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 from western Australia's Jack Hills and 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" or 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, 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, 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, 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. 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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Why does the presence of water factor into scientists thinking about life on earth?
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COMMENTS (36)
  • billiem-1-bar
    10/27/2015 - 05:07 p.m.

    scientists used to think that water was necessary for life to exist but now they found carbon fossils that date earlier than what they thought. I thought this was interesting because its amazing how smart people can be.

  • avab-4-bar
    10/27/2015 - 07:12 p.m.

    The factor of the water was brought up into scientists thinking about life on Earth because without water there would be no Life, everything needs water to survive, therefor without water there was no life before Humans and the distinct Dinosaurs.

    I found this article interesting because I have always wanted to know what Earth was like before Humans came in and destroyed its beautiful nature and spirit. I would like to know more about the physical geography of Earths surface before life and before water. Where there any trees? Where there any mountains? This article surprised me because what I knew and was told that before life Earth was a flat, plane and boring/ mysterious place.

  • jacksonm-2-bar
    10/27/2015 - 07:36 p.m.

    The chemo fossil was the first fossil ever found by paleontologists. 4,200,000,000 years must given some erosion to the fossil or even destroyed it but the different cord weights kept it a fossil that was still in tact.

  • Brandon1231-YYCA
    10/27/2015 - 09:15 p.m.

    People are now thinking about how life would be in 4 billion years. Well, actually, they said that the sun will explode in 4 billion years so that is how our planet will look like if that happens. I think that having these people think about something that will happen when they die. I think that when they do this they are just going to stress themselves out. They will think that they don't need to live anymore and they need to die. I think that they just need to stop doing this so that they will be able to concentrate on that things that are more important than these things and just be able to live a life that will make them happy.

  • lucasl-3-bar
    10/28/2015 - 06:43 p.m.

    Scientists factor in water to determine life on Earth because all known living things depend on water for even the most basic actions, such as respiration or photosynthesis. As stated by the article, scientists found carbon residue in a chemo-fossil similar to that of today's organisms. Similar organisms require similar factors, so it is likely that they could not live without water. Thus, water is a crucial factor to the possibility of life.
    The article was very intriguing because it was about a topic that I am very interested in, and showed the unique ways scientists use to search for life and understand Earth's history.

  • seans-2-bar
    10/28/2015 - 09:01 p.m.

    The presence of water factors into what scientists think about life because most life needs water to survive. This is shown in the recent water on Mars discovery because alien life has a much better chance to survive if there is water. This article was an interesting discovery about early life that I find informational.

  • noahf-3-bar
    10/29/2015 - 12:23 a.m.

    The presence of water factors into scientists thinking about life on earth because all life we know about needs water to live and without water there would be no life on earth.

    One thing i found interesting from this article is that in the article they say is "the Earth by 4.1, 4.2 billion years ago was basically behaving like it is today." I find this interesting because I didn't know the earth behaved like it is now, 4.2 billion years ago.

  • kieranw-3-bar
    10/29/2015 - 12:41 a.m.

    Scientists know that all organisms need water to survive, so Earth not having much water lowers the idea of organisms existing on earth before 4.5 billion years ago. Harrison's finding is phenomenal and gives scientists hope that Earth is older then it is believed to be. The zircon found in Australia truly shows how Earth has been livable and able to be occupied by humans for 300 million more years then scientists thought before the discovery of the zircon.

  • carsonk-2-bar
    10/29/2015 - 05:02 p.m.

    The presence of water factors into scientists thinking about life on earth because water helps living things function and without it on earth, then there couldn't have been lots of organisms."The belief has been that there was not enough liquid water for life to take hold this early." This article was very interesting because it is cool to know what out planet was life 4 billion years ago. This article surprised me because I thought that there probably was life that long ago.

  • vincents-1-bar
    10/29/2015 - 10:18 p.m.

    The factor of the water was brought up into scientists thinking about life on Earth because without water there would be no Life, everything needs water to survive, therefor without water there was no life before Humans and the distinct Dinosaurs. I found this article interesting because I have always wanted to know what Earth was like before Humans came in and destroyed its beautiful nature and spirit. I would like to know more about the physical geography of Earths surface before life and before water. Where there any trees? Where there any mountains? This article surprised me because what I knew and was told that before life Earth was a flat, plane and boring/ mysterious place.

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