New study challenges old views about evolution of early life

Dec 23, 2012
Organic-rich shale samples, such as these from the 2.5-billion-year-old Mount McRae Shale from Western Australia, were analyzed for their zinc contents. The results confirm that the early ocean was not Zn-lean and that other controls must be invoked to explain the protracted appearance and proliferation of eukaryotic life. Credit: Arizona State University

A research team led by biogeochemists at the University of California, Riverside has tested a popular hypothesis in paleo-ocean chemistry, and proved it false.

The fossil record indicates that eukaryotes—single-celled and with more complex compared to prokaryotes, such as bacteria—show limited morphological and before 800-600 million years ago. Many researchers attribute the delayed diversification and proliferation of eukaryotes, which culminated in the appearance of complex animals about 600 million years ago, to very low levels of the zinc in seawater.

As it is for humans, zinc is essential for a wide range of basic . Zinc-binding proteins, primarily located in the , are involved in the regulation of .

Eukaryotes have increasingly incorporated zinc-binding structures during the last third of their evolutionary history and still employ both early- and late-evolving zinc- structures. Zinc is, therefore, of particular importance to eukaryotic organisms. And so it is not a stretch to blame the 1-2-billion-year delay in the diversification of eukaryotes on low bioavailability of this trace metal.

But after analyzing marine black shale samples from North America, Africa, Australia, Asia and Europe, ranging in age from 2.7 billion years to 580 million years old, the researchers found that the shales reflect high seawater zinc availability and that zinc concentrations during the Proterozoic (2.5 billion to 542 million years ago) were similar to modern concentrations. Zinc, the researchers posit, was never biolimiting.

Study results appear online Dec. 23 in Nature Geoscience.

"We argue that the concentration of zinc in ancient marine black shales is directly related to the concentrations of zinc in seawater and show that zinc is abundant in these rocks throughout Earth's history," said Clint Scott, the first author of the research paper and a former UC Riverside graduate student. "We found no evidence for zinc biolimitation in seawater."

Scott, now a research geologist with the U.S. Geological Survey, explained that the connection between zinc limitation and the evolution of eukaryotes was based largely on the hypothesis that Proterozoic oceans were broadly sulfidic. Under broadly sulfidic conditions, zinc should have been scarce because it would have rapidly precipitated in the oceans, he explained.

"However, a 2011 research paper in Nature also published by our group at UCR demonstrated that Proterozoic oceans were more likely broadly ferruginous—that is, low in oxygen and iron-rich—and that sulfidic conditions were more restricted than previously thought," said Scott, who performed the research in the lab of Timothy Lyons, a professor of biogeochemistry and the principal investigator of the research project.

The research team argues that ferruginous deep oceans, combined with large hydrothermal fluxes of zinc via volcanic activity on the seafloor, maintained high levels of dissolved zinc throughout the oceans and provided a relatively stable marine reservoir of the trace metal over the past 2.7 billion years.

"The key challenge in understanding the early evolution of life is recognizing the environmental conditions under which that life first appeared and diversified," Lyons said. "We have taken a very direct approach that specifically tracks the availability of essential micronutrients, and, to our surprise, zinc supplies in ancient seawater were much higher and less variable than previously imagined.

"We can imagine for the first time," he quipped, "that zinc supplements were not on the shopping lists of our early eukaryotic ancestors, and so we better find another reason to explain the mysterious delay in their rise in the ocean."

Explore further: Molecular gate that could keep cancer cells locked up

Related Stories

Zinc lozenges may shorten common-cold duration

Jul 26, 2011

Depending on the total dosage of zinc and the composition of lozenges, zinc lozenges may shorten the duration of common cold episodes by up to 40%, according to a study published in the Open Respiratory Medicine Journal.

Zinc lozenges may shorten common cold duration

Aug 16, 2011

Depending on the total dosage of zinc and the composition of lozenges, zinc lozenges may shorten the duration of common cold episodes by up to 40%, says Dr. Harri Hemila from the University of Helsinki.

Pneumonia wonder drug: Zinc saves lives

Feb 08, 2012

Respiratory tract infections, including pneumonia, are the most common cause of death in children under the age of five. In a study looking at children given standard antibiotic therapy, new research published in BioMed Central's ...

Recommended for you

Molecular gate that could keep cancer cells locked up

8 hours ago

In a study published today in Genes & Development, Dr Christian Speck from the MRC Clinical Sciences Centre's DNA Replication group, in collaboration with Brookhaven National Laboratory (BNL), New York, ...

The 'memory' of starvation is in your genes

11 hours ago

During the winter of 1944, the Nazis blocked food supplies to the western Netherlands, creating a period of widespread famine and devastation. The impact of starvation on expectant mothers produced one of the first known ...

Sugar mimics guide stem cells toward neural fate

Jul 30, 2014

Embryonic stem cells can develop into a multitude of cells types. Researchers would like to understand how to channel that development into the specific types of mature cells that make up the organs and other structures of ...

User comments : 15

Adjust slider to filter visible comments by rank

Display comments: newest first

jsdarkdestruction
4.6 / 5 (9) Dec 24, 2012
Kevin, this doesnt support your assertion the earth is 6000 years old.(a preemtive strike)
Torbjorn_Larsson_OM
5 / 5 (7) Dec 24, 2012
One obvious alternative, since we see currently see archaea and eukaryotes in the fossil record first after the atmosphere oxygenation at this time, is that diversification into the main clades happened after large scale oxygen stress was in place.
FrankHerbert
3.4 / 5 (10) Dec 24, 2012
At least Christmas gets Kevin out of our hair for a few days.
Shinobiwan Kenobi
1.7 / 5 (6) Dec 26, 2012
Kevin, if no one living is 6000 years old how do we know for certain that the assumption that biblical text is true? Surely these assumptions based on accounts by people that never observed first-hand what they are chronicling cannot be trusted to be accurate and we should question all of the books for the passages expoused may have been altered by translators or one of the many orators of the tales before they were written. (a preemtive rebuttal to Kev's rebuttal)
Torbjorn_Larsson_OM
4.2 / 5 (5) Dec 26, 2012
To pile on, creationists never makes sense.

But we can observe that their idea that childish unconstrained pointing at everything and go "gods did it" is their most Not Even Wrong (NEW) idea. It is for ever unpredictive because you can't test it. Hence it can't explain anything, despite making the unsubstantiated claim to explain "everything".

And that tomfoolery is closely followed by their NEW idea on empirical observation. Plural of anecdote ins't data, and again we demand constraints and their testing to ascertain the uncertainty of an observation against mutually agreed on quality limits. So again no substance and quality, and above all no empiricism.

Take the dating of the Earth as an example. It is a continuing, pervasive and generic observation of the geological record by certain radioisotopes that "were there" and more importantly still is there, sees the age as it grows. It is fully constrained (well, near enough for no difference) and testable as many times as we wish.
Torbjorn_Larsson_OM
3.6 / 5 (5) Dec 26, 2012
[cont] Last I heard the error range in observing Earth's age is down below to 100 000 years total, or less than the age of our own species of some 100 - 200 000 years, on a truly cosmological scale. (As Earth is ~ 1/3 of our universe's age.)

[Ironically we can, of course, test the reverse, the fully constrained observation that "gods didn't do it". It is written all over the CMB sky that "this universe is entirely made by nature", as inflation led up to the big bang universe we know and love. The CMB is an observation of inflation and a test of the 0 energy cosmology of FRW universes both.

Meaning we now *know*, less than a decade old knowledge, that no outside action can "create" a universe, or it wouldn't be 0 energy.

It has to arise spontaneously (Hawking), as a singleton or many times over, or existed always as a multiverse, with infinite many universes within, because it can (Susskind).]
Birger
5 / 5 (1) Dec 27, 2012
Kudos to Torbjörn Larsson and his comment!
Sonhouse
5 / 5 (2) Dec 28, 2012
Poor old Kevin, he can't get a word in edgewise:)
Shinobiwan Kenobi
1.7 / 5 (6) Dec 28, 2012
Poor old Kevin, he can't get a word in edgewise:)


It would probably help if the words he's already gotten in weren't simply variations on a theme.

...admittedly, it would have been more difficult for me to parody his argument.
Mikegyver
2.3 / 5 (3) Dec 28, 2012
Preemptive help for Kevin:

Fellas, come on now. This article is scientific evidence that there is a problem with the current understanding of evolution. Science simply cannot adequately explain how life started and how it overcame obstacles as indicated in this article.

So why bash someone who comes to the conclusion that life was created? If that's his conclusion, then that's his right. It isn't outside of science until proven otherwise.

Is the earth older than 6,000 years old? Of course it is, and it's a false assumption made by people who don't understand the bible. Don't attack that point and think you are doing someone a favor.

Until science undoubtedly proves every little theory, then you can't dismiss the possibility of God. To do so would be unscientific and you would be no better than the people you deem as religious idiots.
Modernmystic
1 / 5 (3) Dec 28, 2012
"Because there is a law such as gravity, the universe can and will create itself from nothing."


-Stephen Hawking

Sorry Dr. Hawking your postulate is invalidated by its own axiom. The "law of gravity" is indeed something. How can someone so brilliant be so ignorant?

Now the postulate that something has always existed is at least possible and is quite likely. This rubbish about spontaneous creation from nothing simply can't be consistent in any way.
Shinobiwan Kenobi
1 / 5 (5) Dec 28, 2012
Preemptive help for Kevin:

Fellas, come on now.


I feel that this point would be better served if any of Kevin's detractors showed up in the middle of Sunday service and started quoting research that shows that the dimensions given for Noah's Ark are by no means adequate for two of every animal and the necessary sustenance for all aboard said ark, but, I doubt any of us has this desire; why is it that prosetylism should be welcomed on a site that diminishes the need for superstitious explanations of natural phenomena?
Mikegyver
3 / 5 (2) Dec 28, 2012
...why is it that prosetylism should be welcomed on a site that diminishes the need for superstitious explanations of natural phenomena?


It should be allowed to exist here because the argument is science vs science here with the conclusion that science can't explain life.

If Kevin's detractors showed up in church it would be unfair because it is science vs a historical document. The bible is full of inaccuracies and to say "well, technically every living animal couldn't be on that boat because...". All that would prove is that the bible isn't 100% accurate. The dimensions could be off or it could have meant "all the animals in Noah's area" or something like that. Big deal. If the flood happened or if animals boarded the ark or not isn't relevant because it is just story.

Kevin's usual point here is that there seems to be something missing in the scientific viewpoint of evolution. That is science vs science. His conclusions that there might be a God makes sense here.
Shinobiwan Kenobi
1.6 / 5 (7) Dec 30, 2012
Kevin's arguments are not science vs. science, they are creationism vs. reality, his usual point is that unless something is directly observed by a person than we should question the validity of the work; I cannot tell you how many posts I have seen Kevin hop on decrying carbon dating be cause no human lives long enough to observe the decay of C14, or some variation against a well established principle in cosmology being BS because human life-spans are too short. I bring up Noah's ark specifically but the point is to address Kevin's generalizations which attempt to dismiss sound science but would not exist as an avenue of falsification if he would bother learning more about the subjects beyond his superficial surface scratchings.

As for proving the Bible is full of inacurracies, you're right, you don't have to go very far to do it. That is the larger point in creationism vs. reality, (cont)
Shinobiwan Kenobi
1.7 / 5 (6) Dec 30, 2012
(cont)

too many Bible-thumping-rubes (mostly in the U.S.) take what is written as immutable fact rather than a collection of metaphors, allegory, and elucidations upon human archetypes to strive for providing a blue print for moral behavior for those without the sense to figure out right and wrong without the threat of accountability meted out by a higher authority.

Many here have seen his rants, and many have humored him by engaging him; he is not here to better understand science, he is looking for ammunition against it.