Pondering the Precambrian #4

NeoProterozoic:

Ediacaran:

From Brazil, Ediacaran vase shaped fossils have been found.  is this the earliest known protist fossils yet?

How are the various frond critters of the Ediacaran related to each other?

How did the Ediacaran critter Dickinsonia grow?

A mixed Cloudinia-Corumbella-Namacalathus assemblage shows increasing ecological complexity over the course of the Ediacaran.

Cryogenian:

Did a freshwater layer exist on the world's oceans and persist after the Snowball Earth episodes like the one in the Cryogenian?

As the Snowball Earth ended, how much oxygen weathering took place and what were the biotic impacts?

Tonian:

There was a huge Andes-like mountain range on the northwest of Rodinia that may have lasted for 100 million years during the Tonian 800 million years ago.

MesoProterozoic:

Wind patterns have been inferred from dunes from Calymmian Brazil.

The diversity of Eukaryote microfossils of Calymmian China is impressive.

PaleoProterozoic:

In Statherian China, there is evidence of a sillicified microbiota from the Dahongyu Formation.

The Sudbury Impact appears to have caused long lived volcanic eruptions during the Orosirian PaleoProterozoic.  Since it was one of 150 impacts within a relatively short period, combined with this above volcanism, it should be no surprise life didn't recover to take a second stab at complexity for a billion years.

The Sudbury Basin continued to have geothermal heat during the Huronian snowball earth.

Can the Rhyacian/Siderian Glaciations (huronian snowball earth) be dated based on subglacial hydrothermal activity?

Beginning in the Siderian, ancient carbon was subsumed into the Earth's mantle.

Did anaerobic oxygenic photosynthesis (read the paper) come about in cyanobacteria prior to modern aerobic photosynthesis?

During the Siderian, Earth had a hazy, methane filled atmosphere.

Did eukaryotes arise during the Siderian?

Archean:

Lenticular organisms from South Africa are related to the Pilbara forms.

Did life arise during the EoArchean WITHOUT using phosphate?

Fossils were found from the Eoarchean 3.77 billion years ago in Quebec, Canada.

How did the crust form?

Hadean:

The Earth probably began with a solid shell for a crust, like Mars.

META:

New branches have been found in Archaea.

Iron eating, methanogen organisms probably kept the Earth warm for its first 2 billion years.

Mineral self assembly was common in the early years of the Earth.

Extraordinary Claim: Venus COuld be the Source of Complex Life on Earth

The Venus Hypothesis

Author:

Cartwright

Abstract:

Current models indicate that Venus may have been habitable. Complex life may have evolved on the highly irradiated Venus, and transferred to Earth on asteroids. This model fits the pattern of pulses of highly developed life appearing, diversifying and going extinct with astonishing rapidity through the Cambrian and Ordovician periods, and also explains the extraordinary genetic variety which appeared over this period.

Macroscopic (complex?) Eukaryotes From the Calymmian MesoProterozoic One Billion Years Before the Cambrian Explosion

Decimetre-scale multicellular eukaryotes from the 1.56-billion-year-old Gaoyuzhuang Formation in North China

Authors:

Zhu et al

Abstract:

Fossils of macroscopic eukaryotes are rarely older than the Ediacaran Period (635–541 million years (Myr)), and their interpretation remains controversial. Here, we report the discovery of macroscopic fossils from the 1,560-Myr-old Gaoyuzhuang Formation, Yanshan area, North China, that exhibit both large size and regular morphology. Preserved as carbonaceous compressions, the Gaoyuzhuang fossils have statistically regular linear to lanceolate shapes up to 30 cm long and nearly 8 cm wide, suggesting that the Gaoyuzhuang fossils record benthic multicellular eukaryotes of unprecedentedly large size. Syngenetic fragments showing closely packed ~10 μm cells arranged in a thick sheet further reinforce the interpretation. Comparisons with living thalloid organisms suggest that these organisms were photosynthetic, although their phylogenetic placement within the Eukarya remains uncertain. The new fossils provide the strongest evidence yet that multicellular eukaryotes with decimetric dimensions and a regular developmental program populated the marine biosphere at least a billion years before the Cambrian Explosion.

Studing Gonium pectorale to Explaint he Origin of Complex Life

Throughout the history of life on Earth, multicellular life evolved from single cells numerous times, but explaining how this happened is one of the major evolutionary puzzles of our time. However, scientists have now completed a study of the complete DNA of one of the most important model organisms, Gonium pectorale, a simple green algae that comprises only 16 cells.

This microscopic organism is helping to fill the evolutionary gap in our understanding. The two year research project was a global collaboration between Kansas State University, Universities of Arizona and Tokyo, and Wits University. It is documented in the prestigious journal Nature Communications.

Pierre Durand, a researcher in the department of Molecular Medicine and Haematology and the Evolutionary Studies Institute at Wits University is one of the project collaborators.

"The evolution from unicellular to multicellular life was a big deal. It changed the way the planet would be forever. From worms to insects, the dinosaurs, grasses, flowering plants, hadedas and humans, you just have to look around and see the extraordinary forms of multicellular existence," says Durand.

"It has been difficult to explain how this occurred because it was not an easy thing to have happened. So questions like 'why did single cells live together in groups at the very beginning of multicellularity when it puts them at a fitness disadvantage?' challenged us for a long time," says Durand. We still don't know most of the answers but this project has certainly filled one of the gaps in our current understanding.

There are many model systems for studying multicellularity but nothing quite like the volvocine green algae, the group to which G. pectorale belongs.

"The evolutionary transition to multicellularity has occurred numerous times in all domains of life, yet the evolutionary history of this transition is not well understood. However, the volvocine green algae include a diverse variety of unicellular, colonial, and multicellular species," says Durand.

link.

Without ancestral gene life on Earth might not have evolved beyond slime

Researchers at the University of British Columbia have identified a common ancestral gene that enabled the evolution of advanced life over a billion years ago.

The gene, found in all complex organisms, including plants and animals, encodes for a large group of enzymes known as protein kinases that enabled cells to be larger and to rapidly transfer information from one part to another.

"If the duplications and subsequent mutations of this gene during evolution didn't happen, then life would be completely different today," said Steven Pelech, a professor in Division of Neurology in the UBC Faculty of Medicine. "The most advanced life on our planet would probably still be bacterial slime."

Plants, animals, mushrooms and more all exist because they are made up of eukaryotic cells that are larger and far more complex than bacteria. Inside of these eukaryotic cells are hundreds of organelles that perform diverse functions to keep them living, just as different organs do for the human body.

The new research, published this week in the Journal of Biological Chemistry, identifies the gene that gave rise to protein kinases. On a cellular scale, these highly interactive signaling proteins play a role similar to the neurons in the brain by transferring information throughout the cell by a process known as protein phosphorylation.

This ability to transmit signals from one part of the cell to another not only enabled cells to become more complex internally, but also allowed cells to come together to form systems, paving the way for the evolution of intelligent life.

link.

The Ediacaran Period: Glimpses of the Earth's Earliest Animals (a lecture)

Oxygen Sharply Rose 100 Million Years Before Ediacaran Biota Evolved

It took 100 million years for oxygen levels in the oceans and atmosphere to increase to the level that allowed the explosion of animal life on Earth about 600 million years ago, according to a UCL-led study funded by the Natural Environment Research Council.

Before now it was not known how quickly Earth's oceans and atmosphere became oxygenated and if animal life expanded before or after oxygen levels rose. The new study, published today in Nature Communications, shows the increase began significantly earlier than previously thought and occurred in fits and starts spread over a vast period. It is therefore likely that early animal evolution was kick-started by increased amounts of oxygen, rather than a change in animal behaviour leading to oxygenation.

Lead researcher, Dr Philip Pogge von Strandmann (UCL Earth Sciences), said: "We want to find out how the evolution of life links to the evolution of our climate. The question on how strongly life has actively modified Earth's climate, and why the Earth has been habitable for so long is extremely important for understanding both the climate system, and why life is on Earth in the first place."

Researchers from UCL, Birkbeck, Bristol University, University of Washington, University of Leeds, Utah State University and University of Southern Denmark tracked what was happening with oxygen levels globally 770 - 520 million years ago (Ma) using new tracers in rocks across the US, Canada and China.

link.

Did the Oceans get Arsenic Poisoning at the end of the Huronian Glaciations/Siderian PaleoProterozoic Snowball Earth?

By examining rocks at the bottom of ancient oceans, an international group of researchers have revealed that arsenic concentrations in the oceans have varied greatly over time. But also that in the very early oceans, arsenic co-varied with the rise of atmospheric oxygen and coincided with the coming and going of global glaciations. The study was recently published in the Nature Group Journal, Scientific Reports.

"In the article we argue that when we first see the appearance of complex life on Earth, is when life have developed mechanisms to resist catastrophic chemical changes forced by global glaciations. And that this enabled the expansion of complex life in oceans, and paved the way for our own evolution", says Dr Ernest Chi Fru of Stockholm University, who has led the research group.

The first appearance of oxygen in the atmosphere occurred at a time when marine arsenic concentrations were dramatically low, at about after 2.45 billion years ago. This is also a period when Earth experienced its first known global glaciation. At the end of these glaciations, considerable rise in marine arsenic concentrations concurred with rapid demise of atmospheric oxygen.

The authors infer -- from the way modern photosynthetic organisms react to changing marine arsenic concentrations -- that this event was due to widespread ocean toxicity resulting from the release of toxic elements into the oceans when the ice melted.

link.

An Overview of the Revolutionary Nature of the NeoProterozoic

The Neoproterozoic

Author:

Butterfield

Abstract:

The Neoproterozoic era was arguably the most revolutionary in Earth history. Extending from 1000 to 541 million years ago, it stands at the intersection of the two great tracts of evolutionary time: on the one side, some three billion years of pervasively microbial ‘Precambrian’ life, and on the other the modern ‘Phanerozoic’ biosphere with its extraordinary diversity of large multicellular organisms. The disturbance doesn’t stop here, however: over this same stretch of time the planet itself was in the throes of change. Tectonically, it saw major super-continental reconfigurations, climatically its deepest ever glacial freeze, and geochemically some of the most anomalous perturbations on record. What lies behind this dramatic convergence of biological and geological phenomena, and how exactly did it give rise to the curiously complex world that we now inhabit?

The Paleo Recipe for Complex Life on Earth

Let's step back through deep time to consider an intriguing event. One which has been written about, but far from sufficiently and its existence could have some pretty profound implications about Earth and life's history.

 

Looking back to the Precambrian.  

The Earth is racked by global glaciations.  Ones which have been called the Snowball Earth.  They stretch over the entire planet from the poles through the equator.  There is some dispute whether or not the oceans were completely frozen over (a slushball earth vs snowball), but the glaciations are acknowledged as real.

The monstrous glaciation is understood to have been triggered by a sudden drop in the atmospheric carbon dioxide levels.  This, in turn, is believed to have been caused by photosynthetic organisms drawing down the CO2 levels while spiking the oxygen levels (relatively speaking).  Yes, the snowball earth events are, like in the Eocene's Azolla Event, examples of biogenic climate change.

Within 100 million years of the end of the Snowball Earth complex life arose.  Except it would vanish from the fossil record, probably having gone extinct and changing the biological fate of the Earth.

Wait.  You thought I was talking about the Cryogenian and Ediacaran?

After all, the Cryogenian's Marinoan Glaciation (or maybe Sturtian or Kaigas), NeoProterozoic Oxygenation Event, Ediacaran with its biota and then Cambrian do parallel all of the above.  Except that complex life is obviously still around and the Phanerozoic is quite biologically diverse, to say the least.

But, no, despite the parallels, I am not talking about the rise of modern complex life.  Rather I am talking about events which took place more than a billion years earlier, during the PaleoProterozoic.

Oxygen, Glaciers and Complex Life, oh my!

There has been up talk of the Great Oxygenation Event.  This is when life puped out oxygen in sufficiently large quantities oxygen were poured into the atmosphere by photosynthetic life, namely something like the cyanobacteria.  This may have been one of the first mass extinctions because obligate anaerobes cannot survive in the presence of oxygen, for one, and for the second, it radically changed the climate.

By pulling down the carbon dioxide and releasing free oxygen, the cyanobacteria tipped the earth from a greenhouse climate to an icehouse climate.  This in turn, without the 'modern' feedback loops, turned into what is suspected to be the earliest Snowball Earth, during the Siderian and Rhyacian.  This glaciation, called the Huronian, lasted (as far as we can tell) for 300 million years, from the mid Siderian to about 50 million years before the end of the Rhyacian. 

In 2010, a remarkable find was brought to light from Gabon, Africa.  There appeared to be colonial, or even possibly true complex life in the Rhyacian.  Further study of the fossils strongly suggested they were some form of complex life.  However, strangely, not like our complex life which seems to have arisen piecemeal during the Cryogenian into the Ediacaran and exploded during the Cambrian.  The timing of the appearance of the Francevillian Biota

Reflections in the Mirror: Parallel Events, Evolution? | ?noitulovE, stnevE lellaraP

The Francevillian Biota has several biotic members.  Its easy to see some physical parallels between the Ediacaran Biota members and those above.  There are forms which are reminicent but not the same as the Edaicaran discoid, Dickinsonia and rangeomorph fossils.  They are not the same, by any means, but the suggested parallels are interesting.  No, I am not saying the Ediacaran forms evolved form the Rhyacian!  Quite the contrary!  Rather, I am suggesting there is an event of parallel evolution taking place.  Independently.  Form follows function.  However, this is more suggestively so than closely (unlike the classic of sharks, ichthyosaurs and dolphins), but what's even better of a parallel is the events which led up to the both the evolution of the Francevillian and Ediacaran Biotas.

The events of the two different time frames, Siderian/Rhyacian & Cryogenian/Ediacaran (global glaciations, O2 spike and the seeming rise of complex life) is pretty exciting.  Is this what it would take to have Earth-evolved life to produce complex life forms?  Perhaps.  Its worth looking into.  However, the huge question becomes, if complex life evolved 2.05 billion years why is there a hiatus for over a billion years.  Those years sometimes being called the Boring Billion (more properly, the MesoProterozoic).  During that time frame, we have evidence of microbial life, but nothing like an animal or plant.  So?  What happened?  It must have gone extinct.  There are two possible explanations, assuming this is in fact complex life in the Francevillian Biota.

One is the Francevillian Biota didn't produce a proper Gaia-like feedback system and they tipped over into a feedback loop which caused them to ruin their own environment.  Or rather they ran out of their nutrients.  Or failed to develop a self sustaining ecosystem.  Its a biological failure then.  Producing Gaia is hard.  At best its 50-50 proposition of true.

The second possible reason is even more compelling.  Why?  Because of the time and energy involved.  27 million years after the Francevillian fossils were deposited, one of the biggest asteroid impacts the Earth has seen since the Late Heavy Bombardment took place.  And 150 million years after that, a comparable asteroid smashed into the world.  Both of these impacts dwarf the Chicxulub Crater.

Say Hello to my Little Friend.  Ahem, BFG.  Twice.

It has already been established giant impacts can cause mass extinctions.  The impact in Chicxulub, Mexico 66 million years ago, wiped out 50% of life on the planet.  The KT or K-Pg Extinction made way for our modern ecology and our own evolution.  The Chicxulub impact was the equivalent of over 100 teratons of explosives, roughly over 1000 times the combined nuclear arsenals on Earth.  There are two impacts which followed the Francevillian Biota which were significantly more powerful.

The Vredefort Impact took place 'first.'   The astrobleme for Vredefort is in southern Africa and dates to 2.023 billion years ago.  The crater it left was 300 km in diameter: Chicxulub is 'only' 180 km in diameter.  The impact would have been significantly more energetic than Chicxulub.  This is guaranteed mass extinction.  In fact, its a significantly more devastating mass extinction because the Francevillian Biota is almost assuredly younger and less robust than when our lineage dating from the Cryogenian took it in the shorts from Chicxulub.  Had Chicxulub happened before the Cambrian Exoplosion, its probable there wouldn't be anything remotely complex on the planet.  Vredefort was worse.

As if Vredefort was not enough, 150 million years later, circa 1.849 billion years ago, came the Sudbury Impact.  It was of a comparable energy and bollide size. If any thing complex survived the Vredefort, which would be doubtful, the Sudbury almost assuredly finished them off.  The two impacts, btw, bracket the Orosirian Period.

Interestingly, a paper which just came out supports the scenario.  Although the authors are studying about two different impacts at an earlier time, they found geological evidence of the upper sea boiling from the devastation wrought.  The Sudbury and the Vredefort Impacts both have the potential to done the exact same thing.  Given the Francevillian Biota was a shallow water assemblage, its entirely likely they were wiped out in one or both of the events.

The surviving largely microbial life would trundle on in a relatively stable environment for another billion years thence.

Every Earth Deserves a Second Chance

Assuming the Francevillian Biota was, in fact, complex life, Earth would need another billion years until the Ediacaran to take another stab at complex life.  This time it would be successful and continue into the present, despite mass extinctions.  Fortunately, there have been no bollides of comparable mass or energy as the Vredefort or Sudbury since.  Their descendents are us.

The hypothesis we had extremely distant cousins makes for some interesting conjectures.

• Under the right stimulus, it seems complex life arises when working with earth evolved organisms.  However, it does seem to require those proper chain of events.  

• Additionally, as soon as life had a chance, it also appears to (inadvertently) triggered the events which led up to complex life.  This, in turn, suggests complex life may be common where it is possible to evolve.  

• However, it is also possible to wipe out complex life without requiring too crazy of events (or intelligent intervention).

• It seems likely Mars will definitely not have any traces of complex life.  If the Earth was still getting battered at 1.85 billion years ago, that is well past the point when Mars' atmosphere thinned.  Additionally, the Hellas Basin is an impact crater which is 2,300 km in diameter.  If Vredefort was tough, then Hellas was hell and the likelihood of anything surviving through that impact is almost nil.  The Hellas Impact took place ~3.8 billion years ago.  For that matter, the Argyre Planitia is also another impact basin and it is 1,800 km in diameter, if not as deep as the Hellas.  Its highly unlikely any life survived past these events.  There's a slim chance Earth could have reintroduced life, but by the time the Francevillian Biota arose, Mars had something akin to its present atmosphere.

The story outlined above, the hypothesis which I've hung out there in my first paleo post in some time, hangs together quite well in view of the science.  However, it needs to be tested.  We can only test the hypothesis by finding other locales similar to Franceville.  Likewise, a lot of detailed examination of the Francevillian Biota as known is needed. Likewise, deposits from after Vredefort and in similar paleoenvironmental conditions are needed from the Orosirian.  

Then what's needed is to understand why the MesoProterozoic didn't have any glaciations and, thus, did not produce the complex life as we (squintingly) know it earlier.

Extreme Shrimp as a Guide to Potential Europan Life?

link.

Kookiness in a Journal? Did Venera-14 Find Life?

Hypothetical flora and fauna of Venus

Author:

Ksanfomality

Abstract:

Hypothetical habitability of some of extrasolar planets is a fundamental question of science. Some of exoplanets possess physical conditions close to those of Venus. Therefore, the planet Venus, with its dense and hot (735 K) oxygen-free atmosphere of CO2, having a high pressure of 9.2 MPa at the surface, can be a natural laboratory for this kind of studies. The only existing data on the planet׳s surface are still the results obtained by the Soviet VENERA landers in the 1970s and 1980s. The TV experiments of Venera-9 and 10 (October, 1975) and Venera-13 and 14 (March, 1982) delivered 41 panoramas of Venus surface (or their fragments). There have not been any similar missions to Venus in the subsequent 39 and 32 years. In the absence of new landing missions to Venus, the VENERA panoramas have been re-processed. The results of these missions are studied anew. A dozen of relatively large objects, from a decimeter to half a meter in size, with an unusual morphology have been found which moved very slowly or changed slightly their shape. Their emergence by chance could hardly be explained by noise. Certain unusual findings that have similar structure were found in different areas of the planet. This paper presents the last results obtained of a search for hypothetical flora and fauna of Venus.

Was the Mitochondrial Ancestor a Parasite?

Phylogenomic Reconstruction Indicates Mitochondrial Ancestor Was an Energy Parasite

Authors:

Wang et al

Abstract:

Reconstruction of mitochondrial ancestor has great impact on our understanding of the origin of mitochondria. Previous studies have largely focused on reconstructing the last common ancestor of all contemporary mitochondria (proto-mitochondria), but not on the more informative pre-mitochondria (the last common ancestor of mitochondria and their alphaproteobacterial sister clade). Using a phylogenomic approach and leveraging on the increased taxonomic sampling of alphaproteobacterial and eukaryotic genomes, we reconstructed the metabolisms of both proto-mitochondria and pre-mitochondria. Our reconstruction depicts a more streamlined proto-mitochondrion than these predicted by previous studies, and revealed several novel insights into the mitochondria-derived eukaryotic metabolisms including the lipid metabolism. Most strikingly, pre-mitochondrion was predicted to possess a plastid/parasite type of ATP/ADP translocase that imports ATP from the host, which posits pre-mitochondrion as an energy parasite that directly contrasts with the current role of mitochondria as the cell’s energy producer. In addition, pre-mitochondrion was predicted to encode a large number of flagellar genes and several cytochrome oxidases functioning under low oxygen level, strongly supporting the previous finding that the mitochondrial ancestor was likely motile and capable of oxidative phosphorylation under microoxic condition.

Complex Life During the Rhyacian PaleoProterozoic From the Francevillian Biota

The 2.1 Ga Old Francevillian Biota: Biogenicity, Taphonomy and Biodiversity

Authors:

El Albani et al

Abstract:

The Paleoproterozoic Era witnessed crucial steps in the evolution of Earth's surface environments following the first appreciable rise of free atmospheric oxygen concentrations ~2.3 to 2.1 Ga ago, and concomitant shallow ocean oxygenation. While most sedimentary successions deposited during this time interval have experienced thermal overprinting from burial diagenesis and metamorphism, the ca. 2.1 Ga black shales of the Francevillian B Formation (FB2) cropping out in southeastern Gabon have not. The Francevillian Formation contains centimeter-sized structures interpreted as organized and spatially discrete populations of colonial organisms living in an oxygenated marine ecosystem. Here, new material from the FB2 black shales is presented and analyzed to further explore its biogenicity and taphonomy. Our extended record comprises variably sized, shaped, and structured pyritized macrofossils of lobate, elongated, and rod-shaped morphologies as well as abundant non-pyritized disk-shaped macrofossils and organic-walled acritarchs. Combined microtomography, geochemistry, and sedimentary analysis suggest a biota fossilized during early diagenesis. The emergence of this biota follows a rise in atmospheric oxygen, which is consistent with the idea that surface oxygenation allowed the evolution and ecological expansion of complex megascopic life.

Keep in mind Rettalack also claims complex terrestrial life in the Rhyacian PaleoProterozoic (100 million years after the critters from the above).

Vase-shaped Microfossils From Cryogenian Neoproterozoic Yukon, Canada

740 Ma vase-shaped microfossils from Yukon, Canada: Implications for Neoproterozoic chronology and biostratigraphy

Authors:

Strauss et al

Abstract:

Biostratigraphy underpins the Phanerozoic time scale, but its application to pre-Ediacaran strata has remained limited because Proterozoic taxa commonly have long or unknown stratigraphic ranges, poorly understood taphonomic constraints, and/or inadequate geochronological context. Here we report the discovery of abundant vase-shaped microfossils from the Callison Lake dolostone of the Coal Creek inlier (Yukon, Canada) that highlight the potential for biostratigraphic correlation of Neoproterozoic successions using species-level assemblage zones of limited duration. The fossiliferous horizon, dated here by Re-Os geochronology at 739.9 ± 6.1 Ma, shares multiple species-level taxa with a well-characterized assemblage from the Chuar Group of the Grand Canyon (Arizona, USA), dated by U-Pb on zircon from an interbedded tuff at 742 ± 6 Ma. The overlapping age and species assemblages from these two deposits suggest biostratigraphic utility, at least within Neoproterozoic basins of Laurentia, and perhaps globally. The new Re-Os age also confirms the timing of the Islay δ13Ccarbonate anomaly in northwestern Canada, which predates the onset of the Sturtian glaciation by less than 15 m.y. Together these data provide global calibration of sedimentary, paleontological, and geochemical records on the eve of profound environmental and evolutionary change.

Extraordinary Claim: A Gamma Ray Burst CAUSED the Cambrian Explosion?!

Did Gamma Ray Burst Induce Cambrian Explosion?

Authors:

Chen et al

Abstract:

One longstanding mystery in bio-evolution since Darwin's time is the origin of the Cambrian explosion that happened around 540 million years ago (Mya), where an extremely rapid increase of species occurred. Here we suggest that a nearby GRB event ~500 parsecs away, which should occur about once per 5 Gy, might have triggered the Cambrian explosion. Due to a relatively lower cross section and the conservation of photon number in Compton scattering, a substantial fraction of the GRB photons can reach the sea level and would induce DNA mutations in organisms protected by a shallow layer of water or soil, thus expediting the bio-diversification. This possibility of inducing genetic mutations is unique among all candidate sources for major incidents in the history of bio-evolution. A possible evidence would be the anomalous abundance of certain nuclear isotopes with long half-lives transmuted by the GRB photons in geological records from the Cambrian period. Our notion also imposes constraints on the evolution of exoplanet organisms and the migration of panspermia.

Plate Tectonic Influences on the Early History of Animal Evolution

Plate tectonic influences on Neoproterozoic-early Paleozoic climate and animal evolution

Authors:

Mckenzie et al

Abstract:

The initial diversification of animals paralleled some of the most dramatic episodes of climate and environmental change in Earth history. We compiled global Neoproterozoic-early Paleozoic detrital zircon age data to track spatiotemporal variations in continental arc systems to explore the influence of tectonic outgassing of CO2 on these climatic shifts. These data indicate that global continental arc systems were spatially reduced at the onset of the Cryogenian glacial interval, widespread during the Cambrian greenhouse, and reduced during Ordovician cooling. The Cambrian greenhouse was coincident with ecologically stressed conditions, whereas Ordovician global cooling was accompanied by a major biodiversification event. Thus, variation in the continental arc CO2 flux likely played a critical role in major climatic fluctuations, which profoundly influenced early animal evolution.

Playing God: Scientists Forcibly Evolve Multicellularity in Algae (Meanies!)

Scientists have puzzled for centuries over how and why multicellular organisms evolved the almost universal trait of using single cells, such as eggs and sperm, to reproduce. Now researchers led by University of Minnesota College of Biological Sciences postdoctoral fellow William Ratcliff and associate professor Michael Travisano have set a big piece of that puzzle into place by applying experimental evolution to transform a single-celled algae into a multicellular one that reproduces by dispersing single cells.

"Until now, biologists have assumed that this single-cell bottleneck evolved well after multicellularity, as a mechanism to reduce conflicts of interest among the cells making up the organism," says Ratcliff. "Instead, we found that it arose at the same time as multicellularity. This has big implications for how multicellular complexity might arise in nature, because it shows that this key trait, which opens the door to evolving greater multicellular complexity, can evolve rapidly."

In an article published today in the journal Nature Communications, the researchers described how they produced the multi-celled strain by repeatedly selecting and culturing algae that settled quickly to the bottom of a liquid-filled test tube. After 73 rounds, they discovered that the algae in one of the tubes had gone multicellular.

Observing the new form, Ratcliff and Travisano discovered that it reproduced by actively breaking up, shedding motile single cells that go on to grow into new multicellular clusters. They developed a mathematical model that explained the reproductive benefit of this single-celled strategy over hypothetical alternatives in which the cluster would produce larger propagules. The model predicted that reproduction from single cells would be more successful in the long run. Even though single cells are less likely to survive than larger propagules, this disadvantage is more than made up for by their sheer number.

In collaboration with Matthew Herron and Frank Rosenzweig at the University of Montana, the researchers are now working to find the genetic basis for multicellularity and experimentally evolve even greater multicellular complexity.

link.

Extraordinary Claim: Atmospheric Oxygen in Rhyacian PaleoProterozoic was Same as During the Cambrian Explosion

Any textbook will tell you that oxygen is essential for advanced life to evolve. For example, ancient dinosaurs and modern large-brained mammals need a lot of oxygen to keep their large and sophisticated organisms running. But why did life not explode when oxygen levels rose dramatically 2.1 billion years ago? This is the big question after a Danish/Swedish/French research team, led by University of Southern Denmark, has shown that the oxygen content 2.1 billion years ago was probably the same as when life exploded 500 million years ago.

Oxygen and advanced life are inextricably linked. Some simple organisms like bacteria can survive without oxygen, but all higher organisms need oxygen and the Earth's biology would probably be a poor sight, if the atmosphere did not contain the 21 pct. oxygen, which is essential for eg the human brain to function.

The development of life exploded around 542 million years ago during the so-called Cambrian explosion, where oxygen levels rose to up to 10 pct. Before that life consisted of small and simple, typically single-celled life forms, and science has long thought that there was not enough oxygen for it to evolve into something bigger.

But now a Danish/Swedish/French research team shows that there was actually plenty of oxygen long before the Cambrian explosion. The team consists of professor Donald Canfield and postdoc Emma Hammarlund from the Nordic Center for Earth Evolution (NordCEE) at University of Southern Denmark, colleagues from the National Museum in Sweden and colleagues from the following French institutions: Université de Poitiers, the Centre National de la Recherche Scientifique, Institut Francais de la Recherche pour l' Exploitation de la Mer, Centre de Brest and the Université de Rennes in France.

"We have examined rocks that are 2.15 billion - 2.08 billion years old. They show us that there was oxygen in deep water and thus also in the atmosphere at that time. We cannot say exactly how much, but there was probably ample oxygen and also ample time to permit advanced life to evolve", says Emma Hammarlund.

The same research team has previously demonstrated the existence of some strange fossils from the same place. The researchers interpret these fossils as a way of life that tried to evolve into a multicellular life form.

"It was not a life form that in any way is comparable to large life as we know it today. It was rather microbes that experimented with a way to evolve into some form of multicellular existence. It had enough oxygen for the experiment, but its destiny is unknows", she says.

One explanation may be that most traces of advanced, 2 billion year-old life is gone. If the life forms did not develop bones or shells, they would not easily be fossilized and found today.

"Currently we consider it more likely that any great evolution just did not occur then. But why not, since there was plenty of oxygen?", speculates Emma Hammarlund, and tries to answer:

"Perhaps the problem was with the genetics of the life forms. Or maybe the organisms did not try to eat each other, so an evolutionary race could get started. There are several options, but we just do not know enough about it yet".

The new discovery that there was plenty of oxygen in the atmosphere 2 billion years ago also contributes to a new understanding of the Earth's development. It shows that the content of atmospheric oxygen has taken several ups and downs. 250 - 300 million years ago oxygen content rose to up to 25 pct., and this led to the development of some enormous insects. But everything was not all good: The high oxygen content simply increased the chance for trees to ignite, so it was also a period of many wildfires. This has been revealed by layers of ash from that time.

link.

Did an Impact Cause the Shuram Event in the Ediacaran by Shifting the Earth's Axis?

Evolution of Earth's climatic system: Evidence from ice ages, isotopes, and impacts

Author:

Grant M. Young

Abstract:

Multiple glaciations took place near the beginning and end of the Proterozoic Eon. Neoproterozoic (Cryogenian) glacial deposits are more widespread than those of older (Paleoproterozoic) glacial episodes. Paleomagnetic results suggest that most Proterozoic glaciogenic rocks were deposited at low paleolatitudes. Some contain enigmatic evidence of strong seasonal temperature variations, and many formed at sea level. These attributes inspired both the snowball Earth hypothesis and the high obliquity theory, but only the latter explains strong seasonality at low latitudes. The Proterozoic glaciations may have been triggered by drawdown of atmospheric CO2 during enhanced weathering of elevated supercontinents. Multiple glaciations resulted from a negative feedback loop in the weathering system that ended when the supercontinent broke apart. A radical reorganization of the climatic system took place in the Ediacaran Period. In contrast to previous glaciations, these ice sheets developed in high latitudes and many follow mountain building episodes. During the Ediacaran Period, Earth’s climatic zonation and controls appear to have undergone a radical change that persisted throughout the Phanerozoic Eon. The change may coincide with the world’s greatest negative δ13C excursion, the Shuram event, here interpreted as the result of a very large marine impact that decreased the obliquity of the ecliptic, causing the Earth’s climatic system to adopt its present configuration. Attendant unprecedented environmental reorganization may have played a crucial role in the emergence of complex life forms.