Our earth is really old.
Estimates put the age of our earth at 4.5 billion years.
For 1.5 billion years, it was desolate, no life existed.
But Somewhere around 3 billion years ago, life began to sprout on planet earth.
Scientists know this based on fossilized bacteria found in Greenland that are around 3.7 billion
years old.
But what exactly makes our planet so special, where ours is the only one that we know of
that allowed for life to form?
Today, life’s biggest questions asks, Where did life come from.
Hello and welcome back to life’s biggest questions.
I’m charlotte dobre.
Don’t forget to give us a thumbs up and subscribe and let us know in the comments
below what topics you would like to see next.
Up until about 100 years ago, there was only one possible explanation for the origin of
life on earth, god.
But since then, modern science has given us several theories on the origin of life on
earth.
At this time, there is no one theory that’s fully accepted among experts.
Many scientists believe the earths oceans were once covered in ice.
Remember, this was 3 billion years ago we are talking about.
Our sun was only about a 3rd as bright and powerful as it is now.
That means that our oceans were probably covered in a thick sheet of ice, hundreds of meters
thick.
At the same time, our atmostphere was still very young, which means that there was a lot
of radiation from the sun hitting the surface.
The thick layer of ice would have protected the organic molecules, allowing the key reactions
to happen later on.
Organic Chemist Alexander Graham Cairns Smith from the university of Glasgow suggested that
life could have begun through clay.
Clay contains mineral crystals, which could have arranged organic molecules into organized
patterns.
As time went on, the molecules started to organize themselves.
Then theres the idea that life began from a spark of electricity, specifically, lightning.
Back when our planet was still very young, its atmostphere was also very chaotic.
It was filled with volcanic clouds that could have consisted of methane, ammonia and hydrogen.
It is a possibility that lightning from these clouds struck the surface of the earth and
that got the ball rolling.
Amino acids and sugar can be generated from electricity.
We know this thanks to the Miller-Urey experiment in 1953, where Stanley miller and Harold urey
mimicked the primordial conditions on primitive earth by exposing specific gasses to an electrical
charge.
At the time, the scientists didn’t analyze the products of the hydrogen sulphide reaction.
Later on, a former student of miller discovered the old bottled samples, and found 23 and
other organic molecules within them.
Understanding how DNA formed is key to understanding how life formed.
The reason why the origin of life is so hard to determine, is that DNA needs protiens in
order to form.
But protiens actually need DNA in order to form.
Scientists don’t know how these two building blocks could have formed without the other.
Its kind of like the did the chicken come first or did the egg come first paradox.
But one explanation could be RNA.
RNA is similar to DNA but its more often found in nature as a single strand folded onto itself,
DNA is a double strand.
Many scientists believe RNA was a lot more prevalent when the earth was young and life
was primitive.
Cellular organisms as well as viruses use RNA to encode their genetic information.
RNA stores information like DNA, it can create both dna and protiens and it serves as an
enzume.
Later on, DNA, being more complex and much more efficient than RNA, began to develop.
But one thing that is uncertain is how RNA ended up on earth at all.
It either popped up spontanteously, which would mean life in the universe is incredibly
rare, or it got here another way.
And perhaps the most compelling theory of all is that life on earth was actually brought
here from somewhere else.
Like mars.
Mars gets hit by asteroids quite often, so much so that chunks of mars have made their
way to earth.
It is possible that organic microbes could have been brought to earth.
Which would technically mean that all life on earth is of maritan origin.
Another prevalent but controversial theory is that life came to earth by catching a ride
on a comet from elsewhere in the galaxy.
Maybe it was a combination of two or more of these theories.
We just don’t know, because we cant go back in time 3.5 million years.
How do you think life began on planet earth?
Let us know in the comments below.
For now, I’m charlotte dobre and you’ve been watching lifes biggest questions.
If you wanna go on an lbq binge, check out our playlist biggest what ifs.
And make sure notifications are turned on so you never miss a video.
See ya.