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Cells are extremely complex self-replicating organisms. They are so small and yet they can pull off this trick of mitosis that no machine made by humans ever ac
by est31 7y ago
Cells are extremely complex self-replicating organisms. They are so small and yet they can pull off this trick of mitosis that no machine made by humans ever achieved. Personally I think that the most interesting and hardest part in the evolution of life was the start of it, where you go from random proteins to self replicating structures (cells).
It's easy to think of in-between steps for any post-cellular-life step in the evolutionary process that led to intelligent life but if you have no self-replication you can't have evolution. Most likely at the start proteins just floated around freely in water and did various random things, most of them not really useful. Every now and then some, by chance, some protein would do something useful. Now earth is big and before life, proteins could float around freely without being repurposed by bacteria or other organisms as building material.
But the best protein that's the result of random processes isn't helpful without the ability to clone it in some way. Proteinbiosynthesis [1] is an extremely complex process that involves multiple substeps each needing complex proteins of their own to facilitate it. It also needs an ample supply of ATP that has to come from somewhere and not be wasted by "useless" proteins.
The most simple cell that we can build today has 531 thousand basepairs [2].
[1]: https://en.wikipedia.org/wiki/Protein_biosynthesis https://en.wikipedia.org/wiki/Protein_biosynthesis
[2]: https://doi.org/10.1126/science.aad6253 https://doi.org/10.1126/science.aad6253
- Retric 7y agoSelf replicating protein are possibly something of an in between stage. https://www.sciencealert.com/amyloid-protein-self-replication-abiogenesis-contrasts-rna-world https://www.sciencealert.com/amyloid-protein-self-replicatio... Paper linked at the bottom: https://www.nature.com/articles/s41467-017-02742-3 https://www.nature.com/articles/s41467-017-02742-3
- pierrec 7y agoIt's unlikely that the first self-replicating organism at the origin of life was a protein. As you point out, there are just too many moving parts that need to come together simultaneously. These days, I believe research is tending towards something closer to RNA, which has the nice properties of both encoding information efficiently and catalyzing reactions involving its own nucleotides. It may also have started with a type of genetic polymer that no longer exists in life as we know it. Interesting but approachable article on the topic: https://www.newscientist.com/article/mg21128251-300-first-life-the-search-for-the-first-replicator/ https://www.newscientist.com/article/mg21128251-300-first-li...
- est31 7y agoThanks for the pointer!
- jonplackett 7y agoI read an interview the other day with a scientist who thinks life must have come from another planet based purely on how insanely complex even basic life is. He just said it happened much too quickly to have evolved here. Apologies, can’t find the original article.