No, I wasn’t stoned. This thought was inspired by the post the other day about how trees evolved independently (e: multiple times) from different plants, the product of convergent evolution.
No, I wasn’t stoned. This thought was inspired by the post the other day about how trees evolved independently (e: multiple times) from different plants, the product of convergent evolution.
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?
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.
It’s almost a certainly that all current life on earth has the same common ancestors. And it makes sense very solidly for a lot 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
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.