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How the placenta evolved from an ancient virus

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Re: How the placenta evolved from an ancient virus

#91

Post by jelliclesfarm »

dr_orpheus wrote: post #79
jelliclesfarm wrote: post #20

Earlier quoted context omitted.

Sharks are viviparous, oviparous and also ovoviviparous. [..] 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…

Thank you for this link on how sharks give birth. I never thought the subject would be so fascinating. 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...

I remember that! Also whales do that too iirc.

Re: How the placenta evolved from an ancient virus

#92

Post by f6v »

pps wrote: post #60
jgilias wrote: post #30

It is also being researched how endogenous retroviruses are part of aging. The very rough idea being that at some point long in past a retrovirus became endogenous and provided a pathway for aging increasing the evolutionary rate of that organism, which would then out-compete most of the immortal organisms with time. Something like: https://pubmed.ncbi.nlm.nih.gov/20346965/

That's incredibly interesting! Do you know some (pop)science books that could help learn more about viruses? I found two that sound good from description: "Viruses: A Very Short Introduction" by Dorothy H. Crawford and "A Planet of Viruses" by Carl Zimmer. Would you recommend any of these or something else?

Red queen gives some perspective on evolutionary arms race between hosts and pathogen. Virus is a piece of genetic material, so to understand a virus one needs to understand how a gene evolves.

Re: How the placenta evolved from an ancient virus

#93

Post by remram »

klyrs wrote: post #86
remram wrote: post #50

Earlier quoted context omitted.

That would probably only work if it gave the altered species a significant advantage (or if you had a system to detect and penalize/eliminate individuals depending on their genome, at scale).

At this point in time, do you really think that viruses are incapable of sweeping the globe and infecting a significant fraction of humanity, if they don't provide a benefit to the host?

The parent was more specific and asked about changing a species's genome. Infecting everyone does not lead to a change in genome if they die (or fight it off).

Assuming a low percent of the infected get their genome changed or produce offspring with altered genome, those don't take over.

Re: How the placenta evolved from an ancient virus

#94

Post by f6v »

jessriedel wrote: post #76
chongli wrote: post #59

Earlier quoted context omitted.

The relative size but also the structure and the process of fertilization. The sperm enters the egg, not the other way around. Mitochondria come from the egg, yes. 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.

> The sperm enters the egg, not the other way around. 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…

I red this in some book I forgot the name of, so I can’t cite anything. But it was explained that female strips everything except for the DNA from sperm. This way there’s minimal risk of infecting the egg with the pathogens the sperm can carry. I’m not sure if it’s true just for humans or other organisms as well.

Re: How the placenta evolved from an ancient virus

#95

Post by f6v »

What’s fascinating is that genome is highly dynamic. The transposons rearrange themselves all the time and are believed to be remnants of ancient viruses. And there’s probably many more pieces of DNA which are domesticated viruses. Alu element comes to mind, which is the most common transposable element in human genome and probably has a role in regulating gene expression.

Re: How the placenta evolved from an ancient virus

#96

Post by fastaguy88 »

I think this article is a bit misleading. The placenta did not evolve from an ancient virus. A protein found in primate placentas (but, interestingly, not found in other placental mammals) is clearly related to endogenous retrovirus proteins. (I do not think that HERV and HIV have much to do with each other -- they are very different viruses). But it is pretty interesting that primates started using this protein relatively late in mammalian evolution.

Re: How the placenta evolved from an ancient virus

#97

Post by mgalgs »

jgilias wrote: post #30

It is also being researched how endogenous retroviruses are part of aging. The very rough idea being that at some point long in past a retrovirus became endogenous and provided a pathway for aging increasing the evolutionary rate of that organism, which would then out-compete most of the immortal organisms with time. Something like: https://pubmed.ncbi.nlm.nih.gov/20346965/

I'm confused... How does aging speed up the evolutionary process?

Re: How the placenta evolved from an ancient virus

#98

Post by andromeduck »

mgalgs wrote: post #97
jgilias wrote: post #30

It is also being researched how endogenous retroviruses are part of aging. The very rough idea being that at some point long in past a retrovirus became endogenous and provided a pathway for aging increasing the evolutionary rate of that organism, which would then out-compete most of the immortal organisms with time. Something like: https://pubmed.ncbi.nlm.nih.gov/20346965/

I'm confused... How does aging speed up the evolutionary process?

By reducing cycle time and resource competition between generations.

Re: How the placenta evolved from an ancient virus

#99

Post by astrange »

TeMPOraL wrote: post #39
mrunkel wrote: post #28

Earlier quoted context omitted.

This implies that evolution has a goal and that we are that goal. This shows a fundamental misunderstanding of evolution of natural selection that is common. 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.

I know that evolution doesn't have a goal. I may have antropomorphosized it too much, but my goal was to follow a sort of temporal/casual trail that we find interesting. 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 What really happens is more like: [bunch of other spinoffs] ^ | A --> B --> ... And that some of those sp…

There are some viruses that are so large they're as complicated as actual living things.

https://en.wikipedia.org/wiki/Nucleocytoviricota

However, none of them seem to be related to anything on the official tree of life.

Re: How the placenta evolved from an ancient virus

#100

Post by n0rbwah »

sradman wrote: post #55

Magnificent. The placenta uses a protein named syncytin [1] to attach to the cells of the uterus. This protein is expressed by a retrovirus that was integrated into animal DNA over 100 million years ago. 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_…

Fun fact, Syncytin-1 is the syncytin used by primates, other branches of mammals have other forms of syncytins, meaning that the event of being infected by a retrovirus that gives mammals proteins necessary for the placenta happened several times in history following the original event and replaced the original syncytin.

(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)

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