We know living things come from other living things. But how did the VERY FIRST living thing get here? Did it just pop out of nowhere? Can scientists make new life from scratch? If we took all the ingredients for life and put them on another planet, would life start there too after a long, long time?
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To begin, we have no idea how life originated. We have several theories, many of which seem varying degrees of plausible.
Of course, many people on this planet believe that life was created by some form of a god. Personally I don’t agree with this view, but to each their own.
Science offers up a few other possible options. The most likely of which is what is known as “primordial soup” – basically a kind of sludge that may have formed on very very early earth (maybe even before it finished cooling from a molten state) that contained every kind of amino acid, the basic building blocks of life. Over time through chemistry these amino acids eventually came together to form the first archea, a life form similar to and a precursor to bacteria.
Another slightly less plausible solution (IMO) is something called panspermia. Yes, sperm is the root of that word. The concept is that early life formed somewhere else, and then caught a ride on a meteor to earth, “seeding” the planet with life.
No matter what, there is no definitive answer to your question. This happened at least 3 billion, more like 4 billion years ago. It’s going to take a long time before we can answer this question for certain, if ever, as basically none of those geological records still exist.
Spontaneous abiogenesis.
Even if you subscribe to the theory of panspermia that just moves the location and time of the very first organism.
At some point, somewhere, a chemical stew had just the right conditions to create something able to produce offspring capable of producing offspring.
We don’t know but consider a simple example of a chemical reaction. Reactions release energy. If reactions occur they can be perpetuated when surrounded by the right ingredients.
This process can produce solid masses that simply go through a repetitive process of chemical reactions.
At some point these reactions become standard and plentiful. Eventually these simple bodies of chemical reactions begin to touch each other and due to there similar chemical components they spark the same reaction and thus produce a copy of the bodies.
These bodies had to have had road blocks such as chemicals that dissolve them. After many iterations some bodies picked up other chemical defenses that counteracted this.
So now you have a mass that can replicate and defend itself without any conscious agency whatsoever. Now the process of life has been set in motion. The rich life we see today is due to the billions and billions of repetitions that became more and more complex over an indescribable amount of time.
The eli5 (non-religious) version of this starts with the fact that the simplest form of life is much simpler than you might think.
Even things like bacteria have had millions upon millions of years to grow in complexity from the origin point of life, which really requires only something that can a) copy itself, even if only imperfectly and b) stay together long enough to make that copy.
There are many theories of exactly how life might have started on earth – with simple RNA or DNA, for instance, or with other cell components — but the basic idea is that the chemical components of life were found in abundance bumping around and eventually combined in just the right waym.
Imagine a pool of water, filled with chemicals. One theory has it being a shallow pool, and another has it in the ocean depths near geothermal vents. Either way, you have chemicals floating around in water, mixing into a wide variety of compounds. Now imagine that a particular compound is created randomly. The compound is nothing on its own, but combined with the next part, it becomes important. Before that, it is just another random collection of atoms.
Separately, lipids in the water form little bubbles. Not much different than soap bubbles, really. Now imagine many of these random compounds getting caught in these little bubble packages. Any number of combinations do absolutely nothing, but a specific set of random compounds get caught in the bubble, and something incredible happens.
These compounds, when separated from their environment (so the water can’t dissolve them), but with a way to take in energy (through the thin lipid barrier of the bubble) become able to reliably produce energy. Resources from outside are absorbed, the compounds use the energy to create proteins, and waste product is able to be expelled from the cell (lipid bubble). It becomes a self-sustaining system.
Then, again through random chance, the chain of compounds that produce the energy become replicable (see RNA replication). You now have growth. After enough replication, the cell divides and you have two identical copies producing energy.
At this point, you have a cell that can take in resources, use the energy from that to produce proteins that then go on to create more complex processes, expel waste products, and replicate. This all happened by random chance, and there were likely millions of combinations that didn’t have this result. It only took one. Slight changes during replication create differences, and some of them become beneficial. The beneficial changes replicate more often, and it becomes a trait.
This series of events continues, and eventually you get something that can reasonably be called unicellular life. Taking in resources, producing energy, expelling waste products, and replicating are all key definitions of “life”.
Look up the Miller and Urey experiment that was earliest form of the Primordial Soup experiment. Their experiment was to see if the basic building blocks of life could be created from inorganic materials under conditions that mimicked Earth’s before life actually took hold.
Their experiment resulted in a number of amino acids being created, which are precursor requirements for any life.
Others have experimented with the setup but with slightly different starting chemical to see if similar amino acids would result, or new unknown ones being created (providing insight into the potential makeup of not-standard lifeforms).
The experiment was not conclusive, but it did re-enforce the idea of the Primordial Soup theory.
It probably developed from a non-living thing called a [self-replicating molecule](https://www.scientificamerican.com/article/life-rsquo-s-first-molecule-was-protein-not-rna-new-model-suggests/), a combination of atoms that causes chemical reactions which create more of the same type of molecule. DNA is an example of a self-replicating molecule, but the one that led to the original life form was probably something else; there’s lots of speculation and theorizing about what kind of molecule it was, as you can see in the article I linked above.
There are conjectures that life is actually an energetically favorable way to capture the flow and accumulation of high energy compounds. Keep in mind that before there was “life”, any molecules that were produced by chemical or photochemical or electrochemical processes in the early earth would remain for thousands or millions of years, just accumulating in a puddle or lagoon or deep inside rocks or on the surface of clay particles. There were no bacteria or mold or bugs to chew them up, only other chemicals to bump into and sometimes react. There was a constant stream of energy flowing in from the sun, lots of methane and water, no oxygen to speak of. Or so we think. And immense amounts of time and millions of square miles of rock and millions of cubic miles of atmosphere, heat from vulcanism and electrical storms.
It came from the energy field of another dimension. This life is just one little piece of a much more elaborate and complex reality. It’s a kaleidoscope of energy and layers too difficult to understand or explain. There is no first piece of energy or matter because time is an illusion. Perhaps we haven’t even invented it yet. And yes I’m rambling and have no idea what I’m on about right now bahaha.
Like many things, it’s a spectrum, not either-or. Life isn’t a magical property that things have or don’t. Are viruses alive, for example? Depends on your definition.
Chemical systems got more complex over time, from really simple to what we see today. Pointing at something and saying “That’s the First Living Thing^tm” would be arbitrary, simplistic and misleading.
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