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The Role of Retroviruses in Human Evolution
mhackarbie writes "The current edition of the New Yorker magazine has up a story about endogenous retroviruses in the genomes of humans and other species. Although researchers have known about such non-functional retroviral 'fossils' in the human genome for some time, the large amount of recent genomic data underscores just how pervasive they are, in a compelling tale that involves humans, their primate cousins, and a variety of viral invaders. Some researchers are even bringing back non-functional viral remnants from the dead by fixing their broken genes."
So what you're saying is we will now have zombie viruses?
We will bankrupt ourselves in the vain search for absolute security. -- Dwight D. Eisenhower
Obviously if enough individuals survived with cells reproducing its DNA containing the retrovirus for it to become a species-wide "fossil" it was either not very harmful or possibly even beneficial to our ancestors. You might be able to make the case that perhaps we have since lost the ability to combat these retroviruses, but then we must consider the possibility that in some individuals these portions of dormant virus data have been reactivate naturally. If this has occurred and we are indeed now ill equipt to fight it, then it would have been observed as some disease and possibly classified as a genetic disorder. Who knows, by reactivating these, we have discover the cause, and subsequently the cure (as obviously we naturally beat it once) to some terrible genetic malady!
Demented But Determined.
How do we know the the retrovirus genome didn't originate with the hosts themselves? Did these viruses evolve truly independently, or might they have started out as fragments of genetic code from some larger organism which somehow escaped and became self-sufficient?
In other words, when we look at the human genome and say, "This is riddled with retroviruses!" is it not possible that the retroviruses were actually there all along, and only later became able to leave the parent cell and operate independently?
Are retroviruses actually just chunks of "rebel DNA" from our own genome, or possibly from some other species?
What you're describing is probably possible, but for any given stretch of DNA encoding the right polymerases, it's a lot more likely that it's a retrovirus that lost the ability to leave the cell than that it's a transposon that gained that ability and then lost it again.
Is what I meant to say.
The correlation between ignorance of statistics and using "correlation is not causation" as an argument is close to 1.
Such viruses may be responsible for the Cambrian Explosion. A new kind of virus may have helped "share good ideas" like eyes, nervous systems, enzymes, etc. between different species of early animals. This may have propelled evolution by allowing life to mix and match instead of each branch having to reinvent stuff from scratch.
Table-ized A.I.
If we "fix that part where they're drug resistant", it would make no difference, unless we could eliminate those viruses in the first place. It's like trying to populate the world with only mice that were more likely to get caught in traps. It would only be possible if we could eliminate all the mice in the world, and then introduce these 'dumb' mice into the wild. What's the point of repopulating the world with dumb mice if we didn't want mice in the first place?
Second of all, if you read the article, you would know how the researchers 'fixed' the 'broken' viruses:
The team took ten versions of that virus (we carry more than thirty) and compared the thousands of nucleotides in the genetic sequence of each version. They were almost identical, but where they differed the researchers selected the nucleotides that appeared most frequently. That permitted them to piece together a working replica of the extinct retrovirus. "If you have a person with a lethal defect in the heart,'' Bieniasz explained, "and another with a lethal defect in the kidney, you could make one healthy person by transplanting the respective organs. That is what we did.Lastly, and not that it will necessarily assuage your fears, but a species that carries an endogenous retrovirus in its genome is far less likely to be infected by that virus. Some developmental biologists employ a well-characterized and naturally occurring chicken retrovirus, engineering it to misexpress a normal chicken gene of their choice. This way, they can see what happens if they express that gene everywhere within a developing organ, as opposed to the normal expression of the gene only within a small population of cells within that organ. (As an example, they are studying gene X, which plays a role in bone development, and is only expressed in cells that will become bone cells. They make a chicken retrovirus that also expresses gene X, and infect the wing of a developing chicken. Now all the cells in the wing express gene X, and not just those that were going to become bone cells.) In order to do this, these researchers must use eggs from chickens that do not carry endogenous copies of this virus in their genome. Eggs from chickens that carry endogenous copies of this naturally-occurring retrovirus in their genome are far less susceptible to infection by the engineered virus, and therefore are not experimentally useful. Such endogenous retrovirus-free chickens were specially bred.
Sure, there are always potential risks from any type of science. But it is important to know how risky something is, and weigh that versus the potential benefits.
From what I was just reading now, maybe the RNA world which some theorists have speculated (theorized) predated the DNA biological world we presently live in was the place where something like viruses could reproduce themselves.
But I'm probably misunderstanding everything I read today.
My personal opinion?
I remember playing with a 6802 prototyping board with a flaky power-on reset circuit. (I used cheap switches from Radio Shack.) It had a monitor ROM, of course, then later it had BASIC in ROM. If power came up too fast, the ROM would not be ready to put the reset vector on the bus, and the CPU would jump somewhere else. Sometimes, if the reset button worked, I could look at RAM, and I would find bits and pieces of the ROM sitting out there. Until the thing stabilized, sometimes it was not particular interesting, but sometimes it would dump almost intelligible strings, or even clots of error messages or the symbol tables into video RAM.
I had read, at the time, about how computers with disk drives had to have good power-on reset circuits, or had to be booted up with no media in the drives, and media loaded after the operator stabilized the CPU. Otherwise, the disk drives would tend to get told to write random data on the disks, which, of course, kind of ruins the whole purpose of having disks.
I had also read that (some of?) the first computer viruses were inspired by some of the junk that was left in memory by such episodes of uncontrolled execution.
So I have tended to wonder whether it might not be the case that viruses are not some independent remnants of proto-life, but are rather the results of genetic accidents.
I'm not sure we could tell the difference from looking at the archeological record.
But it's interesting that one of the biologists the friendly article quotes made a comment that almost equated viruses with God.