how was the first living organism formed?
In: Biology
The real ELI5 is: “we don’t know” but that is of course not very satisfying, is it?
There are a couple of theories about it. I personally like the idea that the thermal vents on the sea floor played a crucial role in the process. These have everything a living organism needs: energy – both in heat and chemical, the actual chemicals needed to build a simple cell, and a porous substance which creates small chambers where simple self-replicating mechanisms may form spontaneously.
But the real answer is: we don’t know.
No one knows. Humans have proven with a few experiments that certain organic molecules can be created under conditions we believe existed far in the past, but that’s still nowhere near creating life.
One would assume that given enough time and opportunities these molecules would come together and form the first lifeforms, essentially out of blind luck.
We don’t know all the evidence would be so tiny and so long ago we have no direct evidence. The most viable theory is that amino acids and proteins could have formed on the early Earth, in the primordial soup it was possible for these building blocks of life to form creating the primordial soup from which life could have spawned. https://youtu.be/Kq3Os00pPJM
What we do know is that an early from of live called Cyanobacteria formed Stromatolites and in the process turned a Carbon Dioxide rich atmosphere into one made from predominately Nitrogen and Oxygen. https://youtu.be/ile60Q3zsMU
Another interesting hypothesis is that life on earth was seeded by asteroids or comets carrying microorganisms that formed elsewhere (maybe Mars, maybe outside the solar system). But this just pushes the question to how did these extraterrestrial microorganisms form. As others have already said, we currently don’t have a good understanding.
The best we can think up so far is a puddle had all the right chemical juices and maybe got hit by lightning
There’s growing knowledge that basic molecular precursors to things like RNA actually can form from cosmic processes and exist in large quantities in interstellar molecular clouds. When such a cloud then experiences local gravitational collapse and forms a new star and planetary system, that system is seeded with an abundance of these key precursor molecules. What happens next is not understood, but the general theory is that you need a bunch of stable heat sources in a suitable solvent for millions of years for abiogenesis to occur. On Earth, the most likely known candidate for that is geothermal vents in the ocean. Liquid water is arguably the best solvent for the kinds of chemical reactions needed to assemble organic matter.
There’s also a much bolder theory floating around that simple life may have first evolved shortly after the Big Bang. There was a period where the entire universe was filled with a bright orange glow and the general temperature was about 70 degrees F in space. That may have only lasted for a few 10s of millions of years, but with the entire universe in that state it could’ve created ample opportunity for basic microorganisms or their precursors to evolve in a space environment extremely different from what exists today. However, as far as I know there’s no known evidence of this. It’s just an outlandish but compelling concept that’s come up recently.
We don’t know. We may never know the exact method that happened. There are a couple of leading hypotheses, and the [Miller-Urey](https://youtu.be/NNijmxsKGbc?si=0OU4I3RyBaC4lkri) experiments give a good potential insight. It’s important to remember that the first life wasn’t a ‘click’ and then there was life. It took billions of years of simple cells. Search abiogenesis on YouTube, there’s a lot of videos on there.
There is no evidence for any satisfactory explanation. Hence it’s not known yet.
There are two popular assertions.
First, it is asserted that billions of years ago somewhere in the ocean necessary molecules came together. There is not enough evidence to turn this assertion into a theory.
Second, it is asserted that a piece of material carrying the first organism fell to the earth from space. There is not enough evidence to turn this assertion into a theory.
There are also other less popular assertions.
These assertions may be categorized as hypotheses. However, since there is not enough experimental evidence, calling them “scientific theory” would be incorrect.
I think the important thing to understand with this is that while we don’t know, the amount of time it took this to happen is difficult to full appreciate and comprehend. Scientists believe the big bang happened about 14 billion years ago. The first, most basic life forms are believed to have appeared 4 billion years ago. That’s roughly ten billion years of chemical and environmental dice rolls to finally land on whatever magic combination was necessary for life.
10 billion years is an insanely long timeline for random things to happen that are otherwise completely unexplainable.
Depending on how you define living. The first things to require outside sources of food, and reproduce happened by chance and good luck. Water is a great mixer, and with all the chemicals from the soil and air mixing together in the water, eventually a random combination turned out to be instructions on how to be living.
After a long time, random chance happened again when one living thing ate another, but instead of processing it for its own food, they formed a relationship to work better. The one who eats, and the one who turns that into energy. That turned into what we would call a cell.
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