. In his native Tuscany though, he is probably
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