I'm fairly amenable to the interpretation that something like prokaryotic-to-eukaryotic jump is a real high barrier.
I would be pretty unsurprised to find prokaryotic life at least sometimes. I would be much more surprised to find eukaryotes possibly at all, and probably at any high frequency.
Doubt it. Cellular endosymbiosis has happened lots of times on Earth. Besides the common algae symbiosis, I once read a paper that contained a casual reference to dinoflagellate-based organnelles in a larger cell. And dinoflagellates are eukaryotes themselves!
Good find. I might have actually remembered the dinoflagellates on the wrong side of the endosymbiosis relationship in my example (this is either similar to our the same as the one I read). The broader point stands. :)
Why would you think that the prokaryotic-to-eukaryotic jump is higher?
If it is engulfment of organelles like mitochondria, that happens all the time. There are fairly good models of the evolutionary tree and how it could happen over time[1].
On the other hand, the ribosome is an amazingly complex machine, which I would expect would be much harder to create. Even synthetically, the path to build a synthetic eukaryote seems a lot easier than the path to build a synthetic ribosome.
It's not clear to me how much these features can be degraded without destroying the ability for organisms to reproduce with heritable traits.
Also, when listening to these videos, ask yourself 'how' and 'why' any time an action is described. For example, the following parenthetical questions from a small chunk of the 'Translation' video:
"The addition of each amino acid is a three-step cycle; (Why three step?)
First the tRNA enters the ribosome at the A-Site (Why does it only enter at the A-Site? How are other options prevented and/or made inconsequential? Was it always this way? How did the features of the A-Site evolve for this to happen. What happened before this? ), and is tested for a codon / anti-codon match with the mRNA. (How is the tRNA tested? What happens when it fails the test or is missing the amino acid? What is the energy budget of this test and what are the specific features of the ribosome, RNA, tRNA and amino acid that make it possible? What happened before this testing was done? How did we get from the lack of ability to test and the ability to test?)
Next, provided there is a correct match, the tRNA is shifted to the P-Site (What is the mechanism of this shifting? Why does it only go one direction? What is the energy budget of this process and how is it powered? How do we prevent multiple tRNA from shifting or keep it from shifting more than one spot? What occurred before the ribosome/RNA/tRNA/amino-acid had the features to allow this to occur?)"
The systems are very complex, but what I see is a few active sites and a bunch of random stuff that happens to hold them in the right spots to control them a bit.
When reasoning from first principals about immune response, it occured to me that just a few simple processes might be all that is required to explore novel active structures in an organism.
Based partly on my understanding of a study of bacteria that evolved the ability to metabolise a new nutrient, a mutation prior to use is required. The ability to detect a molecule might evolve based on immune responses that use random sequences as "test" active sites that are checked for a specific type of deformation.
If this random sequence deforms immediately, it is discarded because this sequence either deforms automatically or deforms in the presence of something common to "host".
If the test remains negative it is released from the host training environment. If the test pattern deforms some time later, it has detected a "foreign" molecule, and has the potential for use as part of a protein that manipulates this molecule.
Recovering the sequence that detects this new foreign molecule becomes the first step in a hereditary immunity. It also stores this useful sequence for possible use in other "testing" systems. These might bring 3 or 4 of these random test systems together to perform another test.
Simple systems that explore a complex space can come up with seemingly elegant solutions.
The most obvious answer to any of your questions is that, if it worked a different way, that's what the video would show... or there would be no video at all.
I wonder how often eukaryotes were created but then failed to outcompete the existing prokaryotes. Complexity often results in poorer algorithmical fit in the short term.
Indeed. It's probably the case for every step in the evolutionary ladder.
As for eukaryotes, often, evolution rewards larger size, simply because if you are larger you can't be eaten as easily, you can eat larger prey more easily, etc. Compared to prokaryotes, eukaryotes are gigantic. And they seem to cover the niche of huge lifeforms really well.
But would have that been the case for the first eukaryotes? The very first might have been a similar size to its predecessor, no?
I wonder how many early iterations of eukaryote might have actually been smaller, perhaps, if the organism required additional energy sources to support growth.
Eukaryotes have lots of ribosomes, so I'm confused about why it would be easier to create eukaryotes.
And while bigger cells absorbing smaller cells happens all the time, it seems extremely, extremely rare that those events lead to reproducing life. It's probably happened 2X on earth (whatever lead to the original eukaryotes, and the absorption by that lineage of cyanobacteria).
There are tons of insects with novel endosymbionts. For example, Camponotus ants have some novel endosymbionts - https://pubmed.ncbi.nlm.nih.gov/8866472/ . There are even synthetic endosymbionts nowadays (e coli in yeast), and there are cytoplasmic parasites like Wolbachia that you could imagine evolving into an endosymbionts.
On the other hand, even if had only occurred 2x, ribosomes occurred 1x - all ribosomes are related to each other and didn’t evolve separately.
Engulfing new creatures is a lot easier for large eukaryotic cells without a cell wall than it is for prokaryotes or archaea. We have a model of how it happened but there were a lot of problems that had to be overcome in the process, problems that didn't later have to be overcome for chloroplasts, etc.
My understanding is that metabolic-induced stress (degradation, esspecially genetic) was a major factor.
It's also possible that earlier similar transitions occured but were overwhelmed by the surviving eukaryotic line, whether due to greater metabolic effectiveness, superior repair capabilities, or other factors.
I would be pretty unsurprised to find prokaryotic life at least sometimes. I would be much more surprised to find eukaryotes possibly at all, and probably at any high frequency.