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Memories of the 28th Century

Maybe We Are Alone

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I ran across another article about the probability of finding other intelligent life forms in the universe. Alas, it is behind a pay wall, and I do not wish to sign up for something else. But the abstract does not mention mitochondria nor does the article from which I learned of it, so I would guess that it did not consider how difficult it might be for a single cell lifeforms to take mitochondria, or some similar bacteria, and make it symbiotic.

I think that the ideas about how many planets have intelligent life probably are right, it the symbiotic use of mitochondria or similar bacteria is common. My thought is that it may be rare for prokaryotes to absorb something like mitochondria and become symbiotic with them, because they usually would eat them.

The probability of symbiosis is incalculable, because we only know of it happening once, and there is a probability that it only happened once, but we do not know for sure. I believe that the uniqueness of the symbiotic situation makes many religious people confident in their belief that the Gods created Earth as a special place and created humans to enjoy it. I do not disagree with that idea, but it would be nice to know the mechanics and the frequency of such creations, but so far the Gods have not informed us.

I can't think of a way to test the probability of cells absorbing other cells as symbiotes. It appears to have happened once here on Earth, and I get the impression that it was very good for mitochondria, as it was for the eukaryotes that absorbed the, because mitochondria act very well, and they have adapted to their environment. While mitochondria are known to travel through the blood of multi-cellular creatures, they do not seem to attack them.

Even though we eukaryotes have been associated with mitochondria for a few billion years, the mitochondria are not perfectly tied in with your cells, because there are disorders that appear to be connected with genetic mismatches between mitochondria and eukaryotes.

Considering that incompatibility between eukaryotes and mitochondria continues to exist after a few billion years, it might be that those compatibility problems arose earlier and more seriously in other parts of the universe. If the first eukaryotes invaded by a mitochondrion simply digested the thing, then no complex life forms would have developed, until a eukaryotes had the good sense to absorb and use the mitochondria. That took about two billion years here on Earth, but it may take several times as long on other planets. We won't know until we explore the rest of the universe.

I am not the only one who has thought of this. “Radiolab thinks that this merging of two cells was so rare and unlikely that it means that there’s no intelligent life anywhere else in the universe. If life formed on other planets, it probably never evolved past bacteria.”

Then there was the recent story about the first animal found that does not have mitochondria. I am not sure that it is an animal, but that's what the article says. Might complex animals have evolved with symbiotic mitochondria? I can conceive of such things, but I think they would evolve very slowly.

This is something to think about, but the complete answers will not be available, until after we visit many other planets and find only pond scum.