How the placenta evolved from an ancient virus
whyy.org
whyy.org
This reminds me of Lynn Margulis’ discovery that mitochondria and chloroplasts are ancient bacteria incorporated into the cell [2].
[1] https://en.wikipedia.org/wiki/Syncytin-1
[2] https://en.wikipedia.org/wiki/Lynn_Margulis#Endosymbiosis_th...
Gemmata obscuriglobus is pretty interesting, and one could imagine how you go from it to nucleus https://en.wikipedia.org/wiki/Gemmata_obscuriglobus
(Not sure those proteins are also called syncytins in other mammals but I'm not a biologist so I'm using the limited vocabulary I have)
So some sharks have placentas, as mentioned in this article about tiger sharks secondarily losing theirs: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4906603/ I wonder if I'll ever run out of huge, obvious questions I haven't even begun to explore.
[..] There are over 500 species of shark living in waters around the world and the majority give birth to live young. The remainder are oviparous, meaning they lay eggs. [..]
[..]Whale sharks (Rhincodon typus) are the largest species of shark. Although these animals produce eggs, they don't lay them. Instead, the young hatch while still in the female's body and are born as miniature adults. This is known as ovoviviparity.[..] In some species, the female will produce unfertilised eggs, which are eaten by embryos. This is known as oophagy ('egg eating') and occurs in species including the shortfin mako (Isurus oxyrinchus) and bigeye thresher sharks (Alopias superciliosus).
Embryos of other sharks survive by feeding on their smaller siblings. This is called intrauterine cannibalism or sometimes as embryophagy ('embryo eating'). This is known to occur in sand tiger sharks (Carcharias taurus).
Placental viviparity occurs in some species of shark - once the yolk sac has been depleted, it attaches to the uterine wall, acting as a pseudoplacenta.[..]
Also led me to this interesting article on the Basking shark which has an absolutely gigantic mouth for filter feeding plankton.
https://www.nhm.ac.uk/discover/basking-shark-cetorhinus-maxi...
The Leviathans..city sized sentient whale like creatures that replicate by splitting themselves ..a process called ‘budding’. A very enjoyable read. This thread made me look it up to read again. If you like good old fashioned sci-fi, I recommend it. It’s part of Ben Bova’s Grand Tour series.
Edit: Looks like it's merely relative size, and when neither gamete is bigger biologists throw up their hands. Sort of a bummer that there isn't a more robust definition.
Also note that sperm vary in shape. Mammalian sperm have the familiar tadpole shape with a flagellum for swimming. Other species, such as nematodes, have ameboid sperm which move along surfaces rather than swimming freely.
I think this is wrong. My understanding is that the sperm cell membrane fuses with the egg cell membrane, forming a single container. The haploid nucleus of the sperm and the haploid nucleus of the egg then fuse. This processes is by no means fully symmetric (the egg has a tough coating on its cell membrane that must be dissolved by the sperm through the Acrosome reaction), but there is also no time when the sperm cell (delineated by its membrane) is inside the egg cell.
https://en.wikipedia.org/wiki/Acrosome_reaction
My point was not that there aren't many correlated asymmetries between eggs and sperm in particular parts of the phylogenetic tree (like mammals) that can be used for distinguishing them. My point was that there seems to be no fundamental asymmetry that applies to all two-sex sexually reproducing organisms; rather, there is a continuum of degree of gamete dimorphism that ends at organisms where there is no principled distinction between sperm and egg (isogamy).
Fun fact: "About 8 percent of human DNA comes from viruses inserted into our genomes in the distant past, in many cases into the genomes of our pre-human ancestors millions of years ago." https://newsroom.uw.edu/news/genes-%E2%80%98fossil%E2%80%99-...
Endogenous retrovirus Wiki page: https://en.wikipedia.org/wiki/Endogenous_retrovirus
Assuming a low percent of the infected get their genome changed or produce offspring with altered genome, those don't take over.
I'm not familiar with this topic at all, but it's super interesting.
In the case of HIV it's even worse since it targers certain immune cells. It will eventually kill most of them if it's allowed to replicate unchecked, crippling its host's immune response.
Viruses aren't actual living beings, they're just self-replicating structures. They are capable of injecting genetic material into other cells in order to get them to make more copies of themselves.
> Pathological viral infection feels like an infinite loop.
The same logic could be applied to biochemistry in general. It's not 100% accurate but it is a lot of fun to think about it in those terms. It's also fun to think about programming in biochemical terms! I wrote about this in the past:
Something like:
Biological immortality means after some point mortality rates don't increase with age - you can still grow old, it just won't directly kill you. Biologically immortal organisms don't have a max lifespan, if they're lucky they can just keep on going, but they may be dramatically more feeble than their younger counterparts.
When it comes to viruses though, there's one more very fascinating hypothesis. That the cell nucleus itself was once actually a virus that took over some bacteria to do its bidding.
endogenous
- having an internal cause or origin.
- growing or originating from within an organism.
Genous, you can think of it as analogous with genesys, it's the root word for creation.
No virus needed. Humans are currently (or were very recently) under enormous evolutionary pressure to get smarter. The ability to adapt is likely itself a trait as you suggest, but it makes sense that it can vary over time as needed depending on environmental factors.
Thus we have some species nurturing their young (most mammals, marsupials, and birds) as opposed to spawning them and then going on to other things (e.g. fish, insects).
The most extreme case of this is humans: females live well beyond their fertile age and, effectively, so do men (while technically fertile in their 70s, the offspring are not as vigorous, in the evolutionary sense, as those conceived when the father was in his 20s). It is believed that this is because older humans have learned lots of things that can be useful in keeping kids alive and effective until they can propagate their genes.
Although 99+% of evolutionary psychology is utter bullshit this is nonetheless fascinating.
Either way, I would like to thank user dragosmocrii who lead me to this article via their comment at https://news.ycombinator.com/item?id=25655272
Not hoping to be in a distopic yet magic world.
Some sharks can have so-called 'virgin' births.
In the case of viruses, remember that there are viruses for much simpler organisms, like bacteria. And yes, you can use those to treat bacterial infections.
Those are called bacteriophages (a misnomer, since they don't actually eat bacteria).
I have a theory that bacteriophages originated as a biochemical weapon for inter-bacterial competition.
If you think about it, the ability to produce packets that target and penetrate a competitor's cellular wall and inject a payload is pretty useful. Payloads could be as simple as a toxin to start.
From that point, you could have stepwise improvements for deliverables that disrupt reproduction in the target (for example by cutting apart DNA strands), by inserting junk genetic material to evade self repair mechanisms, by inserting or removing specific genetic sequences to create other vulnerabilities, that insert the specific genes to make copies of the delivery system and various payloads (this is useful even if the 2nd gen copies are poor and don't include those same genes), and then finally a fully self-reproducing package that can spread exponentially.
At that point the 'weapon system' can evolve independently, and indeed co-evolve with it's target/host to (probably) jointly outcompete other species including the originating species.
Even prior to full self-reproduction, proto-viroids might act as a horizontal gene transfer mechanism that can exhibit familiar 'selfish gene' patterns and mediate various feedback loops between bacterial species. After 'escape' any species remaining with proto-viroids mechanisms would likely be parasitized and bootstrapped into actual viruses through competition and crossovers, or have those mechanisms suppressed into remnants indistinguishable from endoviruses (presuming endoviruses can even be identified in organisms as simple as bacteria).
An arms-race of proto-viroid attack vectors might also be the antecedents of and/or the driving force behind the need for various organelles that distinguish the more complex eukaryotes from bacteria.
I think that's wrong. By definition, a parasite interacts with a living organism. For example worms that eat the remnants of fallen leafs are not parasites, they are saprophytes. Humans as well can live consuming bits of fallen fruits that do not take part in plants' further reproduction (i.e. fruit's seeds) and would otherwise just rot (and can thus be considered dead tissue).
https://www.frontiersin.org/articles/10.3389/fmicb.2019.0052...
Who is to say that viruses won't be the end result of life on the planet earth?
Complex life <> more evolved life. It's just differently evolved.
The way I imagine my idea is that, if you pick a species and its interesting descendants, and order on a timeline like such:
A --> B --> C --> D
[bunch of other spinoffs]
^
|
A --> B --> ...
https://en.wikipedia.org/wiki/Nucleocytoviricota
However, none of them seem to be related to anything on the official tree of life.
There must be some way to do it, because I constantly encounter people on the Internet, that know everything, and are good at everything.
I can’t get any of them to tell me how they do it, though...
I would have guessed that the virus imparted the DNA at some earlier point, and that DNA helped a placenta evolve.
So they don’t need to spend all that tax payer dollars on researching this.
God made man. End of story.
Seems like a very reasonable hypothesis if that virus is a retrovirus [1]:
> Endogenous retroviruses (ERVs) are endogenous viral elements in the genome that closely resemble and can be derived from retroviruses.
> ...not all ERVs may have originated as an insertion by a retrovirus but that some may have been the source for the genetic information in the retroviruses they resemble.
Not really: https://www.liebertpub.com/doi/10.1089/088922299309810
Besides, the closest equivalent in software is:
If you have ~20 lines of code, written twice with the same function (perhaps crossing multiple functions in the same order), written with identical style and syntax, with maybe some variable names being slightly different.
In a copyright case, would you believe that these originate from different authors?
For lots of ho-hum reasons that don't require any spectacular justification, you are full of virus DNA -- it's just mostly never mentioned in popsci articles that come under your skeptical lens :)
Please do not mistake this comment as antivaxx nonsense, the article linked discredits both the theory and the scientists who started it all.
I couldn't find anything stronger than "german doctors say" which means nothing.
That's all there is to it.