Ancient Life

Ediacaran ancient life form Dickinsonia CostataThe history of ancient life on Earth is written in its oldest rocks.  Paleontologists, detectives who track the ancient denizens of that early world, continue to gather fossil evidence of the earliest multicellular life, the Ediacara.

These mysterious creatures preceded the famous Cambrian explosion that began 541 million years ago.

The Cambrian, abundant with the fossils from the ancient ocean sediments, including the Burgess Shale in Canada, justifiably captures the popular spotlight.

Trilobite from the Devonian

This little devil, a Devonian trilobite, was armed with an as-yet unexplained trident. Photo credit: Wikipedia

Almost everyone has seen a trilobite, an animal that appeared in the Cambrian and roamed the ancient seas for 270 million years, right up to the Permian-Triassic extinction, the so-called “Great Dying” 252 million years ago.  

Of course, even kids know the names of dinosaurs, which came to rule the Earth after the Great Dying until only 66 million years ago.

Ediacaran life has attracted much less celebrity

Beginning in the 1950s, a few fossils began to tell of complex animals that were not even supposed to exist prior to the Cambrian.  

This pre-Cambrian time, the Ediacaran period, between 575 and 542 million years ago, followed the Marinoan glaciation or “Snowball Earth,” a period when the entire surface of our planet was frozen solid.

Not that long ago, the Cambrian was considered the boundary before which no multicellular life existed.  That’s all changed.  

Simple one-celled life appeared on Earth about a billion years after the planet formed 4.5 billion years ago, a time punctuated by massive meteor bombardments, including a whopping collision with a Mars-sized planet that sent molten rock into space to form our Moon.

Ancient life may have originated at hot geothermal vents

White smokers at the Champagne vent, Northwest Eifuku volcano, Marianas Trench Marine National Monument Photo Credit: NOAA

Life Begins

Within less than a billion years life appeared. Life on Earth may have gotten its start near deep-sea geothermal vents, still the home of extremeophile bacteria and the animals that feed on them.    

Whatever process led to the emergence of life, soon single-celled plants began converting the Earth’s carbon dioxide into oxygen and carbohydrates, the stuff you sprinkle on your cereal.

The first oxygen was consumed by iron dissolved in the oceans which became iron oxide or rust, laid down as rich ore deposits later used to make your car.

ancient iron deposits

Dissolved iron in the oceans, which “rusted” when oxygen became plentiful, was deposited as banded ironstones.

The conversion of a carbon-dioxide in the Earth’s atmosphere into oxygen may seem like a good thing to mammals like us.  But carbon dioxide traps heat much better than does oxygen.  Simple plants made too much of a good thing!  Oxygen cooled the Earth.

Our planet froze into a Snowball Earth.  Several times. 

Why did ancient single-celled life dominate Earth for so long?

Appearing “only” a billion years after the Earth formed, single celled life took more than three billion years to begin forming more complex multicullular life forms during the Ediacaran Period about 600 million years ago.  Meditate on this time line.  

Notice how quickly simple life appears 4 billion years ago, at the end of meteor bombardment of Earth. Yet, it takes a full 3 billion years and longer for animals to finally appear.  Then, in less than a billion years, animals conquer the Earth, with vertebrate animals only making land in about the last third of a billion, and mammals like humans showing up very, very late to the party.

Geologic Clock of Earth Photo Credit: Wikipedia

Ancient life took its sweet time to go from single cells, around 4 billion years ago, to more complex multicellular plants and animals, during the Ediacaran period, about 45 million years before the Cambrian. Photo credit: Wikipedia

Some scientists think that low oxygen levels in the oceans 1.8 to .8 billion years ago kept life simple. Others believe that Snowball Earths caused, ironically, by plentiful oxygen in the atmosphere, delayed the appearance of complex life. However, some paleontologists continue to push back the time of the first animals. perhaps even before the last “Snowball Earth.”  In any case, the Cambrian is no longer the first word in multicellular life.

Ediacaran Ancient Life Finally Gets Some Respect

These ancient critters now have their own explosion, the Avalon Explosion, a rapid increase in the diversity of Ediacara body forms that preceded the Cambrian Explosion by 33 million years.  If 33 million years doesn’t sound like much, it’s a quarter the length of the dinosaurs’ reign and half as long as the Cenozoic, the Age of Mammals.

A Sample Collection of Ediacaran Life Forms

Unless noted all photo credits:  Wikipedia

Dickinsonia

Ediacaran ancient life form Dickinsonia Costata

Dickinsonia grew as big as bath mats and apparently lay flat on the sea bottom, possibly grazing on microbial mats.  The segments of the soft-bodied Dickinsonia have been described as liquid-filled chambers, something like an air mattress. First discovered by Reg Sprigg in 1946 in the Flinders Ranges of South Australia, apparently while eating his lunch, Ediacaran fossils were described in a paper submitted to, and rejected by, the journal Nature.

Charnia

Charnia an ediacara

Charnia was first discovered in 1957 in rocks in Charnwood Forest in central England by Tina Negus, a 15-year-old schoolgirl, but her geography schoolteacher ruled out the possibility of Precambrian fossils.  

Later, a schoolboy Roger Mason, who later became a geologist, brought the fossils to the attention of scientists.  Charnia lived attached to the sea bottom, too deep for sunlight to allow photosynthesis, suggesting that they absorbed nutrients directly from the seawater.

 

 CharniodiscusCharniodiscus arboreus

Also first discovered in Charnwood Forest, Charniodiscus was first discovered as only the circular base or holdfast that anchored the stalk and frond to the sandy sea floor. Similar to Charnia, the frond structure is different, although the source of nutrition for this an Ediacaran fossil was presumably similar. Two Charniodiscus forms have been found, one with a short stalk and fat frond, the other with a long stalk that held the frond 20 inches above the sea bottom. 

Eoandromeda 

Eoandromeda and Ediacaron fossil

Eoandromeda has eight radial spiral arms, spiraling either clockwise or counterclockwise.  A few dozen fossils are known, ranging from 1 to 4 cm in diameter.  This specimen from Australia has longer, more tightly coiled arms compared to Chinese Eoandrommeda. Photo credit: http://www.flickr.com/groups/complex_life/ 

 

Spriggina_flounensi_C

Spriggina

Named for Ron Sprigg, this segmented Edicaran organism reached about 3-5 cm in length and may have been a predator. Two rows of tough interlocking plates cover the bottom, while one row covers its top.  Its front segments are fused to form a head, which may have borne eyes and antennae.

These are but a sample of a growing collection of Ediacaran organisms.  Below is an artist’s conception of an Ediacaran garden

Ediacarans National Museum of History, Smithsonian Institution

The Ediacara appear to have become extinct before the celebrated hustle and bustle of the Cambrian.  Some suggest they are a “failed experiment” that left no descendents.  As objects of scientific study the Ediacara are an active field with a growing list of Ediacaran genera.

Here’s how the Earth’s continents changed from Ediacaran times. 

Scientific Picture Book of the Ediacarans

Highly rated, with foreword by Arthur C. Clarke, The Rise of Animals by five respected authors is considered the best account of Ediacaran life.  Organized by fossil location, the book includes an Atlas of Ediacaran paleontology.

Take a Peek

Even if you are just curious, the “Look Inside” button at Amazon offers a generous sampling of the Ediacaran “zoo,” with fossil photos and interpretations of how these strange organisms lived.

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12 Responses to Ancient Life

  1. Jeremy says:

    Just imagine what it looked like back in its day … the mind reels!
    Jeremy recently posted..Top 5 Resume Writing TipsMy Profile

  2. Barb says:

    Same here. very much fascinated by ancient life, ancient civilizations. Add extra terrestrial life. There should be more movies about life like ages ago!
    Barb recently posted..Guidelines for Upholstery and Couch CleaningMy Profile

  3. Interesting. I’ve always fascinated about the ancient life. I was even on the verge of becoming an archaeologist. lol
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  4. silver price says:

    This is an superb approach. Since life on earth was restarted from scratch roughly six times by the vaporization of the crust. Life must get seeded from outer space. It makes no sense to assume that for the first 10 billion years the universe did nothing and then four billion years ago developed life six separate times from scratch on this measly planet we call earth.
    silver price recently posted..No last blog posts to return.My Profile

  5. Whilst it is possible that the geological composition of Mars varies immensely from region to region the researchers believe that it is more likely that the differences arise through a process known as subduction – in which material is recycled into the interior. They suggest that the Martian surface was oxidised very early in the history of the planet and that, through subduction, this oxygen-rich material was drawn into the shallow interior and recycled back to the surface during eruptions 4000 million years ago. The meteorites, by contrast, are much younger volcanic rocks that emerged from deeper within the planet and so were less influenced by this process.
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  6. Karen Ong says:

    I really love history and reading this post is such important to me. I love how you post about our planet, and the beginning of life. I really love reading your post! Please continue posting article/blogs like this. Please do also check my blog at http://1-pestcontrol.com/

  7. Knut Holt says:

    Some of these organisms were probably the forefathers of cambrian lifeforms or related to those forefathers. The bilateral ones may be related to the diferent worm-like phyla or arthropoda. The discoid ones may be the first jellyfish formed cnidaria. The frondlike species looks like colonies of smaller radially symmetrical animals and may be polypoid cnidaria, related to corals or hydroids, but not yet with a hard scheleton. What is then left are those which are not radially or bilaterally symmetrical. These can be something quite different. They might belong to a now extingt kingdom, or perhaps they were mushrooms.

    • AstroGremlin says:

      Thank you for your thoughtful remarks, Knut. Yes, it’s possible the Ediacaran forms gave rise to later life, although some speculate that they were a “dead end” or failed experiment. The bilateral symmetry of the Dickinsonia and the Charnia is tempting to compare with that of later bilateral forms, although these primitive animals appear to have grown in a different way, adding cells onto their extremities instead of starting out as small, symmetrical babies. The frondlike structures definitely were solving similar problems for life, filtering or using osmosis to feed from the currents. Perhaps fossil “missing links” will be found to show which were the ancestors of more modern forms.
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  8. Rose says:

    Astro G,

    This was (is) truly a fascinating read. One of my brothers is a geophysicist and my father was an environmental engineer. As a child, I visited areas around South-Western Ontario (Canada) and Manitoulin Island where well-preserved fossilized remains can be found.

    I remember being taught that the trilobite was the ‘first form of life on earth’ – and yet (as you’ve documented so clearly) it goes back much further.

    Interesting to me is how some structures haven’t changed all that much . . looking at the leaf-like Charnia, I immediately compared that with our lungs (as a means of oxygen exchange). And, how interesting that the amount of oxygen in the air significantly impacted growth. It would appear that adaptations made were most dependent on survival . . and wow, what a long time for sexual reproduction to finally happen.

    The backbone remains (although some, do not have much of one – ha). Looking at us fleshy, seemingly defenseless human form – we sure could use some more protection nowadays. It occurs to me that we were meant to colonize (to help one another) and that (unfortunately) the prey and predator element still remains among us. We are slow to evolve to the point of helping each other live (and not harm others). Some would call this “survival of the fittest” while I view it as a human weakness.

    With your express permission, I’d like to add a Big Arrow link to your article here on mine (you visited already): Nerdy-chick disagrees with Stephen Hawking. You may recall that you pointed me to this fact: “Paleontologists have found evidence of another separate group of relatives, the Denisovans, in a cave in Siberia.”

    Keep ‘em coming, you make this enjoyable to learn,

    Rose (aka sousababy)

    • AstroGremlin says:

      Big Arrow link graciously accepted! My father was a geologist and I was interested to a degree in his work. But the story told in the rocks is a complex one, with folding uplifting, erosion, sedimentation — and so much time passing as it all happens at once. The story of ancient life seems a bit easier to follow. What’s exciting is that theories keep changing and new ideas spring up with exquisitely accurate measurements of atmosphere content, ocean elements, temperature — I guess it’s pretty complicated, too! I reported early on after the undersea vent life was discovered — I knew it would have consequences for astrobiology such as life under the ice on Europa. The vents have turned out to be quite important for life on Earth, especially during the three Snowball Earths. Well, and even bombardment — self sustaining vents in ocean depths make quite the bunker for life to weather storms of meteors blasting away at the surface.
      AstroGremlin recently posted..Ancient LifeMy Profile

  9. Phil says:

    Terrific post! I love history and reading about our planet, and life’s beginning. Truly though, I still think much of this is hypothesis and we are still trying to figure it all out. I think we will never really truly know how life really started.
    Phil recently posted..I will say a prayer for you today Boston.My Profile
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