Ancestral bug
Well, last week, I couldn't go for a long run. I had a very annoying flu, and I preferred to take care of myself.
So today I had quite a bit of rambling to do and that was it.
Since I started the race I asked myself: “Where do we come from?”.
It is notorious that I like to talk about evolution, so this question had to do with that. But I wasn't referring to where humans come from, something further back. Nor where do we primates come from, further back. Come on, not even our origins as tetrapods, or chordates, we don't even go as animals, much further back.
WHERE DO LIVING THINGS COME FROM?
It's complicated. Obviously, there is no fossil record of the last terrestrial common ancestor. In English, they call it LUCA, for "Last Universal Common Ancestor," but that term universal seems very presumptuous to me. I am sure that there must be other forms of life in the universe that have nothing in common with us, terrestrial living beings.
But let's return to the common terrestrial ancestor, the ancestral bug, as I said, there is no fossil record of that organism, we know that it existed since all terrestrial bugs have some characteristics in common, fundamentally that all living beings use ribonucleic acids, DNA and RNA, as genetic material, which, in addition, are right-handed as I mentioned in a previous post. Furthermore, they all have the same machinery for genetic translation (genetic code and ribosomes), which produces left-handed proteins. Not only that, all bugs have some genes that we share, which have the same function and sequence, which is why they have been maintained throughout evolutionary time. Some 355 genes have been identified with these characteristics, so at least that part of the ancestral bug's genome is known.
With this information and considering the conditions of the earth more than 3.5 billion years ago, what would the ancient bug be like?
Well, to begin with, it should not necessarily have been the only type of living being, of the common genes that living beings have, some have to do with a very simple immune system to defend itself against viruses, let's say a library of nucleic acid sequences that, if found, must be cut, known as CRISPR-Cas. So along with the ancestral bug there were other bugs, which, as I already discussed in other ramblings, were not alive, but were more alive than dead, and which, since then, were already causing trouble.
But what other characteristics? They were surely anaerobes, there was no oxygen back then. Most likely autotrophs, when they appeared there was no one to eat, so they had to produce their food, but they certainly did not use light. There are many processes by which energy can be obtained, without the need for light, using hydrogen, which was abundant in hydrothermal vents. At that time, geological activity was very intense, so these environments must have been much more common than today. Now, based on current autotrophic organisms, which do not use light, and live in hydrothermal pits, we can have an idea of some genes that are not universal but are very useful for those environments and those functions, so they must have had many more genes than those 355 common ones, some authors talk about a few thousand, like current bacteria.
So yes, having already had bugs to eat, some bugs must have begun to appear to eat them, the heterotrophs.
A question I ask myself, why did blue-green bacteria appear? They were the first autotrophs that used light, photosynthesizers, to fix CO.2?
It's a good question, to begin with they must have been far from the hydrothermal vents, since the conditions there do not allow for transparent waters. Well, that shows that life is like that, if there is some way to take advantage of something, and there is no competition, it will be taken advantage of.
And, thus, with food (autotrophic organisms) and predators (heterotrophs), the cat and mouse race begins, the Tom and Jerry game called I. With that, the competition and the need for specialization, which caused our ancestral bug to leave new forms of offspring.
We call those that are most similar to this ancient bug Archea, the other group that formed were bacteria, like the blue-green ones, which I already mentioned.
Later, some Archea began to “eat” some bacteria, but instead of digesting them, they took advantage of them. For example, they saved the ones that carried out photosynthesis to use; now we call them chloroplasts. Others that were very effective in transforming food into energy were also maintained, we call them mitochondria. This is how eukaryotes appeared, organisms with organelles, to which not only we belong, but all the multicellular bugs that exist.
So the ancestral bug, from which all terrestrial living beings come, was anaerobic, autotrophic and lived in hydrothermal suction cups.
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