Just learned the other day – was it here? – that the only time you get a male tortoiseshell cat is when they’re XXY, because you need 2 Xs to make the trait dominant.
So, what’s the equivalent for human males? What almost never happens with males unless they’re XXY? Human torties would be great, but I doubt we’re that lucky as a species!
I’ve long posited that humanity is the yeast in galactic beer-reproducing as rapidly as possible, consuming everything in the environment, and then dying in our own excretions.
I have to admit, this one struck me because I did my senior seminar in biology on “Endosymbiosis and the Origin of the Eukaryotic Cell” inspired largely by Lynn Margulis’ work. That was 1986! That fact that all these years later this is still cutting edge stuff is kinda mind-blowing.
Something personally frustrating, though, is that so much of this work is still using Woese’s tree with three separate domains – Bacteria, Archaea, and eukaryotes. You can see here where they talk about membranes, saying because eukaryotes don’t have archaea-like membranes they couldn’t have been inherited.
Where I have seen that checked, though, it usually comes out that there’s a good chance bacteria are ancestral to the other two. In particular some new research put them very close to Planctomycetes, so originating somewhere high among the branches of the bacterial tree instead of at its base. What does that mean for talk about foreign genes like this? I’m not sure, but it’s a big difference and I suspect it’s important.
I have been very excited about the discovery of the Asgardian biota and the strong indication that this is the closest we will get to our eukaryotic LCA. I have also been frustrated at the slow progress, but that is to be expected.
As an aside, I have been equally fascinated by this discovery dating back to the 2010’s, and frustrated that there is no progress on proving or disproving it.
(I choose to believe that these critters hang on in the deep sea, but, well, I also cling to the increasingly unlikely possibility that comb jellies are surviving Ediacarans, so…)
Actually, there had been progress on Dendrogramma, which now seems pretty well placed:
I think the general consensus is that Ediacarans are probably not all one thing. I could believe some of them are related to comb jellies. Modern comb jellies are actually a very recent group – the last common ancestor is apparently somewhere around the start of the Cenozoic – which makes them difficult to compare to, but there was a recent paper linking them to some Cambrian polyps:
They mention Ediacaran Eoandromeda as maybe similar, but it is very much a maybe…pretty much all you can easily say about it is that whatever it was, it had octagonal symmetry.
https://sciencenordic.com/biology-denmark-natural-sciences/who-came-first-sponges-or-comb-jellies/1729497
Suggesting that comb jellies might predate Porifera. Not sure how to interpret it entirely. But very interesting. The seemingly indepenent evolution of very different neural tissues and transmitters is at the very least weird.
On the ediacaran/siphonophore, all i can say is bummer, man. I was holding out hope there.
Not enough to know that some siphonophores are so strange you can mistake pieces of them for something new?
I’m not entirely sure what to make of the comb jelly papers either. Personally I’m…skeptical. The results seem to be based purely on gene trees, but those have a known risk of long branch attraction, where very modified groups can be misplaced on the outside of the tree. And comb jellies are a really bad case for that, because like I said all the living ones diverged recently, so most of their history is effectively unrepresented.
That said, morphology can be misleading too, especially when the features are so simple they could easily converge. So for instance finding out they have their own set of neurotransmitters is really interesting…it might not argue for them predating sponges, but definitely suggests they don’t belong say next to Cnidaria like the fossil paper shows. For sure something to look forward to finding out more about.
Yeah, the initial “living ediacaran” paper (i can’t believe that was back in the '80s! Damn, I’m old) was entirely based on morphology. I am not shocked that hypothesis fell through. Bummer, but hardly shocking. No, my “not sure how to interpret” comment was about the comb jelly papers. These seem pretty esoteric, and i am waiting for people way smarter than me to sort out the details. Interesting, for sure, but extraordinary claims and all.
Measuring around a centimeter long, they are roughly the size and shape of a human eyelash, batting away the competition at 5,000 times the size of garden-variety bacteria and 50 times the size of bacteria previously considered giant. In human terms, this is akin to coming across a person as tall as Mount Everest.