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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

#101

Post by gumby »

andromeduck wrote: post #98
mgalgs wrote: post #97

Earlier quoted context omitted.

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

By reducing cycle time and resource competition between generations.

And the unusual factor that certain species adopted an intergenerational social system (which makes longer lifespan slightly more advantageous).

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.

Re: How the placenta evolved from an ancient virus

#102

Post by restalis »

olau wrote: post #13
johnnujler wrote: post #9

Every thing about life is so fascinating. I have always wondered how viruses have persisted for so long if they need a host to survive and it took us millions of years to go from single celled to multicellular. I wish there was a way to know everything and become good at everything. :/

I think the plain answer is that if they didn't, you wouldn't know about them. Just like all other parasites. In some sense, we're all parasites on plants, that in turn feed on the energy delivered by the giant fusion reactor in the middle of our solar system. 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.

"In some sense, we're all parasites on plants, that in turn feed on the energy delivered by the giant fusion reactor in the middle of our solar system."

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).

Re: How the placenta evolved from an ancient virus

#103

Post by kridsdale1 »

jjk166 wrote: post #72
ckosidows wrote: post #52

Earlier quoted context omitted.

I thought the term was negligible senescence?

They're similar but distinct concepts. Negligible senescence means after a point aging doesn't negatively affect the organism. They don't lose reproductive capability or experience functional decline. Imagine being 20 forever. 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…

I think some Lobsters and Crocodiles are in the later category. Immune to cancer, their cells divide without limit over the years. So they never stop growing. The enormous ones are the oldest, and have a size fitness advantage in hunting and other combat, but a counter balancing fitness disadvantage in their increased needs.

Re: How the placenta evolved from an ancient virus

#104

Post by kridsdale1 »

n0rbwah wrote: post #100
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'…

How do we know it happened many times, vs a single ancient origin with non-lethal random mutation experienced by different branches since then?

Re: How the placenta evolved from an ancient virus

#105

Post by kridsdale1 »

matheusmoreira wrote: post #61
studiecomput wrote: post #47

Earlier quoted context omitted.

Another wild thought: Is it possible that the solution for harmful retroviruses, like HIV, are retroviruses itself? If retroviruses can overwrite or fuse with our DNA, can't we overwrite it back by making a retrovirus ourselves? I'm not familiar with this topic at all, but it's super interesting.

The problem with pathological viruses is they take over the cells themselves and make them fabricate more viruses until they burst. In these cases there is no living cell left to reprogram. 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.

Pathological viral infection feels like an infinite loop. The CPU is a dumb machine doing its job to decode and execute instructions, until it bursts in to flames. The ribosome likewise transforms amino acids in to proteins as directed by RNA until the cell is destroyed.

Re: How the placenta evolved from an ancient virus

#106

Post by kridsdale1 »

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?

They don't need to provide a benefit. They only need to not reduce fertility.

Re: How the placenta evolved from an ancient virus

#107

Post by kridsdale1 »

restalis wrote: post #102
olau wrote: post #13

Earlier quoted context omitted.

I think the plain answer is that if they didn't, you wouldn't know about them. Just like all other parasites. In some sense, we're all parasites on plants, that in turn feed on the energy delivered by the giant fusion reactor in the middle of our solar system. 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.

"In some sense, we're all parasites on plants, that in turn feed on the energy delivered by the giant fusion reactor in the middle of our solar system." 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'…

Fruit eating is a case of symbiosis.

Re: How the placenta evolved from an ancient virus

#108

Post by matheusmoreira »

kridsdale1 wrote: post #105
matheusmoreira wrote: post #61

Earlier quoted context omitted.

The problem with pathological viruses is they take over the cells themselves and make them fabricate more viruses until they burst. In these cases there is no living cell left to reprogram. 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.

Pathological viral infection feels like an infinite loop. The CPU is a dumb machine doing its job to decode and execute instructions, until it bursts in to flames. The ribosome likewise transforms amino acids in to proteins as directed by RNA until the cell is destroyed.

Yes. Ribosomes are dumb machines. They have no authentication mechanism. The RNA randomly gets near the ribosome, interacts with it and the result is a whole new protein. It doesn't know whether the RNA was translated from cellular or viral DNA. In the case of cellular DNA, the ribosome makes useful proteins that helps the cell perform its function. In the case of viral DNA, the ribosome makes viral proteins which eventually get assembled into a new copy of the virus.

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:

https://news.ycombinator.com/item?id=21562716

Re: How the placenta evolved from an ancient virus

#109

Post by oblio »

BurningFrog wrote: post #68
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/

Since I had to look it up... endogenous - having an internal cause or origin. - growing or originating from within an organism.

Endo is internal, exo is external. Another example is endonym/exonym (nym is the particle for name): endonym - the name a group gives itself, exonym - the name outsiders give a group.

Genous, you can think of it as analogous with genesys, it's the root word for creation.

Re: How the placenta evolved from an ancient virus

#110

Post by studiecomput »

matheusmoreira wrote: post #108
kridsdale1 wrote: post #105

Earlier quoted context omitted.

Pathological viral infection feels like an infinite loop. The CPU is a dumb machine doing its job to decode and execute instructions, until it bursts in to flames. The ribosome likewise transforms amino acids in to proteins as directed by RNA until the cell is destroyed.

Yes. Ribosomes are dumb machines. They have no authentication mechanism. The RNA randomly gets near the ribosome, interacts with it and the result is a whole new protein. It doesn't know whether the RNA was translated from cellular or viral DNA. In the case of cellular DNA, the ribosome makes useful proteins that helps the cell perform its function. In the case of viral DNA, the ribosome makes viral proteins which ev…

This is an awesome topic. Thank you both for your response! I try to convert everything into programming terms to make it a bit easier to understand, but it's a really complex topic imo.
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