Comment on What can we learn from this prehistoric organism with no anus?
sj_zero 2 years ago
They come to the conclusion in the article that it could not possibly be a common ancestor with humans, but I don't know how they could necessarily come to that conclusion. Billions of years are a long, long time.
Not gonna pretend it looks like something that would be a common ancestor with us intuitively, but when you get that far back I don't know...
Sal@mander.xyz 2 years ago
The paper can be found here: https://drive.google.com/file/d/13PcNRqAZQ5frLajaP2V7UDH3NzDRLCQ6/view
The wiki page also has a summary of this topic: https://en.wikipedia.org/wiki/Saccorhytus
These fossils were discovered in 2017, and are dated to be about 540 million years old. The guys that originally discovered pointed out that the morphology of this organism had similarities to the embryos of the group of animals that humans belong to, suggesting that it could represent an evolutionary ancestor.
In this paper, what the researchers did was to look at the morphology more closely by using more powerful microscopy techniques, and they reached a different interpretation. According to them, these organisms actually belong to a group of animals that is known to have split from our evolutionary branch a while ago. So, these belong to a "sister" group and not to an ancestor.
Here is the image in the paper where they show the evolutionary relationship on the basis of the morphology as they interpret it. This 'Saccorhytus' is shown in red, and the group that contains the humans (Deuterostome) in green:
Image
sj_zero 2 years ago
Ah, so the key here is that the fossil record is probably more complete than I'd expect.
A few years I went down the rabbit hole of geology and palaeontology, and the thing I had trouble wrapping my head around was the incomprehensibly long time scales involved, and how there's a massive amount of stuff from different eras, but timescales that long have a tendancy of homogenizing the evidence out of existence because there's just so much stuff smushed together.
Sal@mander.xyz 2 years ago
Yeah, the scale is just so massive compared to our lifetimes and the history of humanity. I get that feeling to with astronomy, where distances are just so massive and our planet such an insignificant tiny wet rock.