Basically I’m aware of how Big Bang led to expansion of universe, gases, atoms etc. But how did some presumably basic radiation/heat mechanisms lead to literal organisms that had life? It doesn’t make sense to me.
In: Biology
Carbon naturally forms complex organic molecules. Sometimes these molecules are able to react with each other. It’s conceivable that a complex molecule could form that attracts simple molecules in a way that forces them to form together as a copy of itself.
You then have a situation where you have these large molecules competing with each other for resources to make more copies of themselves, and because they are relatively simple the copying process is error prone leading to lots of mutations.
Sounds familiar? We have everything we need for evolution to begin and evolve life as we know it.
No one really knows. A lot of the building stones, e.g. nucleic acids, hydrocarbons and amino acids are spontaneously created in abiotic environments from much simpler molecules in the presence of heat, uv-radiation and pressure.
The leap to a self-replicating entity is huge, however, and of infinitesimal low probability. But then again, the universe IS pretty big and did have a lot of time….
Think about the human brain. The brain is made up of a huge number of molecules arranged in a specific way. If you were to randomly shuffle those molecules 100 times, what’s the probability you’ll create a functioning human brain? Pretty much zero, or close to it. Now instead, consider a very very primitive single-celled life form. Essentially just a basic cell that is able to use energy around it and replicate itself. Compared to the brain, it is much more likely you could recreate this single cell by shuffling its atoms around, especially if you had a really really long time to do so.. The conditions we believe are necessary for life to evolve from dead matter involve high temperatures, pressures and lots of chemical reactions. Our leading theory is that at some point life began deep in the ocean near thermal vents. This is a place where lots of the right molecules are in the right place and they are constantly getting shuffled. Over a long enough period of time and stability, it just so happened that life appeared out of dead matter
There is a field of study called abiogenesis, which studies precisely this topic. In part scientists have some good ideas and have tested some elements of it successfully but the thing we can’t test is the millions of years and vast environmental factors spanning a planet to piece all the pieces together and show it happens.
Given enough time and chemical interactions with the dynamic forces (thermal vents, tidal mixing, volcanic eruptions) and minerals that we believe were present at the time it is conceivable that the simple chemical strands developed and scientists need to show that four (iirc) key components came about in environments that we have confidence existed at that time.
There is still a great deal of work to go in this field but there has been some successful experimentation showing some of the right reactions on a small scale.
The science does NOT say the creationist strawman of a bolt of lightning hitting some primordial ooze or mud or a rock. There is also a strawman of should be able to make life from a jar of peanut butter.
So why haven’t we unlocked this genesis code to create life?
What you are asking is an ongoing question. The study of this is called abiogenesis.
Now we admittedly have no definitive proof of how it happened. But we do have complex life, so it happened somehow!
We have established that in the conditions that would probably have been present in the early stages of the earth. It is possible for the chemical building blocks to be present, and combine to form amino acids, early proteins. This is the basic building block of life.
In 1952 a now famous experiment, the [Miller-Urey](https://www.youtube.com/watch?v=NNijmxsKGbc&ab_channel=StatedClearly), experiment established that it was possible. Later work repeated, and built on this. Making this not only possible, but given the huge periods of time involved, quite probable. Later experiments found that you can get to the amino acid stage from a surprisingly wide range of starting points.
WE have even found traces of amino acids and complex sugars out in space. So we know that it’s not just happening here on earth. In fact ti is more common that we have ever previously imagined. But given the wider range of conditions in the vast universe, and a 14 000 000 000 year time frame, perhaps we shouldn’t be so surprised.
You are asking a very deep fundamental question for which there is no ELI5. It’s a hard question to answer even without an ELI5 constraint.
But you can ask the same about a river: how did seemingly innocent H2O molecules lead to a river that seems “alive”? It flows, it changes path over time, it can even cease to exist. It is a very complex thing that exists because of many properties of matter and forces that somehow end up creating a river somewhere. Or you can ask the same about stars.
Life is kind of the same thing, an emergent property of otherwise simple carbon matter given its properties and the forces acting on it.
Richard Dawkin’s book The Selfish Gene does a good job of explaining how life began and started to evolve. Nobody knows how the very first self-replicating molecules came to be, but the book explains how once that happens, life as we know it is pretty much inevitable.
There were probably millions of times when crystals *almost* became autonomous self-replicating organisms … but it only had to happen once, and then we were off to the races.
Latest Answers