
Mimicking an impact on Earth’s early atmosphere yields all 4 RNA bases - curtis
https://arstechnica.com/science/2017/04/mimicking-an-impact-on-earths-early-atmosphere-yields-all-4-rna-bases/
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mtdewcmu
The hypothesis that goes something like

RNA bases -> RNA -> proteins -> life

seems to sidestep the issue of metabolism, i.e. what did the first organism
eat? What was its energy source?

When I picture life arising from nothing, the most plausible scenario seems to
involve increasingly intricate chemical reactions that initially do absolutely
nothing other than create longer and longer staircases for energy to step
through through before dissipating and becoming useless. In other words, you
start with metabolism first, and then get structure later.

It seems plausible that the earliest proto-metabolisms didn't use RNA or
resemble modern life in any way. There might have been a succession of proto-
metabolisms before getting to anything we would recognize as life. They would
likely not have left any fossil record.

Does this make any sense to anybody?

~~~
pierrec
Sure, you could start with metabolism first, and then get structure later. But
you can narrow it down even further by saying this: you start with _self-
replication_ , and everything else comes after. Evolution stems from self-
replication. This is why RNA, of all the things we know, is the best candidate
for the origin of life. The smallest self-replicating RNA is relatively small
and simple, and can arise spontaneously and mark the beginning of evolution,
given the right environment. The separation of structure and metabolism
doesn't even exist yet.

The fact that a self-replicating RNA could have arisen given what we know of
primordial earth is _extremely convenient_. Something different and unknown
could have come first, but it would have to fit the bill of "can arise
spontaneously" and "can self-replicate and pass down incremental
modifications", which is very difficult to pull off. We also have good
certainty that LUCA (last universal common ancestor) featured RNA.

I will also try to answer: _what did the first organism eat?_ The concept of
food/energy source doesn't apply so well to the first self-replicating RNA.
The environment features constantly interacting bases, and the competition
between self-replicating RNAs stems from this. The distinction between
individual organisms and the environment isn't as clear-cut as what we know
now. Through this competition, one of the first things to be acquired was
probably a membrane. Eating can become possible and/or useful after you have a
membrane, which also allows you to extend the environment in which you can
thrive.

~~~
mtdewcmu
I went through several different ways to approach responding to your comment
before writing this version. I think this is most succinct.

Self-replication can itself be viewed as a metabolic process. You really can't
have replication before metabolism, because replication is metabolism. The
question is which metabolic process came first.

Since replication is anabolic and requires an energy source, it seems like it
makes sense to deal with energy first.

You can have reactions that harness energy to do nothing useful -> reactions
that harness energy to cause self-replication -> life.

~~~
pierrec
>I went through several different ways to approach responding to your comment
before writing this version.

I also edited it quite a bit (but now I'm done, promise...) One of my points
is that replication does not require a separate energy source, in the right
environment. RNA is highly reactive given the right temperature and
conditions, this is why all modern life does not use it as permanent storage
medium (this also makes it very difficult to work with in the lab). Only
replication of a DNA-based life form strictly requires a control mechanism and
energy source.

~~~
mtdewcmu
>> One of my points is that replication does not require a separate energy
source, in the right environment. RNA is highly reactive given the right
temperature and conditions,

I actually don't know what a flask full of RNA will do when left to its own
devices. My science education has gaps. However, really basic chemistry says
that you can't create big molecules from small molecules without some sort of
energy gradient, because​ the big molecules have less entropy than the small
ones.

When you have a flask full of stuff, what it does spontaneously is go to
thermodynamic equilibrium. If you want a self-sustaining reaction that creates
specific big molecules over and over, you need to keep adding energy.

~~~
TeMPOraL
Fortunately, Earth is located near a huge fusion reactor, and comes equipped
with its own auxiliary internal fission reactor. There was plenty of energy
gradients in the environment then, the same way there are now.

------
Blinks-
When I was in middle school I read a new book about cell structure I found in
the library, my favorite chapter was always about the so called primordial
soup of lipids and simple organic compounds that could have setup the chemical
basis for polymers to form and in turn create the building blocks for RNA. It
was one of the main things that gave me an interest in science and
engineering, up until that point people had always given me a "god did it" or
"we still have no theories on that son". This brings me back to the good ol'
days of trying to explain how RNA could come about, as a 12 year old, to
middle aged religious teachers who shot me down every time. As a kid this made
me turn to outside sources for knowledge, and in retrospect that was actually
a good thing.

~~~
jacquesm
12 to 15 is roughly the time when as a child you realize adults are just big
kids and are wrong as often as they're right. It's hard to get back to some
level of respect after that, it's a bit like finding out Santa does not exist.

~~~
Arizhel
I'm over 40 now. I realized what you're saying to an extent, but for a long
time I assumed that older adults would have the benefit of wisdom, life
experience, maturity, etc.

As I've aged, I've been consistently disappointed. I now believe differences
in how people behave, according to age, are really a product of generational
differences, and that people really don't change very much after they pass 30.

------
deepnet
67P Churyumov-Gerisimenko is a very dirty snowball.

Comets may have brought much of Earth's water.

Ice, dust & tholins.

Tholins are a sort of like a simple crude oil, thick tarry and orangy brown -
very rich in primitive organics and amino acid precursors.

Pluto is red with tholins.

[http://www.planetary.org/blogs/guest-blogs/2015/0722-what-
in...](http://www.planetary.org/blogs/guest-blogs/2015/0722-what-in-the-
worlds-are-tholins.html)

------
apo
This type of research is mostly a dead end. Abiotic processes for generating
amino acids and nucleotides from smaller components are well-known.

The mystery revolves around how these building blocks turn into life through
abiotic processes. We really haven't got a clue. As a chemist, I view this as
the most important unsolved problem the discipline has to offer.

Solving this mystery would likely be the most significant turning point in
human history.

This reminds me of something Paul Graham once said. Knowing a problem exists
isn't sufficient justification to solve it. You also need an approach. The
approach to solving the origin of life problem does not exist (yet).

~~~
gnaritas
> Solving this mystery would likely be the most significant turning point in
> human history.

I can't imagine how; most people will simply dismiss it and continue praying
to their Gods and scientists already believe what it would prove so few minds
would change and unless it directly leads to some practical output it simply
won't matter to most of the world.

~~~
apo
With understanding of a process comes the possibility (or inevitability) of
controlling it. I'm not referring to mythology, but rather technology.

~~~
gnaritas
Which is what I was referring to by some practical output; however it's
possible and common to acquire knowledge without there being immediate things
to do with it. Certainly the knowledge is progress, but you called it the most
significant in human history, that's a bold claim, care to expand on how so?

------
aristus
In the 1950s they discovered that sending high current through a (sterile)
organic watery soup would generate a dozen or so kinds of amino acids. The
hypothesis was that tens of millions of years of lightning strikes on the
ocean could in theory get the party started.

~~~
SomewhatLikely
That experiment is literally described in the first paragraph of TFA.

