Every other Friday on Morning Edition, the Outside / In team answers a question from a listener about the natural world.
This week Bill from Lyme asks: “Does anyone know if the origin of life was a singular event, or was there a particular period in the development of the earth that spawned the creation of life in many places? Is there any evidence [that] maybe the process is still going on somewhere on or under the earth right now? “
The overriding question
In an 1871 letter to the English botanist Sir Joseph Dalton Hooker, Charles Darwin speculated on the origins of life on Earth, writing that it may have started “in a hot little pond with all kinds of ammonia and salts. phosphoric… ”
Fifty years later, a Soviet biochemist by the name of Alexander Oparin took up this idea and gave it a tastier twist: he called it the primordial “soup”.
So, yes, there was a period when scientists believed conditions on Earth were rich in the building blocks needed to trigger life. But has it caught fire more than once?
The oldest direct evidence of life are fossilized colonies of microbial organisms preserved in rock layers that date back 3.5 billion years. To have evolved to this point, the first organisms should have appeared hundreds of millions of years ago.
How and where exactly this happened is still a matter of debate, but it’s certainly possible that lightning struck more than once.
Stir the pot
You may be familiar with the ingredients of this primordial soup: things like protein, fat, and even RNA, the biological information storage system that is similar to DNA.
Even though these are things we associate with living organisms, these organic molecules can also exist outside of the living world. In fact, one of the ways they would have been added to the primordial soup was the impact of meteorites and asteroids on the planet’s surface during the “last heavy bombardment”.
Some scientists believe that the primordial soup that spawned life was brewed in deep underwater ocean vents, while others believe it was more likely to have been made in pools near hot springs and sunsets. geysers.
Regardless, these ingredients are needed to initiate some of life’s essential processes: metabolism (the conversion of energy into vital activities) and the ability to pass information from one generation to the next ( i.e. evolution).
Luke Steller prefers the geyser theory. He holds a doctorate. student and educator at the Australian Center for Astrobiology at the University of South Wales in Sydney, where he tries to recreate conditions similar to this primordial first soup. He likes the idea that it wasn’t a special moment.
“It’s a good chance [life] may have arisen more than once during this truly fertile period [when molecular building blocks were being delivered to Earth via meteorites]», Explains Luc.
But Luke also says it helps to think about it from another angle.
Imagine the most complete family tree, in which all living organisms on Earth – plants, animals, fungi, everything – branch out from the single trunk, when life on Earth first began. It is sometimes called the “tree of life”. The trunk, where all organisms eventually meet, is called LUCA – or “Last Universal Common Ancestor”.
“You can also imagine that this tree of life has an interconnected root system underneath,” says Luke. “So you would have had all these different chemical processes, RNA in one pool and metabolism in the other, coming together and eating each other… collaborating together and ultimately forming this LUCA bottleneck. then evolved from that bottleneck to everything else.
So, life (or its chemical building blocks) may have been triggered more than once, only to be eaten and end up in the same original organism from which all life as we now know it originates.
Now, to quickly answer Bill’s second question: Could this happen again today? Probably not.
The days of the primordial soup are largely over. The oxygen created by the Explosion of Life (which really went mad about 2.2 billion years ago) is destructive to some of these organic molecules needed to start the process. And, even if that were to start, good luck surviving in a world that is now full of hungry predators.
“There are no bubbling pools full of organic RNA and all that,” says Luke, “because a little bit of bacteria will come in and eat this stuff away.”
That being said, Bill was on to something: Luke mentioned the possibility of a “shadow biosphere” deep beneath the earth’s crust, where there could be different life forms unrelated to our own family tree.
Mole people? Lava worms? Probably not, but who knows! I guess it’s time for another Journey to the Center of the Earth sequel.
If you would like to submit a question to the Outside / In team, you can save it as a voice memo on your smartphone and send it to [email protected], OR call the hotline, 1-844-GO-OTTER .
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