Imagine you have a soup filled with lots of different chemicals.
You leave it for a *very* long time.
Some of the chemicals combine together in a shape that makes it easier for other chemicals to combine in the same shape.
You leave it for a *very* long time.
Some of the shape-y chemicals stick to another chemical that makes it *even easier* for other chemicals to combine in the same shape.
You leave it for a *very* long time.
The last step keeps happening in different ways, each time the resulting mix gets better at making more of itself.
You leave it for a *very* long time.
You have something approaching primitive life.
Edit: We’ve done experiments that involve sealing a soup in a container and doing things like warming it and passing electricity through it that hint at the very first stages of the above process, but to do the whole thing takes a *very* long time and we don’t have a good way of simulating time passing very quickly to do that.
We’re doing other experiments that involve cutting existing life into tiny bits and reassembling those bits to make something that does what we want, this is an ongoing area of research.
Abiogenesis is an extremely complex field that can’t possibly be explained to a five year old, but here’s the ELI15:
In the early Earth, there were several natural molecules that are very very simple. Things like CO2, H2O, NH3, CH4, and similar. If you have a collection of these molecules in gas form and you apply energy (such as through a lightning strike), they undergo chemical reactions that change them. Some of these byproducts are what we call biomolecules, molecules that are considered essential for life. Some examples include amino acids (the building blocks of proteins), lipids (fats), and nucleotides (the building blocks of genetic information). If you chain these molecules together in a certain way, you get the very first proto-cell, the very first life form.
To answer your second question, in the early 2000s scientists were able to recreate the polio virus in a lab from its constituent parts https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1490301/.
Viruses occupy a space that straddles the line between life and non-life to they’re a good candidate for something like this.
Life was essentially created out of chemicals bonding together in specific ways, through random chance and the addition of the right amounts of energy like heat and motion.
It’s very, very, very, very difficult to make this work. Almost impossible, the chances of us doing it are like 0.000000000000001% or something crazy. No human could ever hope to achieve it in our lifetimes.
But then, the Earth is so very old. If you have billions of puddles, streams, lakes, seas and rivers, over a billion years, eventually some of these random chances occur, and then more things happen involving the newer comibned chemicals and elements, because they’ve changed, so they may react to new situations every so slightly differently.
It would be like saying ‘one day a meteorite will fall through basketball hoop.’ It probably could happen, as meteorites are rare, and the chances of one going through a hoop is really slim.
But then, if you covered 2/3rds of the Earth in basketball hoops and left them for a billion years… eventually one would probably go through the hoop.
Same applies with life.
Life isn’t a thing that you can have, living things are just a bunch of normal things that have certain traits we associate with life: autonomous movement, decision making, refueling itself (eating), reproduction.
Non living stuff mixed in the seas for a long time, until it mixed into something we would consider to be alive. The ability to reproduce is really key here, because without it we would again have to wait for another living thing to form. But since the first living thing could reproduce, it would create copies of itself, making sure life wouldn’t end.
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