[litespeed (OP)]

If the conditions for life were plentiful at the beginning, I would expect more then one line of evolutionary descent. After all, microbes of various types co-exist within the DNA set we observe today. I see no reason that separate lines could not also have coexisted.

[Jessica H]

DNA seems to only evolved once, as all organisms share the same "code" I don't think conditions were really ideal, just over millions of years there was time for things to happen.

[norcalclimber]

The thing is, we're not even sure how life managed to form to begin with.  The atmosphere of early Earth was such that neither DNA nor RNA could have formed(to the best of my knowledge), so we are trying to create a precursor in the laboratory.  However life on Earth happened, it seems to be almost immediately from a geologic perspective...Earth and Moon form 4.5 billions years ago...if life occurred by abiogenesis it would have had to show up 4.4 billion years ago because it seems to have covered the Earth with photosynthesizing organisms by 3.8 billion years ago.  All this while the Earth is getting bombarded by meteors, lol, almost makes you wonder if aliens terraformed the planet  []

[LeeE]

if life occurred by abiogenesis it would have had to show up 4.4 billion years ago because it seems to have covered the Earth with photosynthesizing organisms by 3.8 billion years ago.

Please explain the reason why it would have taken 6 billion years to occur and could not have occurred sooner.

[norcalclimber]

if life occurred by abiogenesis it would have had to show up 4.4 billion years ago because it seems to have covered the Earth with photosynthesizing organisms by 3.8 billion years ago.

Please explain the reason why it would have taken 6 billion years to occur and could not have occurred sooner.

I'm not sure if I quite follow your question?  Do you mean to ask why it could not have shown up earlier in the universe?  I don't see why it could not have, but that is a ~9 billion year time span...where do you get 6 billion from?

[LeeE]

4.4 billion years ago - 3.8 billion years ago = 6 billion years.

What you said is that if photosynthesising organisms existed on Earth 3.8 billion years ago then if life on Earth occurred via abiogenesis then that must have occurred 4.4 billion years ago i.e. 6 billion years previously.

Why must there have been a minimum interval of 6 billion years between the advent of abiogenisis and photosynthesising life?

[norcalclimber]

4.4 billion years ago - 3.8 billion years ago = 6 billion years.

What you said is that if photosynthesising organisms existed on Earth 3.8 billion years ago then if life on Earth occurred via abiogenesis then that must have occurred 4.4 billion years ago i.e. 6 billion years previously.

Why must there have been a minimum interval of 6 billion years between the advent of abiogenisis and photosynthesising life?

4.4 billion - 3.8 billion = .6 billion or 600 million years.

It's not me that says it needed to happen 4.4 billion years ago, it is the scientists involved.  They say that in order for Earth to be covered by semi-advanced life 3.8 billion years ago, the simplest form of life needed to show up 4.4 billion years ago.  I'm not sure why they are convinced it must have shown up then, you would have to ask them.

[LeeE]

Oops! - my bad maths.