so in the begining there were gases and stuff like hydrogn. overtime cuz of gravity they came together and made new stuff like oxygen. but all these were non living gases so how did things like FUBA or Ameba come from
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This is one of the big unanswered questions. Scientists are still researching it but getting an answer is going to be extremely difficult.
The tricky part of this question is defining what counts as life. Ultimately life is a process, it’s a collection of chemical reactions so life would occur when those reactions could happen. Which reactions happen under which circumstances is complicated.
But let’s say a living thing has two aims, to maintain itself and to copy itself. Then we can look at the points at which self replicating molecules were first stored in containers that protected them.
Thanks to chemistry we can see some molecules spontaneously arrange into spheres. For example if a molecule has an end that’s attracted to water and an end that’s repelled by water those molecules can group together with their hydrophobic ends at the centre of a sphere and their hydrophilic ends on the outside. Now you have a ball that can keep its insides in and its outsides out.
This ball is the perfect place for a self replicating molecule to self replicate without worrying about conditions changing too much.
So for starters let’s go back in time, around 3.8 billion years ago. Keep in mind what I am about to say hasn’t been experimentally proven but we will get to that soon enough.
At the 3.8 bya mark, things were weird. Earth wasn’t the beautiful paradise we live in. It had:
1. tiny bits of oxygen, O2
[the stuff we breathe]
2. Whole lot of Carbon dioxide, CO2
[the stuff plants use to photosythesise]
3. Whole lot of Nitrogen, N2
[The stuff that’s most of our present-day air content]
4. Little bits of–
Hydrogen (H2)
Hydrogen sulphide (H2S)
[that rotten egg smell]
Carbon Monoxide(CO)
[Incomplete burning of stuff like coal can release these, extremely deadly]
Now these are the basic gases that were there.
Now there was of course a hell lot of sunlight and lightning. (Energy sources)
So we have the gases and a source of energy!!
These combined and created organic molecules!! This is a huge deal as till here it’s been proven experimentally by Stanley Miller.
The next part comes in making these molecules grow and grow a hell lot. So here’s the tricky part. We need these molecules to combine and be macromolecules which is fine and dandy.
But they have to replicate themselves!
There is nucleic acid (stuff like your DNA) which does replicate on its own with a template strand (it’s like one strand of your DNA just makes a photocopy of itself)
But at that time DNA wasn’t the first nucleic acid. It was in reality RNA!
So now we have an unstable mutating nucleic acid that just desperately wants to divide and replicate.
So what is hypothesised is that it probably got wrapped in a phospholipid membrane and created a CELL.
(Imagine a filling wrap, where the filling is an RNA and it gets wrapped by Phospholipid)
What’s a phospholipid? It’s what makes up our cell membrane! It looks like a mutated sperm with a head (phosphate) and 2 tails (2 fatty acids)
RNA is like the ancestor of DNA in a sense. This RNA could replicate a ton and mutate a lot too cause it was way too reactive.
The reason why we have DNA for modern species is because it is a hell lot more stable and not unstable like RNA.
Cells divide because of the RNA. Metabolism arises.
What is metabolism? It’s like your food breaking down to give you strength!
Now remember that RNA is hella mutative and mutates rapidly.
Some work out for the cell to survive, and some don’t.
This trial and error keeps happening.
Slowly…like really really slowly they shift into prokaryotes.
What are prokaryotes? Simply put they are the older versions of our cells, with every organ in them just floating around without any membrane or anything in the cell.
Now some prokaryotes like photosynthesis! Like our nowadays plants they can make food too!!
The nucleic acid keeps mutating more and more.
Then we reach something like amoeba and stuff that you mentioned in the question.
Evolution happens, and organisms keep getting created! Complexity and body design become way more difficult to adapt to the harsh and ever-changing environment.
And hence life as we know today is formed.
To be noted that to date no cell has been created by recreating the early earth atmosphere.
I know it’s oversimplified and I skipped a lot of nuances but anyone please be free to add on and say where I might have gone wrong.
Firstly *we don’t know for sure* but there are some plausible steps for which we have varied levels of research.
It might also be worth bearing in mind that nonlife/life is a somewhat vague and arbitrary human designation and that living things are created from non-living all the time now though in ways that couldn’t happen back then.
But basically the organic compound building blocks of life are common in the universe , useful chemical reactions commonplace where there is energy and if you put these together you get more complex ingredients for something like RNA. At the same time we have fats that can naturally form ‘bubbles’ that can encase these things and begin to form the first proto cells and allow certain types of transmission across the barriers.
Purely as just a matter of interest I remember Prof Brian Cox saying that it seems like very basic cells happened relatively quickly once the conditions on Earth had calmed down a bit … it was the event of one ‘eating’ another and both surviving that then created the sort of complex cells we have now that took a long time.
A wilder question is “when did life gain consciousness”.
Is life really that different from non-life? It’s a collection of processes. What makes it different is consciousness and the ability to have experiences from a point of view.
To get a better idea of how life began you need to familiarize yourself with amino acids and proteins. These are the building blocks of life. Even things that technically aren’t “alive” (although that’s up for debate) like virus are composed of amino acids and proteins.
I think it will make it easier to understand if instead of going from gasses to humans, you focus on the sequence of events more, down to the point where amino acids become proteins. We know how amino acids form. We know how proteins create life. What we don’t know is how exactly the first proteins formed from amino acids.
Once life begins its pretty straightforward to understand natural selection. Before life begins its just chemistry. Its that very brief, nebulous point between the two time periods we don’t understand.
So i would like to first clarify some stuff about the origin of various elements.
At the beginning of the universe, yes it was all hydrogen. As stars fuse matter together over their lifetimes, a variety of elements are created up to iron, and in the resulting deaths of stars, elements beyond iron are created and expelled into space.
the molecules that make up organic lifeforms are primarily a mix of carbon, hydrogen, and oxygen, elements that are found quite commonly out in space, and even found bonded together on their own without life(Tholins are a good example of this).
The origin of life is unclear, but one of the more common theories is that near hydrothermal vents, where there is a lot of minerals, molecules made up of the aforementioned elements, and heat, and the right circumstances created the first sets of primitive DNA or RNA, which naturally wants to self-replicate.
Life is a special kind of pattern that can use energy to copy itself and act when things change around them. Lets look at another self copying pattern, fire.
Fire is when really hot stuff burns with the air and makes it even more hot. Most fire is burnable stuff like wood or plastic getting hot and combining with air to turn some of the burnable stuff into really hot air and ash. It is a pattern of change. This pattern can spread, as long as there is energy available in the form of burnable stuff. A bunch of piles of wood are sitting around, dead, but if you release fire into one part it can spread around to all of the wood and consume it. The fire copies itself and makes more fire out of the burnable things. It even breaths air and makes waste like living things do.
Everyone is taught what a fire needs: energy in fuel, air, heat. If it has those things, fire can exist and spread. Those are the basic rules for fire to be “alive” and spread. Life is similar, it has basic needs and if they are met it can spread. Life is a lot more complicated than fire, but it has similar basic needs: energy in fuel, air, water, nutrients. Instead of using heat to copy ourselves like fire, we use nutrients and water to build cells.
Most agree that a cell is the most basic piece of life, and it is made up of stuff like organelles and other small machines that we don’t consider life because they cant make more of themselves on their own. A cell has all the machines in it to eat fuel and air, release the energy, fix itself, and make more cells. Cells are made of lots of proteins, which are chains of molecules that fold themselves up into useful shapes. Proteins are like Lego, they can be assembled into little nano-robots that can move around, carry things, make and break things. Cells are partially made of proteins and can make proteins.
Proteins are considered dead because they don’t make more of themselves, they are more like a wrench or a vacuum cleaner that our cells use to get stuff done. But imagine if you had a big pile of tools as big as a house and they were all mixed up and could stick together, you may get lucky and end up with an assembly of tools that does something useful. It is harder to imagine an actual hammer and TV being thrown together to make something better, but for proteins the rules are different and this happens sometimes. If it happens enough and some other things go right, you could get a very basic cell.
I like Feisty-Permission-21’s response.
Simply put we don’t KNOW. We know that something happened right the beginning of something called the cambriun explosion which is called such because things went from very quiet, static and suddenly life in so many forms detonated across the planet “all at once” (it really took millions of years but that’s fast).
That sudden massive expansion of life in so many forms has never been explainable to anyone’s satisfaction.
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