What did life on earth look like 4 billion years ago? This photo shows fossil-like rock found in Australia containing hints of life from 4.1 billion years ago. Life on a near primordial Earth may have been around 4.1 billion years ago, 300 million years earlier than thought, hints a chemical fossil-like rock found in Australia. It also gives more hope for life elsewhere in the universe. (Bruce Watson/PNAS/AP)
What did life on earth look like 4 billion years ago?
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Scientists have found fossil-like hints that some kind of life existed on Earth 4.1 billion years ago. Back then the planet was a mere volcanic toddler. That's 300 million years earlier for life to pop up than previously thought.
 
Not only does that change the way scientists thought Earth was like soon after it formed 4.5 billion years ago, but it also gives them reason to theorize that life itself is more plentiful throughout the universe. That is because it seemed to start up so quickly.
 
Researchers examined tiny grains of the mineral zircon. It is found in western Australia's Jack Hills. The scientists chemically dated them to when Earth was barely 400 million years old. Inside one of the grains, they found what they call a "chemo-fossil."  It is a certain mix of carbon isotopes. This is according to a study published in the journal Proceedings of the National Academy of Sciences.
 
Think of it as "the gooey remains of biotic life or anything more complicated," said study co-author Mark Harrison. He is a UCLA geochemistry professor.
 
There are different types of carbon with different weights. This carbon residue had a higher percentage of the lighter type of carbon.  It's what scientists usually find in remnants of life. Think of it as the same as if your finger decayed, Harrison said. There are rare cases where this particular carbon signature wouldn't be from life. But they are exceedingly unusual and only in certain situations.
 
Harrison theorizes that the carbon is from a colony of tiny organisms of some unknown type. Life existing 300 million years earlier than science thought is the most logical and simplest explanation. But "this is not smoking gun evidence," Harrison said.
 
The common thinking of early volcanic Earth is that it was too molten.  The belief has been that there was not enough liquid water for life to take hold this early. But, Harrison said, there's no physical evidence for this theory. What the zircon shows is "the Earth by 4.1, 4.2 billion years ago was basically behaving like it is today."
 
"This is what transformative science is all about," said Stephen Mojzsis. He is a University of Colorado scientist who wasn't part of the research. "If life is responsible for these signatures, it arrives fast and early."
 
S. Blair Hedges of Temple University also wasn't part of the study. The professor said Harrison's findings make sense. The accelerated timeline of life fits with his own genetic tracking work.
 
"If life arose relatively quickly on Earth," Hedges wrote in an email, "then it could be common in the universe."

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CRITICAL THINKING QUESTION
Why does the presence of water factor into scientists thinking about life on earth?
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COMMENTS (55)
  • annabel1226-yyca
    10/26/2015 - 08:33 p.m.

    Yeah, what did the Earth looked like 4 billion years ago? Was it hard for us to breath in Earth? I think there wasn't dinosaurs before then. 4 billion years was a huge number for kids. Was the Earth cool and had more natural resources than today. I hope so because we used all the natural resources because humans are forming more humans. I think we have to much humans in Earth. I think Earth was the best natural resources for humans back than too. I hope I could learn more about Earth. I love Earth because it provides everything for me.><

  • ryan0420-yyca
    10/26/2015 - 09:02 p.m.

    I think that the earth was a big ocean and formed the curves and sand on earth.I also think that there was life before us because there are 10 billion of planets that are out there and we never know what is out there. We would never be a hundred percent corrcet on saying earth was formed because we weren't there 4 billion years ago.

  • zeusr-3-bar
    10/27/2015 - 02:00 p.m.

    that maybe this one animal died because there wasn't
    water to help this animal survive.

    so the earth has more life than expected.

    I wonder how this can affect man kind?

  • colek-1-bar
    10/27/2015 - 05:33 p.m.

    The presence of water shows that Earth might have had more early life forms that scientists have thought. This comes to show how little we know about our planets history. I found this article interesting and surprising that scientists have found even older life forms on earth.

  • paxtonc-jen
    10/28/2015 - 02:44 p.m.

    I love science. and this give so many facts about earth. Its really interesting and amazing.

  • samuelk-jar
    10/28/2015 - 02:45 p.m.

    This is kind of cool to learn about some stuff that took place on our planet 4.5 billion-300 million years ago.

    It was believed that life on earth started around 4.5 billion years ago, but we researched and studied and searched for clues and fossil's, used evidence, and with all that and the evidence that these scientists found, it was told that life on earth 300 million year earlier than we had thought.

    ~Sam K

  • peterw-jar
    10/28/2015 - 03:01 p.m.

    I liked to learn how the scientist found that fossil.I thought that it was cool how they came up with all these explanations how the earth was 4 billion years a go. They came up with there was not enough water for life to exist. This text was a good information sours and reliable and cool to learn about.

  • hollyh-1-jar
    10/28/2015 - 03:01 p.m.

    I thought that this gave off some great information! It was very interesting. Its crazy that the earth might have had life 4.1 BILLION years ago! I cant believe that there are minerals that were here for 400 million years ago.

  • danielm-jar
    10/28/2015 - 03:02 p.m.

    I'm surprised that this happened a long time ago. I wonder if aliens came to earth 4 billion years ago when humans weren't formed. I wonder how animals were made I wonder if it was the aliens who made us who we are. If the earth was like the sun and then the grass and plants were made how did living things be made or formed.

  • andrewh-jar
    10/28/2015 - 03:25 p.m.

    This article does a good job backing up it's theory's with facts. It makes perfect logical sense. This artical is very interesting to think about.The presence of water is important to factor in because no water no life.

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