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, when 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 gives them reason to theorize that life itself is more plentiful throughout the universe because it seemed to start up so quickly.
 
Researchers examined tiny grains of the mineral zircon from western Australia's Jack Hills and 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" or a certain mix of carbon isotopes, 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, 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, which is what scientists usually find in remnants of life, 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 and 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, 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, who also wasn't part of the study, said Harrison's findings make sense and the accelerated timeline of life fits with his 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 (29)
  • benjaminc-day
    10/27/2015 - 01:09 p.m.

    Scientists seemed to have found what life might have looked like 4.1 billion years ago. This is a big breakthrough because it could mean that if life formed so quickly on earth, than it could be on other planets and other places in the universe. Forever we have wondered whether other life was on other planets and in the universe in general and if we can understand more about the origins of earth, we might know more about the universe. I think there has to be life somewhere in the universe that we don't know about. It is too big and there has to be other planets like earth that are capable of supporting life. It would be interesting to see how evolved the life on another planet is compared to earth. If these studies are any indication, life on another planet could have evolved similarly to us depending on age and its conditions.

  • ShawnaWeiser-Ste
    10/27/2015 - 03:41 p.m.

    When I was a child, I also believed that the earth was only the same age as me. 5 years to about 4 billion years is a phenomenal number of years. It just goes to show how oblivious the normal citizen is.

  • bradleys-jen
    10/28/2015 - 02:01 p.m.

    This story is very interesting and I personally think that there could have been life 4.1-4.2 billion years ago. This could also start theories about other life-forms billions of years ago. But I still believe that there might have been life a few billion years ago.

    • rodriguez-menaj-rob
      10/28/2015 - 02:54 p.m.

      personally i believe of other life forms not discovered yet by sciantists and fossil finders(I dont know the exact name for it) like one thing i learned is that many miles of land from millions of years ago is currently underwater so i believe if a search is made on underwater loacations i think we may find some fossils or some hints to currently unknown life species. but then again thats just a theory,a science and history theory

  • holdeno-3-bar
    10/28/2015 - 05:16 p.m.

    Water factors into life on Earth because all life needs water to survive. The author mentions that there is evidence of life on Earth 4.1 billion years ago, before water was thought to have been in existence. (paragraph 7) Scientists have determined that all present life forms need water. This new evidence shows life before water should have formed. This means that either: a) Water had formed 300 million years earlier than thought, or b) life 4.1 billion years ago survived without water. This selection of interesting ideas would factor into thoughts about life.
    I liked this article because it sheds light onto the origins of life on Earth.

  • tylerf-pla
    10/29/2015 - 12:12 a.m.

    Overall, this article says that carbon residue found in minerals hints towards life being on earth a lot sooner (300 million years) than predicted. This is not concrete evidence though because there are some unusual cases that this specific carbon residue does not come from life. Although, say the carbon residue is from life, that would mean that Earth couldn't have been the molten form we thought it to be for life to be on it. Earth must have been like it is now, 4.1 billion years ago. The main reason this article relates to me is because I always have had a large interest in space, planets, stars, galaxies, etc. and anything of that sort intrigues me.

  • pasham-jac
    10/30/2015 - 12:38 p.m.

    interesting

  • tylerh1-lam
    11/02/2015 - 09:41 a.m.

    Personally I think that there are still many thing to be discovered on earth scientists and explorers have still not even discovered part of the ocean and I think that there still are other life forms out there.

  • jakes-lam
    11/02/2015 - 09:47 a.m.

    This arcticle shows a lot about how little we know about Earth's past, this also shows that there could be other life that we are yet to discover that lived billions of years ago.

  • lydiab-lam
    11/02/2015 - 11:41 a.m.

    Crazy how small 400 million years can seem when it's compared to 4.5 billion years.

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