Not too long ago, I uploaded to
https://inyo7.coffeecup.com/precambrian/precambrian.html a new page,
entitled "Field Trip To The Alexander Hills Fossil District,
California." Includes a detailed text, with fully captioned on-site
images and photographs of fossils.

It's a fascinating paleontological place, indeed, situated outside the
southern sector of Death Valley National Park. The Precambrian sequence,
for example, not only yields stromatolites, concentrically laminated
cyanobacterial structures roughly 1.2 billion years old, but also some
of Earth's earliest shell-bearing organisms, skeletal elements from
eukaryotic unicellular testate amoebae over three-quarters of a billion
years old. Miocene strata produce exceptionally well preserved petrified
palm and dicotyledon wood, permineralized grasses, and camel tracks. And
the Pliocene-Pleistocene section contains loads of vertebrate remains,
including mammoths, a mastodon, camels, large and small horses, a llama,
a large antelope, microtine rodents (the voles, lemmings, and muskrats),
and a flamingo--plus, such invertebrate kinds as freshwater gastropods,
ostracods (a diminutive bivalved crustacean), and diatoms (single-celled
photosynthesizing algae).

On 4/18/2023 3:17 PM, Inyo wrote:
> Not too long ago, I uploaded to
> https://inyo7.coffeecup.com/precambrian/precambrian.html a new page,
> entitled "Field Trip To The Alexander Hills Fossil District,
> California." Includes a detailed text, with fully captioned on-site
> images and photographs of fossils.
>
> It's a fascinating paleontological place, indeed, situated outside the
> southern sector of Death Valley National Park. The Precambrian sequence,
> for example, not only yields stromatolites, concentrically laminated
> cyanobacterial structures roughly 1.2 billion years old, but also some
> of Earth's earliest shell-bearing organisms, skeletal elements from
> eukaryotic unicellular testate amoebae over three-quarters of a billion
> years old. Miocene strata produce exceptionally well preserved petrified
> palm and dicotyledon wood, permineralized grasses, and camel tracks. And
> the Pliocene-Pleistocene section contains loads of vertebrate remains,
> including mammoths, a mastodon, camels, large and small horses, a llama,
> a large antelope, microtine rodents (the voles, lemmings, and muskrats),
> and a flamingo--plus, such invertebrate kinds as freshwater gastropods,
> ostracods (a diminutive bivalved crustacean), and diatoms (single-celled
> photosynthesizing algae).

I neglected to mention that the early Cambrian sequence provides not
only the first trilobites in the regional stratigraphic succession, but
also archaeocyathids (extinct calcareous sponge), annelid and arthropod
tracks and trails (ichnofossils), and perhaps the earliest evidence of
echinoderms in the fossil record.

On Tuesday, April 18, 2023 at 4:28:48 PM UTC-7, Inyo wrote:
> On 4/18/2023 3:17 PM, Inyo wrote:
> > Not too long ago, I uploaded to
> > https://inyo7.coffeecup.com/precambrian/precambrian.html a new page,
> > entitled "Field Trip To The Alexander Hills Fossil District,
> > California." Includes a detailed text, with fully captioned on-site
> > images and photographs of fossils.
> >
> > It's a fascinating paleontological place, indeed, situated outside the
> > southern sector of Death Valley National Park. The Precambrian sequence,
> > for example, not only yields stromatolites, concentrically laminated
> > cyanobacterial structures roughly 1.2 billion years old, but also some
> > of Earth's earliest shell-bearing organisms, skeletal elements from
> > eukaryotic unicellular testate amoebae over three-quarters of a billion
> > years old. Miocene strata produce exceptionally well preserved petrified
> > palm and dicotyledon wood, permineralized grasses, and camel tracks. And
> > the Pliocene-Pleistocene section contains loads of vertebrate remains,
> > including mammoths, a mastodon, camels, large and small horses, a llama,
> > a large antelope, microtine rodents (the voles, lemmings, and muskrats),
> > and a flamingo--plus, such invertebrate kinds as freshwater gastropods,
> > ostracods (a diminutive bivalved crustacean), and diatoms (single-celled
> > photosynthesizing algae).
> I neglected to mention that the early Cambrian sequence provides not
> only the first trilobites in the regional stratigraphic succession, but
> also archaeocyathids (extinct calcareous sponge), annelid and arthropod
> tracks and trails (ichnofossils), and perhaps the earliest evidence of
> echinoderms in the fossil record.

Thanks for this guide! The earliest echinoderms (such as helicoplacoids) were very
loosely bonded creatures. The location in the White Mountains containing one of the
denser deposits of them present many shale facies with many disaggregated platelets,
but no full specimens. If there were even earlier echinoderm organisms, they may have
been at least as loosely contructed. The Poleta formation at the same location presents
many complete trilobite specimens. Interestingly many of them exhibit plastic deformation
that must have occurred some time after fossiization.

I've been too wrapped up in talk.origins lately, and I only saw this yesterday for the first time.
I hope you are still around to see my appreciative comments below, Inyo.

On Tuesday, April 18, 2023 at 6:17:05 PM UTC-4, Inyo wrote:
> Not too long ago, I uploaded to
> https://inyo7.coffeecup.com/precambrian/precambrian.html a new page,
> entitled "Field Trip To The Alexander Hills Fossil District,
> California." Includes a detailed text, with fully captioned on-site
> images and photographs of fossils.

Excellent, and a much needed relief from the "noisy" threads that have,
alas, been all too prevalent here.

It is such a superb page that I sent a link to a close relative who
is keenly interested in fossils, especially precambrian ones, including
stromatolites. He lives in Australia, and Shark Bay has perhaps the most
well known living example of such formations.

> It's a fascinating paleontological place, indeed, situated outside the
> southern sector of Death Valley National Park. The Precambrian sequence,
> for example, not only yields stromatolites, concentrically laminated
> cyanobacterial structures roughly 1.2 billion years old, but also some
> of Earth's earliest shell-bearing organisms, skeletal elements from
> eukaryotic unicellular testate amoebae over three-quarters of a billion years old.

Your detailed comments on them were especially interesting to me:

> Next up is the overlying Beck Spring Dolomite, around 787 to 732 million years old. The dominantly magnesium carbonate sequence contains stromatolites and numerous kinds of eukaryotic cells, including vase-shaped microfossils produced by a testate shell-secreting amoeba; a chert layer near the base of the Beck Spring Dolomite yielded one of the oldest shells in the fossil record, a skeletal element from one of those testate amoeba dated at roughly 780 million years old--called scientifically, Cycliocyrillium. For geochronological perspective, the oldest known evidence of a shell-bearing organism comes from the 809 million year old Fifteenmile Group in Yukon, Canada..

These dates are very interesting, in light of the following information:

"The oldest known eukaryote fossils, multicellular planktonic organisms belonging to the Gabonionta, were discovered in Gabon in 2023, dating back to 2.1 billion years ago.[5]
....
Whenever their origins, eukaryotes may not have become ecologically dominant until much later; a massive increase in the zinc composition of marine sediments 800 million years ago has been attributed to the rise of substantial populations of eukaryotes, which preferentially consume and incorporate zinc relative to prokaryotes, approximately a billion years after their origin (at the latest).[81]

https://en.wikipedia.org/wiki/Eukaryote

This suggests that there might have been an "arms race" that caused some eukaryotes to produce shells.
A similar "arms race" is believed to be responsible for similar features of the Cambrian explosion.
And it is widely opined that the buildup of oxygen in the atmosphere was the main stimulus.
It is fascinating to think that a buildup of zinc was that kind stimulus about 300 million years earlier.

[5] is: El Albani, Abderrazak. "A search for life in Palaeoproterozoic marine sediments using Zn isotopes and geochemistry". Earth and Planetary Science Letters. 623. doi:10.1016/j.epsl.2023.118169.

I hope you keep returning to sci.bio.paleontology, Inyo. Your posts are not only
a delight to the eyes and mind, but in this one you've been very thought-provoking.

Peter Nyikos
Professor, Dept. of Mathematics -- standard disclaimer--
University of South Carolina
http://people.math.sc.edu/nyikos

On 5/8/23 9:58 AM, Peter Nyikos wrote:
> I've been too wrapped up in talk.origins lately, and I only saw this yesterday for the first time.
> I hope you are still around to see my appreciative comments below, Inyo.
>
> On Tuesday, April 18, 2023 at 6:17:05 PM UTC-4, Inyo wrote:
>> Not too long ago, I uploaded to
>> https://inyo7.coffeecup.com/precambrian/precambrian.html a new page,
>> entitled "Field Trip To The Alexander Hills Fossil District,
>> California." Includes a detailed text, with fully captioned on-site
>> images and photographs of fossils.
>
> Excellent, and a much needed relief from the "noisy" threads that have,
> alas, been all too prevalent here.
>
> It is such a superb page that I sent a link to a close relative who
> is keenly interested in fossils, especially precambrian ones, including
> stromatolites. He lives in Australia, and Shark Bay has perhaps the most
> well known living example of such formations.
>
>
>> It's a fascinating paleontological place, indeed, situated outside the
>> southern sector of Death Valley National Park. The Precambrian sequence,
>> for example, not only yields stromatolites, concentrically laminated
>> cyanobacterial structures roughly 1.2 billion years old, but also some
>> of Earth's earliest shell-bearing organisms, skeletal elements from
>> eukaryotic unicellular testate amoebae over three-quarters of a billion years old.
>
> Your detailed comments on them were especially interesting to me:
>
>> Next up is the overlying Beck Spring Dolomite, around 787 to 732 million years old. The dominantly magnesium carbonate sequence contains stromatolites and numerous kinds of eukaryotic cells, including vase-shaped microfossils produced by a testate shell-secreting amoeba; a chert layer near the base of the Beck Spring Dolomite yielded one of the oldest shells in the fossil record, a skeletal element from one of those testate amoeba dated at roughly 780 million years old--called scientifically, Cycliocyrillium. For geochronological perspective, the oldest known evidence of a shell-bearing organism comes from the 809 million year old Fifteenmile Group in Yukon, Canada.
>
> These dates are very interesting, in light of the following information:
>
> "The oldest known eukaryote fossils, multicellular planktonic organisms belonging to the Gabonionta, were discovered in Gabon in 2023, dating back to 2.1 billion years ago.[5]
> ...
> Whenever their origins, eukaryotes may not have become ecologically dominant until much later; a massive increase in the zinc composition of marine sediments 800 million years ago has been attributed to the rise of substantial populations of eukaryotes, which preferentially consume and incorporate zinc relative to prokaryotes, approximately a billion years after their origin (at the latest).[81]
>
> https://en.wikipedia.org/wiki/Eukaryote
>
> This suggests that there might have been an "arms race" that caused some eukaryotes to produce shells.
> A similar "arms race" is believed to be responsible for similar features of the Cambrian explosion.
> And it is widely opined that the buildup of oxygen in the atmosphere was the main stimulus.
> It is fascinating to think that a buildup of zinc was that kind stimulus about 300 million years earlier.
>
> [5] is: El Albani, Abderrazak. "A search for life in Palaeoproterozoic marine sediments using Zn isotopes and geochemistry". Earth and Planetary Science Letters. 623. doi:10.1016/j.epsl.2023.118169.

Interesting thought, but it seems as if that paper says the opposite,
that the increase in zinc up column is an indication and result of
increased eukaryote abundance and size, not a cause.

"Given the multiple biological requirements for Zn, its concomitant
increase in concentration and LF size up strata may simply reflect the
greater Zn demand with increasing cell volume."

> I hope you keep returning to sci.bio.paleontology, Inyo. Your posts are not only
> a delight to the eyes and mind, but in this one you've been very thought-provoking.
>
>
> Peter Nyikos
> Professor, Dept. of Mathematics -- standard disclaimer--
> University of South Carolina
> http://people.math.sc.edu/nyikos
>
>

On Monday, May 8, 2023 at 1:30:54 PM UTC-4, John Harshman wrote:
> On 5/8/23 9:58 AM, Peter Nyikos wrote:
> > I've been too wrapped up in talk.origins lately, and I only saw this yesterday for the first time.
> > I hope you are still around to see my appreciative comments below, Inyo..
> >
> > On Tuesday, April 18, 2023 at 6:17:05 PM UTC-4, Inyo wrote:
> >> Not too long ago, I uploaded to
> >> https://inyo7.coffeecup.com/precambrian/precambrian.html a new page,
> >> entitled "Field Trip To The Alexander Hills Fossil District,
> >> California." Includes a detailed text, with fully captioned on-site
> >> images and photographs of fossils.
> >
> > Excellent, and a much needed relief from the "noisy" threads that have,
> > alas, been all too prevalent here.
> >
> > It is such a superb page that I sent a link to a close relative who
> > is keenly interested in fossils, especially precambrian ones, including
> > stromatolites. He lives in Australia, and Shark Bay has perhaps the most
> > well known living example of such formations.
> >
> >
> >> It's a fascinating paleontological place, indeed, situated outside the
> >> southern sector of Death Valley National Park. The Precambrian sequence,
> >> for example, not only yields stromatolites, concentrically laminated
> >> cyanobacterial structures roughly 1.2 billion years old, but also some
> >> of Earth's earliest shell-bearing organisms, skeletal elements from
> >> eukaryotic unicellular testate amoebae over three-quarters of a billion years old.
> >
> > Your detailed comments on them were especially interesting to me:
> >
> >> Next up is the overlying Beck Spring Dolomite, around 787 to 732 million years old. The dominantly magnesium carbonate sequence contains stromatolites and numerous kinds of eukaryotic cells, including vase-shaped microfossils produced by a testate shell-secreting amoeba; a chert layer near the base of the Beck Spring Dolomite yielded one of the oldest shells in the fossil record, a skeletal element from one of those testate amoeba dated at roughly 780 million years old--called scientifically, Cycliocyrillium. For geochronological perspective, the oldest known evidence of a shell-bearing organism comes from the 809 million year old Fifteenmile Group in Yukon, Canada.
> >
> > These dates are very interesting, in light of the following information:
> >
> > "The oldest known eukaryote fossils, multicellular planktonic organisms belonging to the Gabonionta, were discovered in Gabon in 2023, dating back to 2.1 billion years ago.[5]
> > ...
> > Whenever their origins, eukaryotes may not have become ecologically dominant until much later; a massive increase in the zinc composition of marine sediments 800 million years ago has been attributed to the rise of substantial populations of eukaryotes, which preferentially consume and incorporate zinc relative to prokaryotes, approximately a billion years after their origin (at the latest).[81]
> >
> > https://en.wikipedia.org/wiki/Eukaryote
> >
> > This suggests that there might have been an "arms race" that caused some eukaryotes to produce shells.
> > A similar "arms race" is believed to be responsible for similar features of the Cambrian explosion.
> > And it is widely opined that the buildup of oxygen in the atmosphere was the main stimulus.
> > It is fascinating to think that a buildup of zinc was that kind stimulus about 300 million years earlier.
> >
> > [5] is: El Albani, Abderrazak. "A search for life in Palaeoproterozoic marine sediments using Zn isotopes and geochemistry". Earth and Planetary Science Letters. 623. doi:10.1016/j.epsl.2023.118169.

> Interesting thought, but it seems as if that paper says the opposite,
> that the increase in zinc up column is an indication and result of
> increased eukaryote abundance and size, not a cause.

It is much more nuanced: note the word "may":

> "Given the multiple biological requirements for Zn, its concomitant
> increase in concentration and LF size up strata may simply reflect the
> greater Zn demand with increasing cell volume."

You may :-)
be guilty of a false dichotomy. There may have been a big increase
in the available zinc due to geological events, in a form
eukaryotes could utilize. It is undeniable that they DID use it,
and what we are finding is the result of much recycling of the zinc.

The increase in oxygen in the atmosphere predated the Cambrian explosion,
but it is commonly said in talk.origins that the explosion was precipitated
when it reached a critical level.

I can still recall an article from my youth, probably by Isaac Asimov, where phosphorus
was called the great bottleneck for life, limiting the amount of living biomass
that can exist on earth at any one time, more so than other elements.
This bottleneck may date back to well before the first eukaryotes
and possibly the first prokaryotes.

Peter Nyikos
Professor, Dept. of Mathematics -- standard disclaimer--
Univ. of South Carolina at Columbia
http://people.math.sc.edu/nyikos

> > I hope you keep returning to sci.bio.paleontology, Inyo. Your posts are not only
> > a delight to the eyes and mind, but in this one you've been very thought-provoking.

On Monday, May 8, 2023 at 2:55:26 PM UTC-7, Peter Nyikos wrote:
> On Monday, May 8, 2023 at 1:30:54 PM UTC-4, John Harshman wrote:
> > On 5/8/23 9:58 AM, Peter Nyikos wrote:
> > > I've been too wrapped up in talk.origins lately, and I only saw this yesterday for the first time.
> > > I hope you are still around to see my appreciative comments below, Inyo.
> > >
> > > On Tuesday, April 18, 2023 at 6:17:05 PM UTC-4, Inyo wrote:
> > >> Not too long ago, I uploaded to
> > >> https://inyo7.coffeecup.com/precambrian/precambrian.html a new page,
> > >> entitled "Field Trip To The Alexander Hills Fossil District,
> > >> California." Includes a detailed text, with fully captioned on-site
> > >> images and photographs of fossils.
> > >
> > > Excellent, and a much needed relief from the "noisy" threads that have,
> > > alas, been all too prevalent here.
> > >
> > > It is such a superb page that I sent a link to a close relative who
> > > is keenly interested in fossils, especially precambrian ones, including
> > > stromatolites. He lives in Australia, and Shark Bay has perhaps the most
> > > well known living example of such formations.
> > >
> > >
> > >> It's a fascinating paleontological place, indeed, situated outside the
> > >> southern sector of Death Valley National Park. The Precambrian sequence,
> > >> for example, not only yields stromatolites, concentrically laminated
> > >> cyanobacterial structures roughly 1.2 billion years old, but also some
> > >> of Earth's earliest shell-bearing organisms, skeletal elements from
> > >> eukaryotic unicellular testate amoebae over three-quarters of a billion years old.
> > >
> > > Your detailed comments on them were especially interesting to me:
> > >
> > >> Next up is the overlying Beck Spring Dolomite, around 787 to 732 million years old. The dominantly magnesium carbonate sequence contains stromatolites and numerous kinds of eukaryotic cells, including vase-shaped microfossils produced by a testate shell-secreting amoeba; a chert layer near the base of the Beck Spring Dolomite yielded one of the oldest shells in the fossil record, a skeletal element from one of those testate amoeba dated at roughly 780 million years old--called scientifically, Cycliocyrillium. For geochronological perspective, the oldest known evidence of a shell-bearing organism comes from the 809 million year old Fifteenmile Group in Yukon, Canada.
> > >
> > > These dates are very interesting, in light of the following information:
> > >
> > > "The oldest known eukaryote fossils, multicellular planktonic organisms belonging to the Gabonionta, were discovered in Gabon in 2023, dating back to 2.1 billion years ago.[5]
> > > ...
> > > Whenever their origins, eukaryotes may not have become ecologically dominant until much later; a massive increase in the zinc composition of marine sediments 800 million years ago has been attributed to the rise of substantial populations of eukaryotes, which preferentially consume and incorporate zinc relative to prokaryotes, approximately a billion years after their origin (at the latest).[81]
> > >
> > > https://en.wikipedia.org/wiki/Eukaryote
> > >
> > > This suggests that there might have been an "arms race" that caused some eukaryotes to produce shells.
> > > A similar "arms race" is believed to be responsible for similar features of the Cambrian explosion.
> > > And it is widely opined that the buildup of oxygen in the atmosphere was the main stimulus.
> > > It is fascinating to think that a buildup of zinc was that kind stimulus about 300 million years earlier.
> > >
> > > [5] is: El Albani, Abderrazak. "A search for life in Palaeoproterozoic marine sediments using Zn isotopes and geochemistry". Earth and Planetary Science Letters. 623. doi:10.1016/j.epsl.2023.118169.
>
> > Interesting thought, but it seems as if that paper says the opposite,
> > that the increase in zinc up column is an indication and result of
> > increased eukaryote abundance and size, not a cause.
> It is much more nuanced: note the word "may":
> > "Given the multiple biological requirements for Zn, its concomitant
> > increase in concentration and LF size up strata may simply reflect the
> > greater Zn demand with increasing cell volume."
> You may :-)
> be guilty of a false dichotomy. There may have been a big increase
> in the available zinc due to geological events, in a form
> eukaryotes could utilize. It is undeniable that they DID use it,
> and what we are finding is the result of much recycling of the zinc.
>
> The increase in oxygen in the atmosphere predated the Cambrian explosion,
> but it is commonly said in talk.origins that the explosion was precipitated
> when it reached a critical level.
>
>
> I can still recall an article from my youth, probably by Isaac Asimov, where phosphorus
> was called the great bottleneck for life, limiting the amount of living biomass
> that can exist on earth at any one time, more so than other elements.
> This bottleneck may date back to well before the first eukaryotes
> and possibly the first prokaryotes.
> Peter Nyikos
> Professor, Dept. of Mathematics -- standard disclaimer--
> Univ. of South Carolina at Columbia
> http://people.math.sc.edu/nyikos
> > > I hope you keep returning to sci.bio.paleontology, Inyo. Your posts are not only
> > > a delight to the eyes and mind, but in this one you've been very thought-provoking.

I happened to glance at this, and I'm a little amazed. You are really out of touch with
paleontological progress since your youth. There was a Great Oxygenization Event
(~ 2.4 - 2.0 Gya) and the Francevillian biota (~2.1 Gya) that you might acquaint yourself
with.

On Monday, May 8, 2023 at 6:50:32 PM UTC-4, erik simpson wrote:
> On Monday, May 8, 2023 at 2:55:26 PM UTC-7, Peter Nyikos wrote:
> > On Monday, May 8, 2023 at 1:30:54 PM UTC-4, John Harshman wrote:
> > > On 5/8/23 9:58 AM, Peter Nyikos wrote:
> > > > I've been too wrapped up in talk.origins lately, and I only saw this yesterday for the first time.
> > > > I hope you are still around to see my appreciative comments below, Inyo.
> > > >
> > > > On Tuesday, April 18, 2023 at 6:17:05 PM UTC-4, Inyo wrote:
> > > >> Not too long ago, I uploaded to
> > > >> https://inyo7.coffeecup.com/precambrian/precambrian.html a new page,
> > > >> entitled "Field Trip To The Alexander Hills Fossil District,
> > > >> California." Includes a detailed text, with fully captioned on-site
> > > >> images and photographs of fossils.
> > > >
> > > > Excellent, and a much needed relief from the "noisy" threads that have,
> > > > alas, been all too prevalent here.
> > > >
> > > > It is such a superb page that I sent a link to a close relative who
> > > > is keenly interested in fossils, especially precambrian ones, including
> > > > stromatolites. He lives in Australia, and Shark Bay has perhaps the most
> > > > well known living example of such formations.
> > > >
> > > >
> > > >> It's a fascinating paleontological place, indeed, situated outside the
> > > >> southern sector of Death Valley National Park. The Precambrian sequence,
> > > >> for example, not only yields stromatolites, concentrically laminated
> > > >> cyanobacterial structures roughly 1.2 billion years old, but also some
> > > >> of Earth's earliest shell-bearing organisms, skeletal elements from
> > > >> eukaryotic unicellular testate amoebae over three-quarters of a billion years old.
> > > >
> > > > Your detailed comments on them were especially interesting to me:
> > > >
> > > >> Next up is the overlying Beck Spring Dolomite, around 787 to 732 million years old. The dominantly magnesium carbonate sequence contains stromatolites and numerous kinds of eukaryotic cells, including vase-shaped microfossils produced by a testate shell-secreting amoeba; a chert layer near the base of the Beck Spring Dolomite yielded one of the oldest shells in the fossil record, a skeletal element from one of those testate amoeba dated at roughly 780 million years old--called scientifically, Cycliocyrillium. For geochronological perspective, the oldest known evidence of a shell-bearing organism comes from the 809 million year old Fifteenmile Group in Yukon, Canada.
> > > >
> > > > These dates are very interesting, in light of the following information:
> > > >
> > > > "The oldest known eukaryote fossils, multicellular planktonic organisms belonging to the Gabonionta, were discovered in Gabon in 2023, dating back to 2.1 billion years ago.[5]
> > > > ...
> > > > Whenever their origins, eukaryotes may not have become ecologically dominant until much later; a massive increase in the zinc composition of marine sediments 800 million years ago has been attributed to the rise of substantial populations of eukaryotes, which preferentially consume and incorporate zinc relative to prokaryotes, approximately a billion years after their origin (at the latest).[81]
> > > >
> > > > https://en.wikipedia.org/wiki/Eukaryote
> > > >
> > > > This suggests that there might have been an "arms race" that caused some eukaryotes to produce shells.
> > > > A similar "arms race" is believed to be responsible for similar features of the Cambrian explosion.
> > > > And it is widely opined that the buildup of oxygen in the atmosphere was the main stimulus.
> > > > It is fascinating to think that a buildup of zinc was that kind stimulus about 300 million years earlier.
> > > >
> > > > [5] is: El Albani, Abderrazak. "A search for life in Palaeoproterozoic marine sediments using Zn isotopes and geochemistry". Earth and Planetary Science Letters. 623. doi:10.1016/j.epsl.2023.118169.
> >
> > > Interesting thought, but it seems as if that paper says the opposite,
> > > that the increase in zinc up column is an indication and result of
> > > increased eukaryote abundance and size, not a cause.
> > It is much more nuanced: note the word "may":
> > > "Given the multiple biological requirements for Zn, its concomitant
> > > increase in concentration and LF size up strata may simply reflect the
> > > greater Zn demand with increasing cell volume."
> > You may :-)
> > be guilty of a false dichotomy. There may have been a big increase
> > in the available zinc due to geological events, in a form
> > eukaryotes could utilize. It is undeniable that they DID use it,
> > and what we are finding is the result of much recycling of the zinc.
> >
> > The increase in oxygen in the atmosphere predated the Cambrian explosion,
> > but it is commonly said in talk.origins that the explosion was precipitated
> > when it reached a critical level.
> >
> >
> > I can still recall an article from my youth, probably by Isaac Asimov, where phosphorus
> > was called the great bottleneck for life, limiting the amount of living biomass
> > that can exist on earth at any one time, more so than other elements.
> > This bottleneck may date back to well before the first eukaryotes
> > and possibly the first prokaryotes.
> > Peter Nyikos
> > Professor, Dept. of Mathematics -- standard disclaimer--
> > Univ. of South Carolina at Columbia
> > http://people.math.sc.edu/nyikos
> > > > I hope you keep returning to sci.bio.paleontology, Inyo. Your posts are not only
> > > > a delight to the eyes and mind, but in this one you've been very thought-provoking.

> I happened to glance at this, and I'm a little amazed.

At what? your own temerity in trolling as follows?
> You are really out of touch with
> paleontological progress since your youth.

Your insult is without any basis in reality. But I'm pretty sure you know that,
because you completely acquiesced in what I wrote about phosphorus.

> There was a Great Oxygenization Event
> (~ 2.4 - 2.0 Gya) and the Francevillian biota (~2.1 Gya) that you might acquaint yourself
> with.

I've known about the first one for years, and more recently about the second,
but they are not directly relevant to anything I wrote.

They are, of course, relevant to the first appearance of numerous eukaryotes
[see my reference back four posts ago, above],
which need oxygen at a high level, but NOT to the extent that metazoans do,
especially those with billions of individual cells. They had to wait for
about a billion and a half additional years, to near the time of the Cambrian explosion [see above again].

And don't get me wrong, your comments would have been welcome if
sincere discussion had been your aim, but your failure to back your insult
with a rebuttal to the phosphorus bottleneck shows the lack of any such aim.

Peter Nyikos
Professor, Dept. of Mathematics -- standard disclaimer--
Univ. of South Carolina at Columbia
http://people.math.sc.edu/nyikos

PS Over in talk origins, you wrote the following to me:

"Tell you what: I don't use killfiles, since I'm a troglodyte using GG, but I'll make a good imitation by
promising I won't even look at what you post for some undefined time. When in the future I check back,
if I see the same rubbish being posted, I'll continue on that line."

https://groups.google.com/g/talk.origins/c/os5qbdFmXvs/m/Ce2JYU1HAwAJ
Mar 31, 2023, 11:40:07 AM

Will you play "blame the victim" by calling my reaction to your trolling "rubbish"
as justification for a new use of your "de facto killfile"?