Freethought & Rationalism Archive

Spaz · 03-10-2003, 07:39 PM

Maybe this has to do with evolution, maybe it doesn't, but I can't find out where the hell STDs came from, you know, how they started. It's driving me crazy because that's the first thing I wondered when I learned about STDs and I can never ever find out, AH!

Yeah, so any help would be cool, it's not like I have STDs or something but the question has just been bugging me for years

Doubting Didymus · 03-10-2003, 07:46 PM

Well, they're viruses mostly. Are you just wanting to know where viruses originally came from in general?

Spaz · 03-10-2003, 07:49 PM

well if any virus is transmitted only sexually, where does it start?

Doubting Didymus · 03-10-2003, 08:55 PM

Viruses evolve just like everything else. It may begin as a general all-rounder virus like flu, and evolve more specialised transmission methods later.

Your question is a bit vague, are there any specific barriers you see in the path of STD evolution that you would like addressed?

theyeti · 03-10-2003, 11:32 PM

Which STDs? There are lots of viruses, bacteria, fungi, and even protozoans that can transmited via sexual contact. Why would something evolve to be able to do so?

Well, it's pretty obvious. The parasite doesn't need to wait around in the soil or water for a new host, it doesn't need to encyst (though it might anyway), it doesn't have to survive at a lower temperature, it automatically finds a healthy new host in a nutrient rich part of the anatomy, it has multiple ways into the rest of the body, it is almost always guaranteed an opportunity for a new infection, it needs not bother with the air and the water and the soil and other environmental challenges, and so on and so forth...

Parasites have it good. The ones that get transmitted via sex have it very good.

theyeti

Itzpapalotl · 03-11-2003, 04:16 AM

There is another possible reason why STDs are so sucessful.

The semen of mammals contains a variety of immune system modulating molecules to help sperm evade the maternal immune system and later assist the development of the placenta and foetus.

But this effect could also provide opportunities for a variety of pathogens that are not usually available, so infecting a host in the presence of semen could be much more sucessful than normal, giving an advantage to any pathogen spread this way.

Robertson SA, Ingman WV, O'Leary S, Sharkey DJ, Tremellen KP. Transforming growth factor beta--a mediator of immune deviation in seminal plasma. J Reprod Immunol 2002 Oct-Nov;57(1-2):109-28.

Spaz · 03-11-2003, 05:07 AM

Sorry for being vague, and thanks for info on evolution from some other virus to something sexually transmitted.

Another part of my question is how does an STD find a host before being sexually transmitted? I mean like people aren't born with STDs right? So in order to have an STD it has to be aquired sexually, otherwise it wouldn't be called an STD, no? So how does the first person get an STD? Does random sex with many people just generate an STD or what? Or is it possible to get an STD some other way therefore making it important to call them more than an STD (such as HIV transmitted through blood).

Godless Dave · 03-11-2003, 07:05 AM

Quote:

Originally posted by Spaz
So in order to have an STD it has to be aquired sexually, otherwise it wouldn't be called an STD, no? .

Not really. STDs are primarily transmitted through sexual contact, but (depending on the particular disease) other exchanges of fluid can do it too. I would hazard a guess that the first STDs evolved from diseases that originally transmitted a variety of ways, including sexually, but evolved to specialize in sexual transmission.

Quetzal · 03-11-2003, 07:27 AM

Quote:

Originally posted by Spaz
I mean like people aren't born with STDs right?

Actually, that's not entirely accurate. Many if not most STDs can be transferred from mother to either fetus (like HIV, HEP B, syphillus) or during birth (like chlamydia, gonorrhea). There are also some parasites that can be transmitted this way (like malaria, toxoplasmosis gondii, neosporidia, etc). Basically, a lot of the things that can infect a pregnant woman can infect the fetus or neonate.

As to the rest of the post, evolution of new pathogens and/or new transmission pathways depends on a very complex interaction between the pathogen, host, and environment. Basically, every single thing that afflicts an organism - including STD's - took a variety of evolutionary paths to acheive it's current capability. In the case of STDs, sexual transmission is the way the pathogen evolved to transmit itself. Other diseases use much more complex methods - meaning that there's nothing special about STDs. They just happen to be transmitted during sexual intercourse. No different than a flu virus or cholera.

03-10-2003, 07:39 PM	#1
Spaz Veteran Member Join Date: Feb 2003 Location: 6th Circle of Hell Posts: 1,093	STDs? Maybe this has to do with evolution, maybe it doesn't, but I can't find out where the hell STDs came from, you know, how they started. It's driving me crazy because that's the first thing I wondered when I learned about STDs and I can never ever find out, AH! Yeah, so any help would be cool, it's not like I have STDs or something but the question has just been bugging me for years

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03-10-2003, 07:46 PM	#2
Doubting Didymus Veteran Member Join Date: Jul 2002 Location: East Coast. Australia. Posts: 5,455	Well, they're viruses mostly. Are you just wanting to know where viruses originally came from in general?

03-10-2003, 07:49 PM	#3
Spaz Veteran Member Join Date: Feb 2003 Location: 6th Circle of Hell Posts: 1,093	well if any virus is transmitted only sexually, where does it start?

03-10-2003, 08:55 PM	#4
Doubting Didymus Veteran Member Join Date: Jul 2002 Location: East Coast. Australia. Posts: 5,455	Viruses evolve just like everything else. It may begin as a general all-rounder virus like flu, and evolve more specialised transmission methods later. Your question is a bit vague, are there any specific barriers you see in the path of STD evolution that you would like addressed?

03-10-2003, 11:32 PM	#5
theyeti Veteran Member Join Date: Jun 2001 Location: Denver, CO, USA Posts: 9,747	Which STDs? There are lots of viruses, bacteria, fungi, and even protozoans that can transmited via sexual contact. Why would something evolve to be able to do so? Well, it's pretty obvious. The parasite doesn't need to wait around in the soil or water for a new host, it doesn't need to encyst (though it might anyway), it doesn't have to survive at a lower temperature, it automatically finds a healthy new host in a nutrient rich part of the anatomy, it has multiple ways into the rest of the body, it is almost always guaranteed an opportunity for a new infection, it needs not bother with the air and the water and the soil and other environmental challenges, and so on and so forth... Parasites have it good. The ones that get transmitted via sex have it very good. theyeti

03-11-2003, 04:16 AM	#6
Itzpapalotl Junior Member Join Date: Oct 2002 Location: UK Posts: 12	There is another possible reason why STDs are so sucessful. The semen of mammals contains a variety of immune system modulating molecules to help sperm evade the maternal immune system and later assist the development of the placenta and foetus. But this effect could also provide opportunities for a variety of pathogens that are not usually available, so infecting a host in the presence of semen could be much more sucessful than normal, giving an advantage to any pathogen spread this way. Robertson SA, Ingman WV, O'Leary S, Sharkey DJ, Tremellen KP. Transforming growth factor beta--a mediator of immune deviation in seminal plasma. J Reprod Immunol 2002 Oct-Nov;57(1-2):109-28.

03-11-2003, 05:07 AM	#7
Spaz Veteran Member Join Date: Feb 2003 Location: 6th Circle of Hell Posts: 1,093	Sorry for being vague, and thanks for info on evolution from some other virus to something sexually transmitted. Another part of my question is how does an STD find a host before being sexually transmitted? I mean like people aren't born with STDs right? So in order to have an STD it has to be aquired sexually, otherwise it wouldn't be called an STD, no? So how does the first person get an STD? Does random sex with many people just generate an STD or what? Or is it possible to get an STD some other way therefore making it important to call them more than an STD (such as HIV transmitted through blood).

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