The concept of extinction did not exist until the nineteenth century.
Until then there was no sense that species evolved, lived for a time,
and then went extinct. Because religion still held sway over so much of
the world, there was a sense that everything God had ever created would
still be found - somewhere. Even when large bones and shells of
creatures clearly unlike those familiar to the noted naturalists of the
day were uncovered from sedimentary strata, the belief was that the
creatures in question were still alive somewhere in the vast,
little-explored world. But by the early 1800s there was little of the
world still unexplored, and it fell to [url=http://www.ucmp.berkeley.edu/history/cuvier.html]Baron Georges Cuvier[/url]
(struggling to keep his head on his shoulders through the French
Revolution and its aftermath) to demonstrate the reality of extinction.
Cuvier, the so-called father of comparative anatomy, obtained the skull
and teeth of a proboscidean that was distinctly different from either
the African or the Indian elephant. He announced that the fossil
elephant parts came from a species now extinct.
[table:955e class="posting-table" border="0" align="left" cellspacing="0" width="215"] [tr] [td][img(215px,137px)]
http://www.astrobio.net/articles/images/lib/genetic.gif[/img][/td] [/tr] [tr:955e bordercolor="#000000" bgcolor="#ccccff"] [td:955e class="caption"]In
a eukaryote, the DNA is located in the nucleus of the cell. A DNA
molecule is composed of two helically spiral strands, each composed of
a linear chain of sugar and phosephate molecules. [i]Credit: MIT [/i][/td] [/tr] [/table]
Today, in a world where the extinction rate among endangered species is
occurring at an unknown but surely significant rate, it is pleasant to
think of a world without extinction and one so little explored that
even in the early 1900s Sir Arthur Conan Doyle could put his Lost World
with its diverse saurian legions atop a large plateau in the Amazon
region and readers could retain a sense of why not? Today we live in a
world that is the opposite. There is a sense that it holds no more
secrets, that the vast majority of its biota has been discovered and
cataloged, that even the immense oceans, now steadily giving up their
most famous wrecks to the Bob Ballards of the world, hold little
mystery. But this smugness that nature and its secrets are now
conquered might be a bit premature. Two recent events have made this
abundantly clear. First, in 2002, oceanographer Debbie Kelly of the
University of Washington (and another member of our astrobiology
faculty) made a startling discovery deep beneath the Atlantic Ocean.
Amid the mid-Atlantic Ridge, using submersibles and remote cameras,
Kelly and her crew found their own [url=http://www.washington.edu/newsroom/news/2000archive/12-00archive/k121200.html]Lost World[/url]
and named it the Lost City. They found the equivalent of the black
smokers [seen at Pacific Ocean hydrothermal vent sites], but this time
the substrate was white limestone rather than the darker peridotite
rock of the Pacific Ocean smoker systems.
The structures discovered are spectacular. Some are nearly two hundred
feet tall, growing like monstrous white stalactites up from the bottom
of the sea. These chimneys vent a diverse chemistry of fluids with
temperatures ranging from less than 40°C (104°F) to over 90°C (194°F).
The fluids coming out of the white chimneys are enriched in methane,
hydrogen, and hydrocarbons other than methane and are thus rich sources
of energy in form that can be utilized by life. And unlike the black
smokers of the Pacific, the microbes living among and in these white
chimneys are fueled by the chemistry of rock-altering reactions, not
simply the heat coming from deep earth. The Lost City hydrothermal
field is thus unlike any known submarine vent system and, according to
its discoverers, may be our closest analog to early Earth and early
Mars, on the basis of our understanding of the chemistry on those
planets at the beginning of their history. The temperatures are
moderate, the fluids have a high pH, and there are low metal
concentrations and high concentrations of energy sources. The Lost
City, which may be our best hope for finding a Lost World of early life
on earth, was unknown until 2002 and has been visited only once. There
is certainly an abundance of new microbes - and perhaps environments as
well - yet to be discovered there.
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