Life May Have Existed A Billion Years Earlier Than We Thought!

Hey everyone, Trace with you for a DNews Short We like to think we’re special, that life
only pops up once in a planet’s history.
But new research published in the Proceedings of the National Academy of Sciences says there
might have been complex life on Earth before us that eventually died off!
It might have developed in the oceans far earlier than we previously thought.
Looking for ancient life is hard because not everything gets preserved as a fossil.
In fact, according to the researchers, the probability of an organism becoming fossilized
is pretty low.
So instead of looking for direct evidence of life, they have to search for evidence
of the conditions to support life.
In this case, they looked for a form of the element selenium in sedimentary rocks over
2 billion years old.
Selenium reacts when it’s exposed to oxygen, so the researchers were trying to find evidence
of this oxidation.
This would be clear sign that there had been oxygen in the air at that time.
And they found it!
Based on the selenium traces they analyzed, the researchers were able to reasonably conclude
that oxygen was present in the Earth’s atmosphere between 2 and 2.4 billion years ago, which
is much earlier than our oldest recorded fossils of complex life; those are only about 1.75
billion years old.
Their research says that oxygen levels were possibly high enough to have an impact on
the planet’s ecology!
After this time period though, the oxygen levels crashed, and the life, if it had evolved,
likely died off.
So the next question is, what caused global oxygen levels to drop so dramatically?
There’s work to be done, but in the meantime, this type of research might help us look for
ancient life in extreme environments, like distant planets and moons!
And speaking of, what if life didn’t start on Earth but actually came from space?
We talk about that idea in this video.
What else would you like to know about fossils and the history of the planet?
Let us know down in the comments, make sure you subscribe so you get more DNews and thanks
for watching.

Life May Have Existed A Billion Years Earlier Than We Thought!

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