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Life on Earth was nothing but slime for a ‘boring billion’ years

Evolution of life on Earth began about 3.5 billion years ago but it has not been a constant or continuous process. During the middle years of Earth’s history (1.8 billion to 800 million years ago), evolution…

Slime on Earth… that’s all there was for a billion years. www.shutterstock.com

Evolution of life on Earth began about 3.5 billion years ago but it has not been a constant or continuous process.

During the middle years of Earth’s history (1.8 billion to 800 million years ago), evolution stagnated. Life remained as little more than a layer of slime for a billion years. This period has become known as the “boring billion” years.

So what was going on? A research team led by geologists at the University of Tasmania has developed new mineral technology to track the trace metal content of the ocean and oxygen content of the atmosphere over the past 3.5 billion years. This has never been achieved before.

Why is it important? Evolution of life in the oceans is strongly influenced by trace metals, as many metals (such as copper, zinc, cobalt and selenium) are taken up by marine species and are critical for life and evolutionary change.

Studying the ocean floor

Our UTAS research team – of which I was a part – with help from many other international geologists, have been collecting seafloor sediments from all around the world over the past six years.

Ross Large and Valeriy Maslennikov (from the Russian Academy of Science) on location in Siberia. Ross Large

We found pyrite (iron sulfide) in each sample and analysed for 22 different trace metals with a cutting edge laser system at UTAS, and built a unique database of more than 3,000 pyrite laser analyses to track changes in ocean chemistry spanning a 3.5-billion-year period through time.

Some exciting and totally unexpected outcomes emerged from this ocean tracking technology. The most significant outcome relates to how trace metals in the oceans have influenced the evolution of life.

Back in the early part of Earth’s history, from 3.5 billion to 1.8 billion years ago, single celled life evolved slowly but progressively, related to an abundance of available trace metals in the oceans. But during the “boring billion”, from 1,800 million to 800 million years ago, evolution slowed. This has been a puzzle to scientists.

Ocean life nearly collapsed

Our research, published in the Earth and Planetary Science Letters, suggests that the reason for the slow down is that the trace metal content of the oceans declined. This resulted in a depletion of critical trace metal nutrients to the point that oxygen content dropped and life in the oceans was in great danger of total collapse.

But rather than causing a mass extinction, marine life and evolutionary change was put on hold for a billion years.

Following the boring billion, our research shows that the trace metal content in the oceans rose steeply in a series of steps over a 200-million-year period, from 750 million to 550 million years ago.

This was accompanied by a steep rise in oxygen in the atmosphere (known as a Great Oxidation Event, see below) that led to the Cambrian explosion of life and progressive evolution to the present time.

The essential trace elements

Bio-essential trace elements are critical to life and evolution. These include cobalt, selenium, copper, zinc, molybdenum, vanadium and cadmium. Certain species need these trace elements to survive.

The elements are linked into the chemical structure of the cells and become a natural nutrient for survival. Cobalt is a central atom in the structure of vitamin B12, whereas zinc is essential for growth in many species.

The UTAS research team showed that at certain periods of earth history these trace elements were in short supply (such as the boring billion period) leading to evolutionary decline, whereas in other periods the bio-essential elements were in great abundance, causing rapid evolutionary change.

The Cambrian Explosion

The Cambrian explosion was the relatively rapid appearance, around 542 million years ago, of most major animal phyla, as demonstrated in the fossil record.

Fossil tracks form the Cambrian explosion. Flickr/Maitri, CC BY-NC-SA

This was accompanied by major diversification of other organisms. Before about 580 million years ago, most organisms were simple, composed of individual cells occasionally organised into colonies.

Over the following 70 million or 80 million years, the rate of evolution accelerated by an order of magnitude and the diversity of life began to resemble that of today.

The Cambrian explosion has generated intense scientific debate. The seemingly rapid appearance of fossils in the “Primordial Strata” was noted as early as the 1840s. In 1859 Charles Darwin discussed it as one of the main objections that could be made against his theory of evolution by natural selection.

The long-running puzzlement about the seemingly abrupt appearance of the Cambrian fauna 540 million years ago centres on three key questions:

  • was there really a mass diversification of complex organisms over a relatively short period of time during the early Cambrian, and are we lacking evidence of what really happened?
  • what might have driven such rapid change – was it all due to rising oxygen?
  • implications about the origin and evolution of animals?

This latest research by the UTAS team demonstrates, for the first time, a rapid increase in bio-essential trace elements in the ocean starting 660 million years ago. So was this the cause of the Cambrian explosion of life?

Great Oxidation Events (GOEs)

GOEs are large increases in oxygen in the Earth’s atmosphere and there have been two in Earth’s history – one at 2.4 billion to 2.5 billion years ago and one at around 700 million to 550 million years ago corresponding with the Cambrian Explosion.

There are several schools of thought about GOEs' origin. The most favoured theory is that the GOEs are produced by a dramatic increase in ancient marine organisms (cyanobacteria) that released oxygen as a by-product of photosynthesis.

But which came first? Did the increase in oxygen speed up evolution of life or did an increase in life result in a rapid rise in atmosphere oxygen?

Either way, the oxygen did eventually accumulate in the atmosphere, providing a new opportunity for biological diversification as well as tremendous changes in the nature of chemical interactions between the atmosphere, rocks, oceans and living organisms.

The research team at UTAS, using a novel approach to the problem, demonstrated major changes in trace element concentrations in the ocean at both GOEs, which may be the answer to the rapid expansion of life.

This is the start of a new journey for the Tasmanian research team and we will be doing much more with this technology.

But it’s already becoming clear that there have been many fluctuations in trace metal levels over the millennia and these may help us understand a host of events including the emergence of life, fish, plants and dinosaurs, mass extinctions, and the development of seafloor gold and other ore deposits.

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33 Comments sorted by

  1. Alex Cannara

    logged in via LinkedIn

    Very nice!

    And, to see an effect of the first GOE, look up Oklo Gabon natural reactors.

    Oxygen allowed many metals to become soluble oxides, including Uranium, At the time of the 1st GOE, Uranium was 'enriched' about as much as we now have to do to exploit U235 fission. So Ma Nature invented fission reactors in the mountains of West Africa, because of previous photosynthesis and bacterial concentration of Uranium oxide that formed later deposits.

    Nuclear fission, even production of Plutonium, is quite natural.
    ;]

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    1. Peter Campbell

      Scientist (researcherid B-7232-2008)

      In reply to Alex Cannara

      For that matter fusion is quite natural too - that hot bright thing that appears in the sky each morning - fortunately at a relatively safe distance.
      Yes, there is nothing benign about nature. It does not care whether we foul our nest or not, but we might care about the effects on our society and children.

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  2. John Newlands

    tree changer

    From time to time there are proposals to tax oxygen consumption. Without an oxygen rich atmosphere coal, oil and gas would be useless. However those fossil fuels represent atmospheric CO2 that was reduced by photosynthesis to burnable fuels a lot more recently than a billion years ago. I guess the slime set if up for land plants and more advanced plankton to continue the job.

    This fluke event must be rare in the universe. On Earth we had over a billion years of slow preparation of the atmosphere. Then like fleas sucking the blood of a healthy dog humans came late on the scene and burned all the reduced forms of carbon they could dig up. That is happening perhaps a million times faster than those fuels were created. Now that process looks troubled due to depletion and waste products a.k.a. climate change.

    No doubt the Earth will still be here in another billion years probably without humans. Slime will rule once again.

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    1. Mike Swinbourne

      logged in via Facebook

      In reply to John Newlands

      I'm not sure if slime will rule again John, but there is no doubt that the current climate change caused by the inhabitants of the Earth has happened before, but in the opposite way, as the cyanobacteria soaked up all the CO2 and replaced it with oxygen.

      Anyone who thinks that we can't alter the atmosphere enough to cause climate change doesn't know their history. We wouldn't be here if it hadn't happened before.

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    2. Doug Hutcheson

      Poet

      In reply to John Newlands

      John, "This fluke event must be rare in the universe". I'm not sure if this is true, given the mind-boggling size and star population of the universe we can see. Even if it is unusual, sheer weight of numbers suggests it has happened before and will happen again. That's why, when I look up at the night sky, I wave.

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    3. Kelly Web

      logged in via Facebook

      In reply to Doug Hutcheson

      author's research add anything to previous work which identified high levels of mercury in sedimentary rocks dating from the time of the Permian extinction, and which has been suggested as a cause of that event?
      <a href="http://www.serverhdd.com/">kelly</a>;

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  3. Comment removed by moderator.

  4. Malcolm Robinson

    Geologist

    Does the author's research add anything to previous work which identified high levels of mercury in sedimentary rocks dating from the time of the Permian extinction, and which has been suggested as a cause of that event?

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    1. Ross Large

      Distinguished Professor of Geology at University of Tasmania

      In reply to Malcolm Robinson

      Malcome,

      We are working on marine sediments from the Perth Basin in WA at the Permian Triassic boundary. We have found exceptionally high levels in nickel in the sedimentary pyrite at the boundary. This supports the theory that the Siberian Trap Volcanic mega-eruptions were the cause of the mass extinction. These eruptives are associated with the worlds largest nickel deposits, It appears that the worlds oceans became polluted in nickel at that time. We are writing a separate paper on this issue. But we have found no enrichment in mercury at the end Permian.

      Ross

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  5. John Pickard

    Eclectic naturalist

    Very nice article, thanks Ross.

    Of course, you missed the obvious exceptions to evolution: the slimes that have persisted and are now politicians! Yeah I know, what do I have against bacterial slimes that helped the GOE???

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  6. Doug Hutcheson

    Poet

    Ah, the good, old Primordial Slime - I remember it well (oops - am I showing my age?) ...

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  7. Ulises

    logged in via Twitter

    But, is there evolution if there is no time? How will evolutionary biology meet new physical paradigms about time, space and so on? Will new conceptual changes deny evolution? Or on the contrary, will it become a more extraordinary process, full of astonishing implications? If so, will past human beings and the rest of living beings become different as science progresses? After all, is life something fix-finite-defined? That is, can one understand it by means of using a brain and its limited words? Does the whole of life fit into a bone box? Indeed, will science add indefinitely without understanding completely? Anyway, is it possible to understand something completely? Along these lines, there is a different book, a preview in http://goo.gl/rfVqw6 Just another suggestion

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  8. James Hill

    Industrial Designer

    As an interesting adjunct this article, and the good old primordial slime that persisted for a Billion years, is some thing from The Myths And Tales Of The Cymry, from the "Celtic" book in the Myths and Legends Series.
    The author, realising that the beliefs of the ancient Celts are practically extinct nevertheless thinks it important to describe in that book a work of considerable philosophic interest (which includes said primordial slime).
    It is Druidic, according to the author and represents…

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    1. James Hill

      Industrial Designer

      In reply to James Hill

      Correction: Was this the ancient bardic teaching of the Druids on evolution?

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  9. Comment removed by moderator.

  10. David Semmens

    logged in via Twitter

    A really fascinating article.

    Although, I have a nit to pick about the characterisation of evolution. The article implies, if inadvertently, that evolution progresses toward complexity and that because conditions prevented the emergence of complex life, evolution had stagnated. But this is not so. Evolution during the boring billions was most likely progressing no differently to today; with the 'slime' undergoing diversification and speciation at the same pace as modern microbial life.

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    1. Dianna Arthur
      Dianna Arthur is a Friend of The Conversation.

      Environmentalist

      In reply to David Semmens

      Which is why there are still slime moulds today - they diversified enough to adapt to the changing conditions.

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    2. David Semmens

      logged in via Twitter

      In reply to Dianna Arthur

      Slime moulds are actually complex life. But there are a huge number of microbes around today. Microbes are far, far more diverse than complex life.

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  11. Peter Boyd Lane

    geologist

    A most interesting article. One reason I did geology was that I wasnt very good at chemistry, so could you please explain the relationship between photosynthesis, atmospheric oxygen and oceanic oxygen (especially the last two)?

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  12. Peter Yard

    Software Developer / Technnical Writer

    Thank you. A very interesting article. I can't help but indulge in some wild eyed speculation about it. 660 million years ago is about the time of Snowball Earth, is this a coincidence or could it be that the abnormal conditions also released a lot of trace elements into the oceans as a result? Glaciers everywhere grinding up rock into dust, then followed by thawing and flushing the dust to the sea ... then life blooms.

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    1. Ross Large

      Distinguished Professor of Geology at University of Tasmania

      In reply to Peter Yard

      Yes there were three glaciation events in the period 750 to 550 million years ago when the O2 levels (based on our data) were rising from a low period around 800 Ma to a peak around 520 Ma. The glaciation events are thought to relate to periods of low atmosphere CO2 which caused global cooling. The general wisdom is that major ice cover of the continents reduces erosion and thus less nutrients into the oceans. But your suggestion of glaciers grinding up rock and releasing traces is a reasonable alternative. Whatever the scenario it seems that both nutrients in the ocean and O2 in the atmosphere rose over about 200 million years, but probably with perturbations around the three glacial events.

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  13. Peter Lang

    Retired geologist and engineer

    Very interesting article. Thank you. And congratulation to you ant The Conversation's editors for posting real science with no eco-religious prejudice.

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  14. Peter Lang

    Retired geologist and engineer

    Some may not be aware of the fantastic opportunity they have to take a 20 km drive down Brachina Gorge in the Flinder's Ranges and view a complete, unbroken history from 680 to 540 million years ago. That is from just before the last "Snowball Earth" to the Cambrian Explosion.

    It's a great, 1 day trip down the gorge and there are excellent signs describing the age and name of each layer as you drive along. You can walk down into the dry creek bed to see the rocks exposed, and fossils once you…

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  15. Steven Waters

    logged in via Facebook

    Give me a break. A fluke event and talking about all these circumstantial scenarios that may have happened like its some science fiction story. The one thing no one is mentioning is the thousands of complex stages many of which cannot happen unless they happen together and at the same time as one is dependent on the other. In fact one the great origins of life scientists put it this way.

    Dr. Robert Shapiro: was professor emeritus of chemistry at New York University. He is best known for his work…

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    1. Terry J Wall
      Terry J Wall is a Friend of The Conversation.

      Still Learning at University of Life

      In reply to Steven Waters

      Steven, thanks for your comment but my life experience shows quite the reverse. I feel that nature has sorted it out as is evidenced but those living in a high mineral environment, both from the animal and human experience.

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  16. Terry J Wall
    Terry J Wall is a Friend of The Conversation.

    Still Learning at University of Life

    Well there you go! A rise in the levels of trace minerals (metals or whatever) has now been shown to by research to be directly related to an increase in the power and diversity of life on this planet.
    Then it won't be long before the link between this discovery (which I can assure you will be spot on) and the fact that we now live deficient of these life force elements (due to acid rain et al) just might not be to good for humanity and is likely to be leading to a steady downward pressure on our ability to perform as we might?
    Or to go a step further, great minds may soon realize that boosting our intake with an naturally balanced range of organic trace minerals may have some potential to lift those so enlightened to where we might go!

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  17. Albert Rogers

    logged in via Facebook

    I do not believe for a moment that any of those slime beings were bored.

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  18. Albert Rogers

    logged in via Facebook

    The most interesting years are the ones that left no evidence at all.There must have been an evolution of the complex biochemicals that no are essential to all living organisms, and competition of some sort among them that left "our lot" the sole survivor. Even the shared code that translates three-base codons into amino acid specification has been shown to be arbitrary, but common to us all, even the Archea.

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