First life form? Or just the one that survived?

[One Above All]

As you probably already know, all life on Earth most likely[1] came from one single original life form. However, given that evolution is basically survival of the fittest, wouldn't it be possible that there were other, older, life forms that simply didn't make it? It wouldn't have been very hard for them to die, given the conditions on our planet a few billion years ago. Or did we just "get it right" the first time?

1.	In the sense that it was probably one, but it might have been more.

[Quesi]

Lucifer-

You know A LOT more about science than I do, but I was watching a documentary a few weeks ago, which presented a theory that the first life forms on earth actually fed on methane, and that oxygen was toxic to them.  The documentary went to on present these organisms as the cause of a huge, drastic worldwide temperature change, that almost wiped out all life on earth.  The survivors of this worldwide crisis, according to this theory, were our most ancient ancestors. 

I don't remember the name of the documentary, but I did a little googling and found this article, (popular, not scholarly) on the theory. 

http://www.damninteresting.com/how-bacteria-nearly-destroyed-all-life/ 

This theory seems to suggest that we didn't "get it right" the first time, but that drastic mutations of the original lifeforms when on to create the rest of us.

I don't know enough about science to even have a strong opinion about whether this is credible or not. 

What are your thoughts?

[One Above All]

That's how I was taught. The first life forms were photosynthetic and eventually poisoned themselves with oxygen. Thankfully[1], some already had mutated and were able to use said oxygen, and so "only" 90% of all life forms were killed in the first mass-extinction event.

1.	Seriously. We were very lucky.

[Quesi]

Wow.  I'm old I guess.  Science moves so fast, and those of us who are not in the field are hopelessly behind on current theories. 

I was blown away by the documentary because it was very different from what I was taught.  I had always been presented with the theory of microbial life becoming increasingly complex, with, perhaps, an occasional setback here and there.  The idea that the first known life thrived in an environment that would be toxic to life as we understand it, and the idea that this first life exhaled oxygen, which was a toxin to those little swimmers,  and ultimately killed them off, and that a few mutated survivors that thrived on oxygen became the sources of all life on earth, is completely new to me!

[RNS]

I'd thoroughly recommend the following documentary, which about the first life forms and how they evolved into the multicellular organisms we find today.