Where did the first micro organisms on earth come from?


Whenever someone talks about the first stages of life on earth they always start when there are already organisms. Where did those first organisms come from?

In: 7

We don’t know. That’s really why people don’t talk about it. We have a pretty good idea of how life evolved from very primitive organisms, but we have no way to really tell where those first organisms came from.

We have a bunch of guesses. It is possible they came to Earth on a meteor that crashed onto the planet (although this doesn’t explain how the first organism *elsewhere* formed). It’s also possible that they formed out of a “primordial soup”. Imagine some prehistoric pond filled with water and ammonia and carbon and other stuff. Hit it with some ultraviolet light (which the sun can supply), and a bunch of simple amino acids and proteins and sugars will form. We’ve done this experiment in a lab and found that it actually produces most of the basic building blocks we’re made of.

And perhaps if you allow this process to continue over millions of years on an entire planet, eventually some of those will randomly combine into the first simple living cell.

But we can’t really tell. All we can say is “it might have happened in this way”.

We cant say 100% how it happened but we do know organic compounds form independently. And they interact, group together and “eat” each other. Over time chemicals interacting and doing what they do could have through some sort of proto evolutionary process led to something we could call life. Life wasnt created in a single event but through a process.

This subject is called abiogenesis.

There have been life on Earth for so long that continental shift have deleted any possible archeological evidence of the first life. And when we look at common things in all life it is quite a bit of things common which suggest that any alternative early lifeforms have gone extinct. So we do not know how life first formed. When we try replicating the early conditions on Earth, heat, lightning, carbon dioxide, nitrates, ammonia, etc. we do see some of the basic building blocks like amino acids, fats, nucleic acids and even some cell membrane looking things. But we have not been able to find the right combination to create actual replicating life, although with more time this should theoretically be possible.

One popular theory, although without much evidence to it, is called panspermia. The theory is that life evolved somewhere else first. We know Mars had more life friendly environment then Earth in the early solar system, maybe as much as a billion years before Earth. But life might have evolved on a planet in a different solar system or even a different galaxy. A big enough meteor impact on this planet could have thrown up a large chunk of rock with microorganisms on it and this rock could have eventually impacted Earth. The microorganisms might have survived this and started colonizing Earth. We are looking for evidence of this theory but so far there is little to suggest that life did not originate on Earth.

We don’t know for sure and probably never will, but we do know of a mechanism that could have done it, and we do know that it must have happened, so if it turns out that there are no other mechanisms, we can be pretty confident this is what did it. Unfortunately, explaining that mechanism is pretty difficult, but the basic idea is that there are certain types of organic molecules that can occur spontaneously (specifically, RNA, which is basically the precursor to DNA, and amino acids, which are the building block of proteins, the things that Do most of the Stuff in cells), and in certain arrangements, these can cause copies of each other to be produced. And that’s all a cell really is – RNA and proteins making copies of each other. The problem isn’t so much “how did this happen?” but more “This thing can happen, but how lucky did Earth get to be the place where it did?”

Some people say God is the only answer. You should only believe that if you are five though. The above responses are great.