this post was submitted on 12 Jun 2025
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Showerthoughts
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A "Showerthought" is a simple term used to describe the thoughts that pop into your head while you're doing everyday things like taking a shower, driving, or just daydreaming. The most popular seem to be lighthearted clever little truths, hidden in daily life.
Here are some examples to inspire your own showerthoughts:
- Both “200” and “160” are 2 minutes in microwave math
- When you’re a kid, you don’t realize you’re also watching your mom and dad grow up.
- More dreams have been destroyed by alarm clocks than anything else
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- All posts must be showerthoughts
- The entire showerthought must be in the title
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- If your topic is in a grey area, please phrase it to emphasize the fascinating aspects, not the dramatic aspects. You can do this by avoiding overly politicized terms such as "capitalism" and "communism". If you must make comparisons, you can say something is different without saying something is better/worse.
- A good place for politics is c/politicaldiscussion
- Posts must be original/unique
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Yep, literally every single living thing has a common ancestor.
Monkey? Yep.
Tree? Yep.
Octopus? Yep?
Mushroom? Yep?
Bacteria? Yep.
What if a bunch of the earliest life spontaneously formed by the millions independently in different places? Would we all really have a true single common ancestor then?
Edit: I think there's been a misunderstanding. I believe that all life on earth came from the same "species", being the same kind of structure spontaneously generated in the primordial soup, but that there could've been a number of those structures that were generated and were all identical to each other. This would mean that any of them could evolve from the same starting point in terms of "design", but not literally be the exact same object, meaning that we could have a number of origin ancestors that were all identical, and were potentially not an exact one singular living thing.
There are a bunch of characteristics that, while fairly arbitrary, can't be changed once they are locked in. The mappings from RNA to proteins are a good example. Changing it is instantly lethal to the cell involved. Others include the chirality of amino acids, and the choice of bases for DNA.
If we look at the entire tree of life, we see no deviations in these deep characteristics. This implies that they were fixed before we all split. There might have been alternative variations in the past, but none have survived to the modern day (that we have identified).
This goes double of eucaryotes (basically everything other than bacteria). The design is so unique that convergent evolution is highly unlikely to stumble into the exact same layout from 2 sources.
Ah, alright that's a fair point. Once one of those splits happened then that single life form would have become the common ancestor for all other life. I'm satisfied with that explanation.
Some (probably bacteria-like) form of life appeared almost as soon as conditions made it possible, so it’s conceivable that it arose multiple times in earth’s history. But eucaryotes (animals, plants, and fungi) took almost half the lifetime of the earth to appear, and have a lot of contingent features, so it’s overwhelmingly likely that all eucaryotes have a common ancestor.
It's almost a certainly that all current life on earth has the same common ancestors. It makes sense for a ton of reasons.
For example all living organism have dna, and they all use the same 4 nucleic acids that their dna is made from. Neither of those facts are necessary requirements for life to exist, so since 100% of life does both of those things then that's very strong evidence that 100% of life had a common ancestor.
https://en.m.wikipedia.org/wiki/History_of_life
https://en.m.wikipedia.org/wiki/Last_universal_common_ancestor