Thanks for all the hard work Seattleguy. Will keep muh eyes peeled for the next installment of your series! (I remember that 7,000 years bit as well)
w.
Evidence for evolution, Installment 1: Endogenous retroviral sequences
by seattleniceguy 38 Replies latest jw friends
-
-
Cygnus
Hey SNG... you seem like........ a nice guy. Have your fun trying to prove evolution into your brain and heart. But remember there's a LOT more to life than spending all of yours trying to figure out where it came from. I spent a good four years learning, studying, debating evolution, and now all I care about is being a good person.
-
seattleniceguy
Hello Cygnus,
Have your fun trying to prove evolution into your brain and heart. But remember there's a LOT more to life than spending all of yours trying to figure out where it came from. I spent a good four years learning, studying, debating evolution, and now all I care about is being a good person.
I already feel that evolution is very well substantiated. But I found that when asked to give supporting evidence I was sometimes at a loss for specific examples. This, combined with the fact that I am fascinated by biology anyway - as indeed I am by all fields of science - made me decide to study up a bit more. I'm more motivated to keep at it when I describe what I'm learning to others, and I thought others here might enjoy it.
So no worries. I have nothing to prove. It's just fun to learn. :-)
SNG
-
Midget-Sasquatch
SNG
Just finished reading the entire thread....Perfect point to start off with IMHO.
Your explanation was one of the clearest versions I read, and your followup illustration with the brochure within the text (to the_classicist) was brilliant.
Looking forward to all the installments in your series.
-
Robdar
Interesting thread.
Question: Could death be a retrovirus?
I know it's probably a stupid question.......
Robyn
-
AlmostAtheist
Another question, SNG. The retroviral infection would have occurred in only one member of the species, true? Then it would have spread through the population via reproduction. Today, do all members of the species carry it? If so, why? Wouldn't there be lineages that carried it and others that don't?
Very interesting thread!
Dave
-
Abaddon
Classisist
Personally, I don't know if evolution is true or not, no one can really "prove it" beyond a reasonable doubt, yet.
It's fine for you not to know.
However, your question makes me ask two questions before I or others can really help.
First of all, what do you mean by "evolution"?
Second, what do you mean by "prove it".
The reason why I ask questions is you could mean:
Personally, I don't know if <there is a fossil record showing how organisms arose and in time were replaced by other organisms typically of greater complexity>, no one can really <show me an animal evolving> beyond a reasonable doubt, yet.
Or you could mean;
Personally, I don't know if <we know how evolution happened>, no one can really <prove any particular theory about the mechanism of evolution> beyond a reasonable doubt, yet.
Evolution is a fact - "dem bones dem bones dem dry bones" and a theory - "the lesser-spotted daffodil evolved due to a chance mutation of the blahdy-blahdy-blah-blah".
Proof is likewise double in meaning; "prove to me by showing me it happen from start to finish how a caldera is formed" and "demonstrate a theory explaining how calderas are formed".
Evolution certainly happened. There's a mass of evidence. HOW it happened etc., is open to debate.
Proving a very lengthy process by 'showing' someone is going to be impossible in most instances of evolutionary (or indeed geological) time. However, that doesn't mean that a theory that is supported by the evidence is wrong, it just means we can't watch creatures evolve or say with absolute conviction how it happens. Normally.
However, two species giving rise to a second species with which it is not fertile but which is in itself fertile has been observed both in the lab and in the wild.
To watch a randomly variated/mutated individual with 5% greater chance of producng and rearing children until they in turn breed (than a non-mutated member of the species), slowly 'use' this selection advantage to increase the number of organisms in the population with that mutation until they first dominate the population and the old population dwindles away is a difficult thing in the wild. This is called speciation.
It takes place in several circumstances; in the above a better surviving version replaces the old.
In others random variation will allow some organisms to better exploit resources; they will tend to breed with like organisms. There are a few lakes in Africa that are filled with fish that have evoloved to fill every biogical niche as the ancestor stock were the only fish to be in the lake when it was formed by geological processes, A single species has diversified into non-interbreeding very dimorphous seperate species. In this instance one species becomes more than one species with or without the parent species survivng.
In still others geographical isolation will mean at some point genetic drift through random variation or pooling of certain characteristics by selection (or both) will mean the geographically isolated species can not interbreed with the parent species any more. This is like the first instance except the parent species doesn't die out but is removed from contact with the new species (although it might die out in the original habitat in the course of time)
Now, if is hard to watch these happening, yes. But there are still islands with many types of finch all apparently descended from one type. Those African lakes with their many species from one. Many cave systems also provide examples of speciation caused by isolation.
So, speciation or 'micro' evolution by a variety of mechanisms HAS been proved, if one regards proof as 'a level of certainty it would be illogical or peverse to dispute".
The 'bigger' jumps between species are impossible to observe due to the time scale involved; this 'macro' evolution is however well attested to in the fossil record; when small steps between species can happen so easily and commonly, all you need to do is stack lot of these changes together.
However, you're far better off reading and digesting this web site than listening to me witter on...
... although feel free to ask questions as there's several people on the board who love this shit.
As SNG has already pointed out, the similarities being refered to are not in terms of common structures or amino acid production; can I take it that that is answered to your satifstaction?
-
seattleniceguy
Dave,
The retroviral infection would have occurred in only one member of the species, true? Then it would have spread through the population via reproduction. Today, do all members of the species carry it? If so, why? Wouldn't there be lineages that carried it and others that don't?
Awesome questions. I had been thinking about those as well. Disclaimer: The following is what I think is the answer, but I need to do more research.
Yes, the retroviral infection happens in a single member of the species. The infection occurs at a specific point in the creature's genome, on a specific chromosome. Recall that half of an offspring's gene's are contributed by the mother, and half by the father, so this infection will land at a particular spot in the offspring that will be either a male-contributed chromosome or a female-contributed chromosome. If the infection first occurred in a female, the infection would land in a spot in the offspring that is passed on only if the offspring is female. In other words, the infection would be passed through females only - a matriarchal succession of infection. (This is the part I need to double-check on. Perhaps those with more knowledge of genetics can help me here.)
As the pyramid of infection grows, soon all members of a society will have it, because it is a permanent infection that can never be "healed." However, a geographically or reproductively isolated group of the species would not have the infection.
Therefore, it is possible for two individuals to be related but not share the infection, BUT any two individuals that do share it are definitely related. We might consider it as an extremely specific disorder that runs only in your family. It would be possible for you to have a sibling that is spared from it, but if you meet some other random person that has it, they are definitely related to you.
It is possible that there will be members of a species that never receive the infection, but that would only be because of reproductive isolation, possibly because they are geographically separated from the infected group. And it is precisely this type of isolation that leads to evolutionary branches. So the two groups will eventually diverge. If they meet up again somehow before a divergence happens, then the infection will spread to the uninfected group.
Just to clarify, let's consider a scenario. Say we had a group of cats, all of whom share a base retroviral infection. We'll call that one Infection 1. One day, a hapless female gets her ovum infected with Infection 2. This ovum becomes a kitten who now carries both infections. If the kitten is a male, then Infection 2 is not passed on any further, because it is in a female-contributed location on the genome, which a male cat cannot contribute. But if the kitten is a female, then all of her offspring will have the infection. So the infection begins to spread.
However, part of this group lives in the Eastern US and half in the Wastern US, and no interbreeding happens because the kitties can't make it over the Rockies. Poor things just don't like the cold. In that case, Infection 2 would be limited to, say, the Western cats. So at this point in time, we have two groups: Infection 1 occurs in all members of the species, showing that they are all related. Infection 2 occurs in a sub-group of the species only, showing that this group is more closely related than the species in general.
If the groups remain separated, in time they will diverge and reproductive isolation will be strengthened so that even if they were to meet up, they would not interbreed. (A lion will not mate with a housecat.) The infections would, however, be a record of their varying degrees of relatedness.
To recap, the only thing I'm unsure about is whether a retroviral infection actually travels down a gender-specific line as I have guessed. But this is actually immaterial to the bulk of the discussion. For the retroviral infection to have significance in tagging related species, the only thing necessary is that it is passed on through reproduction.
SNG
-
seattleniceguy
Hello Rodbar,
Question: Could death be a retrovirus?
I know it's probably a stupid question.......
Retroviruses can clearly cause death (HIV is a common retrovirus) but I don't see how the two can be related in any other way than that.
SNG
-
Abaddon
I suppose the question of the likelihood of relatedness in organisms with a specific insert is directly related to the nature of the original retrovirus. If it was a very rare event, then relatedness would be near certain. If certain retroviruses did that as part of their particular life-cycle, then an entire population might be infected.
This would mean rather than just monkey #3456785432 with the insert, doing a Ben-Hur and being the sole ancestor, or whatever, you have maybe all of the ancestor population, which merilly reproduces away, all with the insert, but with the end result having the insert would not link you with monkey #3456785432.
Also, is the insert necessarily a precise correlation to the differentiation, or is it something which infected all members of an ancestor population shortly after differentiation (in evolutionary timescales)? Common chimp/man ancestor differentiates into two streams, and then a population gets whacked with a retrovirus? Which just happens to be around the same time as the correlation?
To what extent do retrovirus inserts take place within a species today? Is it possible to say, find linages with different inserts in a inter-fertile population? How often does it happen when observed now by science?
Are there even retroviruses that do infest an initial hosts germ cells as a matter of course, as I speculate?
Not all retroviruses would necessarily be harmful or symptomatic outside of the genetic realm.
Their 'goal', any organism's 'goal' is to reproduce. A 'wise' parasite does not kill its host, unless by doing so it ensures its reproduction.
Ebola, for example, is too deadly too quick. It burns itself out it spreads so fast. Short of mass infection in a major population centre or a variety evolving which is as deadly but takes three months to develop (bye-bye civilisation), it will never be very 'successful' as some epidemics have been. Unless it did that, even a major population centre would leave many communities infection free, worldwide, before they knew they had to lock down.
A virus doesn't have to be harmful.
Much to my surprise, the search string "benign Endogenous retro-viral retrovirus evolution" (normally if you get too specific you get nothing) gave lots of hits, like;
http://darwin.bio.uci.edu/~faculty/villarreal/new1/erv-placental.html
A genomic retrovirus: essential for placentals? In a proposal published in 1997, I raised the issue of endogenous retrovirus and proposed that these viruses are essential to the biology of Eutherians. Viviparous mammals confront an immunological dilemma in that mammals which have highly adaptive immune systems fail to recognise their own allogenic embryos (58). The relationship of mammalian mother to her fetus resembles that of a parasite and host in that the fetus 'parasite' must be able to suppress the immune response of the 'host' mother in order to survive. As viviparous mammals are also noteworthy for having genomes that are highly infected with endogenous retroviruses and as retroviruses are generally immunosuppressive, the possible participation of endogenous retroviruses in the immunosuppression by the embryo was then considered. In addition, it was considered if such endogenous viruses might be more broadly involved in the evolution of their host and the resulting host genome that now appear to have many derivatives (such retrotransposons and as LINE elements) of such genomic viruses. This grant application seeks support to do an experimental evaluation in a mouse model of the proposed involvement of endogenous retroviruses in the immunologically escape by the embryo in the mother. I argue that endogenous retrovirus is hence essential for the biology of non-egg laying placental mammals. This study could provide evidence of the biological function of endogenous retroviruses and also address the broader issues concerning the possible contribution of genomic virus to host genome evolution
Such a retrovirus of course WOULD be in all memebrs of descendants and would correlate with the differentiation event.
Lord only knows. I have some reading to do but can't be arsed at the moment...
;-)
Nice thread.