I'll start with a quote:
"From unicellular organisms to man, all cells have a (UV) repair system.
This is no surprise after all, life emerged under the sun. It may appear
strange that the repair system should be active even in cells that
have never been exposed to radiation, like the cells of the bowels..."
(Unraveling DNA, Frank-Kamenetskii)

Since the repair system in the bowel cells are active, according

On the other hand, if they do have UV repair systems,
then it seems logical that they were exposed to
UV first and only evolved to vent life after.

The "UV first" statement doesn't seem logical at all.

On the other hand, if they do have UV repair systems,
then it seems logical that they were exposed to
UV first and only evolved to vent life after.

The "UV first" statement doesn't seem logical at all.
1) If life evolved in a vent system niche, a few pioneers would
have had to to venture into the rest of the world for us to be here.
2) The pioneers who ventured to the surface and near surface
would have evolved UV repair mechanisms.
3) Once established in a UV environment, the descendents of those
pioneers have a high probability of recolonizing the deep vents. Some
of these recolonized creatures would evolve degenerate UV repair
mechanisms, or lose all trace of their UV repair mechanisms. Therefore,
at least a few of the extant deep vent creatures probably have eith no
or degenerate remains of a UV repair mechnism, whether or not life
evolved in the vents.

Surfacists - What about eyeless cave creatures?
A good analogy would to your hypothesis would be blind cave life.
Since early life probably didn't have eyes, early life was probably
didn't have eyes. Some species of cave life don't have eyes. It doesn't
follow that all life evolved in a cave environment. Alternatively, the
fact that most cave creatures have degenerate eyes doesn't imply that
all life evolved in sunlight.

But how about some facts - who knows if vent tube worms and bacteria
and all the rest have the UV repair mechanisms that surface life does,
(and like the other poster said -
is it strickly UV repair - that is pyrimidine dimer repair).
Also again I ask - are there URACIL dimers - if so does UV often
damage tRNA? I've never heard anything about it.

Thinking about the chemistry for a minute, rather than the

Ventists,
Here's a possible clue to helping your OOL scenario.
I'll start with a quote:
"From unicellular organisms to man, all cells have a (UV) repair system.
This is no surprise after all, life emerged under the sun. It may appear
strange that the repair system should be active even in cells that
have never been exposed to radiation, like the cells of the bowels..."
(Unraveling DNA, Frank-Kamenetskii)

IF life began from vents and was not a reaction to the energy of the
sun/heat cycle, it would seem natural that vent life should
NOT have UV repair systems. They would never be exposed to the UV,
so why evolve to UV repair when its never needed.
On the other hand, if they do have UV repair systems,
then it seems logical that they were exposed to
UV first and only evolved to vent life after.

Comments on the UV Repair test for OOL scenarios?


Tom Hendricks
Paper on UV/Origin of Life
http://www.daviddarling.info/encyclopedia/U/UV_origin_of_life.html

Tom,

I am not a "ventist", although I am open to the idea. The problem with
your criticism is that our current vent communities are not the descendants
of any primordial vent organisms. They have colonized the vents in recent
times from surface dwelling ancestors, who would have benefited from UV
protection. Earlier vent organisms, including the original vent lineages if
that is where life originated, went extinct a very long time ago.

Guy

I am not a "ventist", although I am open to the idea. The problem with
your criticism is that our current vent communities are not the descendants
of any primordial vent organisms. They have colonized the vents in recent
times from surface dwelling ancestors, who would have benefited from UV
protection. Earlier vent organisms, including the original vent lineages if
that is where life originated, went extinct a very long time ago.

Guy A Hoelzer wrote:
Tom,

I am not a "ventist", although I am open to the idea. The problem with
your criticism is that our current vent communities are not the descendants
of any primordial vent organisms. They have colonized the vents in recent
times from surface dwelling ancestors, who would have benefited from UV
protection. Earlier vent organisms, including the original vent lineages if
that is where life originated, went extinct a very long time ago.

Guy

Is that your opinion or is it based on confirmed studies? If studies
can you list one?

Guy A Hoelzer wrote:

I am not a "ventist", although I am open to the idea. The problem with
your criticism is that our current vent communities are not the descendants
of any primordial vent organisms. They have colonized the vents in recent
times from surface dwelling ancestors, who would have benefited from UV
protection. Earlier vent organisms, including the original vent lineages if
that is where life originated, went extinct a very long time ago.

While a possibility - and certainly true for many of the
animals involved - is there any evidence that the extremophile
bacteria at the root of these food webs ever lived anywhere
else apart from ecosystems like these vents?

Evidence that they were especially insensitive to UV light
at frequencies emitted from by sun would qualify as such
evidence - but as far as I know, nothing like that has been
found so far.

IMO, their ancestors probably /did/ live elsewhere a
long time ago - before the LCA of life on earth lived.

My understanding is that the evidence suggests that the
LCA of life on earth was probably an extremophile who
lived around an ocean vent. An unbroken line of
vent bacteria leading from them to their modern
relatives seems like a reasonable hypothesis to
me - and I'm not currently aware of any evidence
against it.

Tim Tyler at seemysig@cyberspace.org wrote on 1/4/07 10:58 AM:

My understanding is that the evidence suggests that the
LCA of life on earth was probably an extremophile who
lived around an ocean vent. An unbroken line of
vent bacteria leading from them to their modern
relatives seems like a reasonable hypothesis to
me - and I'm not currently aware of any evidence
against it.

I agree that this would be a reasonable hypothesis to test, if only because
enough people seem to think this way. I expect that any clear evidence we
might find will bury this hypothesis. As I said in my response to Tom,
extinction and recolonization happens, and I would be very surprised if it
hadn't happened in vent communities many times over during the past 3+
billion years.

Guy A Hoelzer wrote:
Tim Tyler at seemysig@cyberspace.org wrote on 1/4/07 10:58 AM:

My understanding is that the evidence suggests that the
LCA of life on earth was probably an extremophile who
lived around an ocean vent. An unbroken line of
vent bacteria leading from them to their modern
relatives seems like a reasonable hypothesis to
me - and I'm not currently aware of any evidence
against it.

I agree that this would be a reasonable hypothesis to test, if only because
enough people seem to think this way. I expect that any clear evidence we
might find will bury this hypothesis. As I said in my response to Tom,
extinction and recolonization happens, and I would be very surprised if it
hadn't happened in vent communities many times over during the past 3+
billion years.

I am less convinced that the hypothesis will be buried.

The main data points that I am working from are the idea
that modern sulphur-eating vent bacteria are closest
to the root of the family tree of life - e.g.:

``Results of rRNA and other molecular techniques have placed
hyperthermophilic bacteria and archaea at the roots of the
phylogenetic tree of life''

...and the idea that they are similar to their distant ancestors:

``Extremophiles, especially hyperthermophiles, possess slow
“evolutionary clocks”

That is, they have not evolved much from their ancestors as compared
to other organisms

Hence, hyperthermophiles today are similar to hyperthermophiles
of over 3 billion years ago.''

[quotes from 'EXTREMOPHILES: NATURE’S ULTIMATE SURVIVORS']

That is more or less what you would expect if these
specialised organisms had more-or-less stayed put in their
own extremely stable ecosystems - but not what would be
predicted by an invasion and recolonization hypothesis
involving organisms from radically different ecosystems.

Guy A Hoelzer wrote:
Tim Tyler at seemysig@cyberspace.org wrote on 1/4/07 10:58 AM:

My understanding is that the evidence suggests that the
LCA of life on earth was probably an extremophile who
lived around an ocean vent. An unbroken line of
vent bacteria leading from them to their modern
relatives seems like a reasonable hypothesis to
me - and I'm not currently aware of any evidence
against it.

I agree that this would be a reasonable hypothesis to test, if only because
enough people seem to think this way. I expect that any clear evidence we
might find will bury this hypothesis. As I said in my response to Tom,
extinction and recolonization happens, and I would be very surprised if it
hadn't happened in vent communities many times over during the past 3+
billion years.

I am less convinced that the hypothesis will be buried.

The main data points that I am working from are the idea
that modern sulphur-eating vent bacteria are closest
to the root of the family tree of life - e.g.:

``Results of rRNA and other molecular techniques have placed
hyperthermophilic bacteria and archaea at the roots of the
phylogenetic tree of life''

....and the idea that they are similar to their distant ancestors:


``Extremophiles, especially hyperthermophiles, possess slow
„evolutionary clocks‰

That is, they have not evolved much from their ancestors as compared
to other organisms

Hence, hyperthermophiles today are similar to hyperthermophiles
of over 3 billion years ago.''

[quotes from 'EXTREMOPHILES: NATURE‚S ULTIMATE SURVIVORS']

That is more or less what you would expect if these
specialised organisms had more-or-less stayed put in their
own extremely stable ecosystems - but not what would be
predicted by an invasion and recolonization hypothesis
involving organisms from radically different ecosystems.

On Fri, 5 Jan 2007 12:19:03 -0500 (EST),
Tim Tyler <seemysig@cyberspace.org> wrote:

The main data points that I am working from are the idea
that modern sulphur-eating vent bacteria are closest
to the root of the family tree of life - e.g.:

``Results of rRNA and other molecular techniques have placed
hyperthermophilic bacteria and archaea at the roots of the
phylogenetic tree of life''

...and the idea that they are similar to their distant ancestors:

``Extremophiles, especially hyperthermophiles, possess slow
“evolutionary clocks”

That is, they have not evolved much from their ancestors as compared
to other organisms

Hence, hyperthermophiles today are similar to hyperthermophiles
of over 3 billion years ago.''

[quotes from 'EXTREMOPHILES: NATURE’S ULTIMATE SURVIVORS']

That is more or less what you would expect if these
specialised organisms had more-or-less stayed put in their
own extremely stable ecosystems - but not what would be
predicted by an invasion and recolonization hypothesis
involving organisms from radically different ecosystems.

Current ideas do not support the deep position of extremeophiles or
thermophilic archaebacteria. I've been blogging about his over the past
few weeks.

Here's the latest ...

http://sandwalk.blogspot.com/2006/12/three-domain-hypothesis-part-6.html

Even Woese agrees that the earliest forms of life constituted a community
of bacteria-like organisms that freely exchanged genes. This community
subsequently gave rise to eukaryotes on the one hand and bacteria on the
other. That's not consistent with organisms that inhabited an extreme
environment.

Larry Moran wrote:

Current ideas do not support the deep position of extremeophiles or
thermophilic archaebacteria. I've been blogging about his over the past
few weeks.

Here's the latest ...

http://sandwalk.blogspot.com/2006/12/three-domain-hypothesis-part-6.html

Even Woese agrees that the earliest forms of life constituted a community
of bacteria-like organisms that freely exchanged genes. This community
subsequently gave rise to eukaryotes on the one hand and bacteria on the
other. That's not consistent with organisms that inhabited an extreme
environment.

Your opinion in this area appears to be controversial.

For example consider this paper from Oct 29, 2006:

``Hyperthermophiles in the history of life. Stetter KO.

[...] Based on their growth requirements, HT could have existed
already on the early Earth about 3.9Gyr ago. In agreement, within the
phylogenetic tree of life, they occupy all the short deep branches
closest to the root.''