HERV: A key factor in our Evolution?

[Mentat]

Obviously we cannot deny that gradual evolution occurs. This is obvious, and readily demonstrable. However, there are some apparent "gaps" in the fossil record (which creationists are quick to jump on as evidence of God's having created the different "kinds" individually) that lead one to think that there may be something other than the gradualist approach.

Greg Bear wrote the books, Darwin's Radio and Darwin's Children (a science fiction novel and it's sequel respectively), and in them he proposes that ERV, or endogenous retroviruses, may be the "messengers" of evolution.

A retrovirus (as I'm sure most of us know) is a virus that is encoded into a host's DNA. An endogenous retrovirus would be a retrovirus that is not infection laterally but only passed on through the generations, in the genes.

Now, if these ERV are encoded in the genes that we pass on to our children, it is reasonable to assume (as Greg Bear did in his books) that the virus may contain information - gathered from previous mutations of species - on what is a "beneficial" mutation, and could express itself, if put under enough stress.

This approach would explain, not only fossil record "gaps", but also the fact that experiments (such as the introduction of a toxin into a colony of fruit-flies) have shown drastic evolutions, in response to stresses, that express themselves in just one or two generations.

Any/all comments are appreciated.

 

[Mentat]

BTW, I asked about HERV (human endogenous retroviruses) in the title, but am really open to discussion of all ERV.

 

[iansmith]

first, ERV are RNA virus that, once their genome is reverse transcribed into DNA, can integrate their genome into their host genome. There some old ERV viruse present in our genome. (http://www.nature.com/cgi-taf/DynaPage.taf?file=/ng/journal/v21/n3/full/ng0399_257.html).

The present of an integration can lead to many routes. The integration could cause an insertional mutation in a gene (i.e. the gene get knocked-out). The genomic integration could also be in "useless" (in relative term) part of the host genome creating no problem. These knock-outs, if beneficial, could explain some "gaps" in the fossil record.

I don't known how precise ERV can extract their genome out of their host. If some ERV are "slopy" (some viruses insert by accident host genes into their genome) and the ERV can cross species, genes could be transfert to one species to another. If this phenomen happens then it can explain some quantum leaps in term of evolution. The promoter and inhibitor of the gene should also be compatible with the new host. If it is not compatible, then the gene migth not express properly.

According to me, Greg Bear is forgetting that we only find some missing links and we have not identify all the species that have and are living.

I also think that the relation between stress factor and evolution is a joke. Experimentally we can isolate bacteria that are randomly resitant to antibiotic and no endogenous virus are found in their genome. Fruit fly can reproduce fast and generation can be randomly resistant to toxin.

ERV could explain some gaps but Greg bear example have flaws and are not the best.

 

[CrystalStudios]

Mentat - Being a biologist, I must make a comment about the presumption of your post.

Every single year hundreds of the phylogenic holes are filled. Ten years ago there were thousands less links and more empty spots than there are now.

I have found 100% no need to attribute the holes to anything other than the fact that we as humans have yet to fill them in.

The phylogenic tree is somewhere around 90+% completely.

So for any theories to arise to explain these holes other than the fact that we haven't found all the fossils we need yet are completely absurd.

It's just an absurd thought. It's like having to look around an entire room for microscopic parts to a puzzle, and continuing to find one after another, and at some point stopping to say - I have a theory why there is holes, because some pieces are mizzing - when it's obvious that at your current rate of filling it in their is a distinctly short period of time until the puzzle is complete.

See what I mean? Any such other claim is absurdity as absurd as creationism.

 

[Mentat]

Originally posted by CrystalStudios
Mentat - Being a biologist, I must make a comment about the presumption of your post.

Every single year hundreds of the phylogenic holes are filled. Ten years ago there were thousands less links and more empty spots than there are now.

I have found 100% no need to attribute the holes to anything other than the fact that we as humans have yet to fill them in.

The phylogenic tree is somewhere around 90+% completely.

So for any theories to arise to explain these holes other than the fact that we haven't found all the fossils we need yet are completely absurd.

It's just an absurd thought. It's like having to look around an entire room for microscopic parts to a puzzle, and continuing to find one after another, and at some point stopping to say - I have a theory why there is holes, because some pieces are mizzing - when it's obvious that at your current rate of filling it in their is a distinctly short period of time until the puzzle is complete.

See what I mean? Any such other claim is absurdity as absurd as creationism.

While you have a point, I think Greg Bear's idea actually involves the entire evolutionary process. IOW, he didn't just use it to explain why there are "gaps", but he used it to explain the very process of evolution altogether. In fact, IIRC, he even postulated the necessity of HERV for successful delivery of any human child (as though we had become dependent on these retroviruses, somewhere in our evolutionary past).

 

[Mentat]

Originally posted by iansmith
first, ERV are RNA virus that, once their genome is reverse transcribed into DNA, can integrate their genome into their host genome. There some old ERV viruse present in our genome. (http://www.nature.com/cgi-taf/DynaPage.taf?file=/ng/journal/v21/n3/full/ng0399_257.html).

The present of an integration can lead to many routes. The integration could cause an insertional mutation in a gene (i.e. the gene get knocked-out). The genomic integration could also be in "useless" (in relative term) part of the host genome creating no problem. These knock-outs, if beneficial, could explain some "gaps" in the fossil record.

I don't known how precise ERV can extract their genome out of their host. If some ERV are "slopy" (some viruses insert by accident host genes into their genome) and the ERV can cross species, genes could be transfert to one species to another. If this phenomen happens then it can explain some quantum leaps in term of evolution. The promoter and inhibitor of the gene should also be compatible with the new host. If it is not compatible, then the gene migth not express properly.

According to me, Greg Bear is forgetting that we only find some missing links and we have not identify all the species that have and are living.

I also think that the relation between stress factor and evolution is a joke. Experimentally we can isolate bacteria that are randomly resitant to antibiotic and no endogenous virus are found in their genome. Fruit fly can reproduce fast and generation can be randomly resistant to toxin.

ERV could explain some gaps but Greg bear example have flaws and are not the best.

Please see my response to CrystalStudios (above).

 

[iansmith]

Originally posted by Mentat
In fact, IIRC, he even postulated the necessity of HERV for successful delivery of any human child (as though we had become dependent on these retroviruses, somewhere in our evolutionary past).

Can you give us any example he used to support his claim.

 

[Mentat]

Originally posted by iansmith
Can you give us any example he used to support his claim.

Not really. Remember, this was a Science-Fiction novel, not a scientific text. Therefore, any "examples" would be ficticious occurances. However, the biologists in his novel seemed to put a lot of stock on the hypothesis of some other (ficticious) scientists: namely, the ERV were encoded into the developing baby (obviously) and helped it to fight off the immune system of the mother (which would, otherwise, kill the fetus). He gave a lot of cases in which the removal of ERV led to death of fetus, but they were all ficticious.

This is why I wanted to know about it's actual scientific relevance - all of his studies occur in a ficticious world, and are thus not really verified.

 

[iansmith]

Originally posted by Mentat
the ERV were encoded into the developing baby (obviously) and helped it to fight off the immune system of the mother (which would, otherwise, kill the fetus).

From what I remember in my immunolgy class, the baby does not have to figth the mother immune system. Instead, the mother's immune system is "not as alert as usual" due to change in hormone balance. For example, parasites infection that are kept in check during the "normal life" will reemerge during pregnancy. In some case the baby get "attack" by the immune system. The best example are the blue baby that are associated with the rhesus factor (http://freespace.virgin.net/angela.powell/rhesusfactor.htm).

So I don't think ERV have an effect on pregnancy but there some viruses that carry some homologous gene to human and sometimes these viruses can cause cancer and other genetic related disease.

In term of evolution, ERV could have participated to human evolution by transferring or deleting genes but usually the dormant ERV do not work properly and are "alive" (i.e. they do not spread to horizontally). ERV can be view as self-fish such as transposons and plasmids.

 

[Mentat]

Originally posted by iansmith
From what I remember in my immunolgy class, the baby does not have to figth the mother immune system. Instead, the mother's immune system is "not as alert as usual" due to change in hormone balance. For example, parasites infection that are kept in check during the "normal life" will reemerge during pregnancy. In some case the baby get "attack" by the immune system. The best example are the blue baby that are associated with the rhesus factor (http://freespace.virgin.net/angela.powell/rhesusfactor.htm).

So I don't think ERV have an effect on pregnancy but there some viruses that carry some homologous gene to human and sometimes these viruses can cause cancer and other genetic related disease.

In term of evolution, ERV could have participated to human evolution by transferring or deleting genes but usually the dormant ERV do not work properly and are "alive" (i.e. they do not spread to horizontally). ERV can be view as self-fish such as transposons and plasmids.

And yet, what if the virus (which is technically just "software" (information) with no "hardware") were to "remember" (by which I mean that it would collect data about previous experience) "beneficial" (by which I mean "...insuring survival") mutations of species? Obviously, the virus couldn't "remember" non-beneificial ones, because the ones that don't insure survival allow their species to become extinct, and thus that particular virus would die also.

I know it sounds kind of "new-age"-ish, and it isn't my main view or anything, but it sounded interesting; and I'd like to see what exactly is wrong with that idea.

 

[iansmith]

Originally posted by Mentat
And yet, what if the virus (which is technically just "software" (information) with no "hardware") were to "remember" (by which I mean that it would collect data about previous experience) "beneficial" (by which I mean "...insuring survival") mutations of species?

Beneficial/harmfull is a relative term in evolution. Beneficial/harmfull hundred or thousands of year does not mean beneficial today or in the future. Also the virus won't keep beneficial mutation in case of something happen. To me ERV acts as self-fish DNA like plasmid and transposon (http://www.geneed.com/glossary/t/index.html).

Plasmid and transposon can bring benefit to bacteria but there not a necesity and can also cause the death of the host. For example some transposon carry antibiotic resistant genes. These will help the bacteria at surviving but the transposon can jump out to another individual. The jump can be initated by great stress (i.e. the boat is sinking get out here). ERV could act in such a way therefore they maintain themself and are not driven to instinction but the host species is. The problem is that sometimes mutation occurs in the genes that respond to stress or that unable the transposon/ERV to "jump out" the chromosome (these gene are called transposase in transposons but I don't known about ERV). Therefore the transposon/ERV sink with the ship. If ERV can cross species and/or it as been in a species for many generation (therefore it has been pass to many individuals), it migth not be such a bit loss (if enough species/individuals survive).

Another example is that some plasmid can be maintain in host because it can encodes a stable toxin and an unstable antitoxin. When a baterium divide, one new bacterium migth have plasmid(s) where as the other one do not. Because the antitoxin is unstable, after a short time the toxin kill the host that do not posess a plasmid. Maybe ERV do have such a process, and gametes that do not possesses or have a mutation in the antitoxin gene migth be kill (this is an out of this world theory, we never know). I do not remember (I will have to read the papers again) that scientist were able to get those plasmid out the bacterial strain. Maybe it is where Greg Bear was coming from.