Worms are older than you think

[Larry Dunn <majestic_cheese@yahoo.com>]

Sorry about off-topicality of this, but it's interesting!

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Worm-Like Animals Found in Old Rock

Filed at 3:42 p.m. EDT

By The Associated Press
WASHINGTON (AP) -- Complex animals may have evolved far earlier in
Earth's history than previously believed, according to researchers who
say tiny tunnels preserved in rock in India were dug by burrowing,
worm-like creatures more than a billion years ago. 

The tunnels, about the size of a soda straw, are thought to be the
oldest trace fossil ever found and probably were carved by a worms
that lived under the muck at the bottom of a shallow sea, Adolph
Seilacher of Yale University said Wednesday. 

A report on the study is to be published Friday in the journal
Science. Multicellular animals made a dramatic appearance in the
fossil record about 540 million years ago at the beginning of what is
called the Cambrian period. Animals then developed skeletons, shells
and mineralized bodies that were preserved in the fossils. 

Before that, it has been believed, life consisted of primitive,
soft-bodied organism that left no trace in the fossil record.
Scientists generally believed that life started some 4 billion years
ago with simple, single-celled creatures that crept slowly up the
evolutionary ladder until there an explosion of new, complex life
forms during the Cambrian. 

But Seilacher, a professor emeritus at the University of Tubingen in
Germany, said that discovery of the worm tunnels in India shows that
there were multicellular animals, with complicated and intricate 
lifestyles, more than a half-billion years before the Cambrian. 

``This means that the birth of multicellular animals was at least
twice as long ago as we thought,'' he said. ``It means that animals
have a much longer history that we once believed.'' 

The announcement, made at a German news conference, met with immediate
skepticism among some paleontologist. (sic)

``It this were true, it would be very important,'' said Bruce
Runnegar, a UCLA paleontologist. ``I would like to see evidence for
animals 1 billion years old. But I don't think this discovery
represents the 
final, unequivocal proof.'' Seilacher and his colleagues found the
tunnels, now eroded to mere meandering grooves, in sandstone in
northern India. 
The rock was formed from sand that once was the floor of a shallow sea. 

Seilacher said he believes the worm-like creatures lived in the sand
and fed on a mat of decaying organic matter that coatedthe sea floor.
The organic matter, he said, probably was the bodies of microorganisms
and 
algae that lived in the water, died and sank to the bottom. 

Seilacher said the path of the tunnels seem to purposely follow the
contours of the sea floor, as if the animals were feeding from below
on the organic debris. Some of the tunnels have branches, he said, 
suggesting that the animals sometimes dug forward andthen backed out
to take a new burrowing path. This, he said, suggests a complex life
form that had
nerves, instincts and senses. 

The shape of the tunnels, said Seilacher, suggests the animals moved
by a wavelike action and could have been coated with amucous that
eased the passage through the sand. Seilacher said the sand containing
the tunnels
hardened over time to become rock and this preserved the impressions
of the tunnels. In recent geologic times, the rock has been lifted up
and layers eroded away, revealing the tunnels as grooves in the soft
stone. 

Runnegar said a troubling element of Seilacher's conclusion is that
there is a 400 million-year gap in the fossil record between the worm
tunnels and the hard-bodied fossils of animals from the Cambrian
period. 

``If these animals had evolved (1 billion years ago),one would expect
to see many similar tunnels in sedimentary rocks between that period
and the Cambrian explosion,'' he said. ``Why don't we find lots of
these tunnels?'' 

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==
Larry

"I've been ionized, but I'm okay now." 

http://members.tripod.com/~megalania/index.html

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