[ethbro]

I was under the impression that RNA replication was simpler and therefore likely to be the predecessor of DNA-copying organisms.

As for how: chance.

Given a bubbling stew of organic compounds with chemical energy gradients available, eventually a random reaction created something with the ability to self-replication.

Almost irrelevant of how simple / ineffective / unreliable that method was, it represented a huge advantage (in the numerical offspring sense) over sheer random reactions. This life therefore dominated and exploited the available energy to reproduce.

Then mutation begat mutation, as selection picked favorable traits and more and more complex systems of encoding and reproducing traits developed.

I'm not saying it's been proven (to my knowledge), but it seems reasonable given what we know. And moreover I don't see any "the beginning must have been fundamentally different than business as usual" requirement for whatever happened. As Ian Malcolm says, "Life finds a way."

[ricksharp]

What do you think of the point made in this video about the mathematical improbability of making a single protein by chance?

https://youtu.be/W1_KEVaCyaA

I've always heard people just assume it would happen given enough time, but I haven't seen anybody actually calculate the probabilities and deal with the real numbers.

Also, beyond the video, the simplest bacteria we have been able to discover/modify requires around 200 different types of proteins to function (numbering in the 100,000s all together in their specific arrangement inside a cell membrane.)

This is the minimal viable life form we know, yet just to randomly construct a single protein from amino acids would take a practically infinite amount of time given all the resources of the known universe.

Then 100,000s of those proteins have to randomly find themselves inside a cell membrane...

People are quick to dismiss complexity philosophically, but it just avoids the reality of it.

The numbers are so far beyond astronomical they make astronomical numbers look like basic arithmetic.

Anyway, I was hoping you could provide some feedback on whether you think the math is accurate and why it should or should not be considered.

[yequalsx]

Flip a coin 100,000 times. Make a list of the results. Now go to someone and say, "what's the probability of me ever flipping this sequence?" It's quite close to zero. But you did flip it. Calculating probabilities for things that have happened by asking what's the probability of it ever occurring again can be misleading.

[ricksharp]

Good point.

So this would only apply when a specific sequence is required.

In analogy, if making a puzzle the first piece could be cut randomly. However, the following pieces would have to fit with the proceeding pieces. And each additional piece would grow in specification.

So for a cell, it is true that there could potentially be a large number of proteins that could prove useful. However when that one protein requires 99 other protein types that "fit" with it in the puzzle of a single cell, then you have a specific sequence required which would be more and more precise for each additional protein.

In addition, since there is a need for 1,000s of copies of each protein type, there is also a need for factory proteins of even greater complexity.

In the case of every life form on earth, they all have these protein factories built-in which read the rna to create specific proteins.

Although, there might potentially exist other possible protein combinations that could create an alternative functional protein factory, any protein factory would have many interacting parts that each require increased specification as each part is included in the design.

In addition, it would be hard for a protein factory to function without a healthy cell holding all the necessary parts close together.

---

Another analogy would be like sodoku.

With a blank board, it Is possible to put any number anywhere.

However, as the game gets closer to completion, it requires a specific answer for each square.

If randomly putting a single digit in each square, the likelihood of getting a correct solution would be:

- 9^27 ~ 6e25 (possible random configurations of 1-9 in each square)

Divided by

- ~ 6e21 Number of correct solutions

So it would be like this for a random single cell:

- Number of possible amino acid combinations for ~100,000 proteins of average length ~50.

Divided by

- Number of protein combinations that would function as a living cell