...Something for you biologists to take a look at.

reply to scilosopher

What I took offense to in your post was your assertion that I was using my "experience," by which I guess that you mean my education, as a criteria for accepting my misconceptions (Your quote: "Everyone has misconceptions including me, please don't put forward your experience as a criteria for accepting yours."). Sounds like an attack to me. You also suggest that I not correct misinterpretations of evolutionary biology. Well, that was my intention all along, as I stated in my first post. I pointed out that there were misconceptions, that I could correct, but I would not do so unsolicited. I there fore thought that you either didn't read my post, or that you misunderstood it. I can think of no third alternative.

Lack of selective pressures or loss of selective pressures from environment or species interaction can lead to loss of gene function (loss of selective constraint on a gene will allow it to freely mutate). Examples are pseudogenes and some genes of the MHC. This loss of function is evolution. I can think of no examples where the following happens:

Your quote:
"To be clear, even elimination of selection for a certain trait alters the selective pressures on a species and therefore is effectively a selective pressure of its own (ie [sic] one could argue that removing a constraint could speed spread of a closely linked, but improved version of a gene. Essentially an effective pressure for the new and improved version)."

If you have examples of this (real ones, i.e. published) please pass them on.


Fitness is a relative term. Simply, it is the amount of one's genetic composition passed on to the next generation relative to the rest of the population. In most eukaryotes, this means reproduction, but there are exceptions (e.g. inclusive fitness).

I didn't attack you or question your intelligence, but as I stated, you either didn't read my first post or didn't understand what I meant.

 

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Oops

I hope that I did not start something bad here with all the arguing. I just love science and especially evolution and I like to here views on that.

Also, I have picked the Bows in March Madness!! Lets go Terps!!

 

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reply to terpsrule

Nah, you didn't start anything.

 

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ok then

Well I just like to talk...as you can tell. I am interested in learning more about the evolutionary processes. I just bought Darwin's book about it and want to read that soon.

 

reply to terpsrule: books

There's lots of great books out there. You know the Gould ones, which are great for non-specialists (and specialists, I read and re-read them all the time).

Also;

The Structure of Biological Science, Rosenberg
and
The Growth of Biological Thought, Mayr.

Best

 

paulsamuel

Our biosphere isn't changing that much.

If the definition of our biosphere is the part of the earth and its atmosphere in which living organisms exist or that is capable of supporting life, then I'll have to disagree. And so would others...

http://astrobiology.arc.nasa.gov/roadmap/objectives/o14_ecosystem_response.html

http://earthobservatory.nasa.gov/Newsroom/MediaResources/Changing_Global_Land.pdf

http://terra.nasa.gov/FactSheets/LandSurface/

A doubling of the air's CO2 content could well double agricultural production in many areas of the world by merely eliminating the adverse effects of but one air pollutant, i.e., ozone. Then, consider the fact that by the mid-point of the current century, we will likely face a food production crisis of unimaginable proportions...

The biosphere will continue to exist, but not as we know it; for most of its wild diversity of life will have been extinguished by mankind's mad rush to appropriate ever more land and water to grow the food required to feed itself

http://www.co2science.org/edit/v4_edit/v4n43edit.htm

 

Thanks

I appreciate the titles of the books. I am going to track them down and read them. Still want to read Darwin first and then get the other ones.

 

Oh goodness Terps, the 'Origen' is very dry and confusing. (Sheesh, Charlie goes on and on and on about pigeons)

I recommend reading 'Darwin's Ghost' by Steve Jones as a companion.

PaulSamuel: If you don't mind, what is the University of Hawaii like, biology department wise? I'm rather interested in genetics and microbiology especially, and I will probably go to the U of Michigan....but I'm still toying with different universitys.

Thanks.

 

Ok

Xev...what do you do? Are you heading into grad school at Univ of Mich?

 

Paul welcome to SciForums. Many members of this forum are very interested in the mechanisms of evolution. Member backgrounds vary widely which makes assuming knowledge or lack of knowledge a problem.

“I am a biologist and my expertise is in conservation and evolutionary genetics. There appears to be some confusion here about evolutionary theory, molecular clocks and scientific theory. Instead of posting unsolicited responses to misconceptions that I've read here, I'll just offer explanations in regards to evolutionary theory to whoever has questions. Ask away if you wish.”

This hamster believes you meant this as a generous offering. By not clarifying what posts contained the “confusion” and “misconceptions” the impression left is that all the posts were lacking. The only evidence provided was the authority of your degree.

This hamster, whose area of expertise is not biology, noticed this apparent rudeness. Scilosopher is very well versed in evolutionary biology. (This hamster has greatly appreciated Scilosopher’s postings on biology and evolution on this forum.) This hamster believes Scilosopher’s posts to you were a suggestion that you accord other posters the respect you would give a peer, i.e. don’t assume they are wrong. If they are wrong, explain your reasoning. Then everyone learns.

This hamster hopes to learn from both Paul and Scilosopher.

 

Here’s part of a discussion on aging that seems relevant to the topic of selection occurring in modern humanity.

“Julia Moravcsik wrote:

Mitochondria age as a person gets older. And yet the mitochondria that we had in our original ova are in the same direct line as our mother's mitochondria (and her mitochondria are in the same direct line as our grandmother's, etc.). It is basically like having mitochondria from the same, very old, organism (who happens to get very small (ova-sized) and then very big (human-sized). So why are the mitochondria of a young person "younger" than the mitochondria of an old person.

Aubrey de Grey replied:

Well, a one-phrase answer is "selection of the fittest": same as one's ova themselves must be no older then one's mother's ova were at the same age. Somatic cells (everything except ova and sperm and the cells that they come from) can age, because they don't lead to cells in one's progeny; hence, the constituents of those cells (such as mitochondria) can age too. Mechanistically, there are various tricks that the body uses to select the healthiest ova (which, among other things, means the ova with the healthiest mitochondria), including atresia, quiescence of ova until ovulation, and clever stuff in oogenesis to make sure that if an ovum is unhealthy then it's very unhealthy (so won't be fertilised).”

The hurdles an egg must pass from fertilization to birth is a selection process that weeds out some harmful mutations.

 

Paul,
The Hamster summed up my intent well. I just don't like "expertism" in general where somone puts themselves forward as holding the correct view on a given topic. I didn't mean to question the usefulness of your insights, but more the manner in which you presented your role. I agree that you didn't force your views on the thread, but I'm still just not a big fan of that kind of situation. I didn't intend to offend.

Nobody understands evolution that much is clear. Any evolutionary theory accepted or not will therefore have some misconceptions (at least in terms of missing pieces and how they alter the picture) buried within it. Including the views I hold. The fact that I said the same held true for me, makes me wonder why you considered it an attack. Especially since I said please.

Rather than discussing the details of our misunderstanding, please accept my apology (I'm sorry) and let's discuss some ideas. I look forward to hearing your perspectives. I'm much more versed in genetics, developmental, and molecular biology than evolutionaray theory, but any study of biology is greatly enriched by considering evolutionary aspects and I have certainly thought about them a lot. I'm sure my views may be crosswise at odds with certain evolutionary theories because of my mechanistic view of the system in question.

I might not have explained it well, but I believe I read something by Chip Aquadro that suggested hitch-hiking and related effects exist on closely linked genes (especially in regions of low recombination). I quickly browsed the abstracts in pubmed, but couldn't remember which one. There were statistics that supported him in the assertion as well if I'm remembering correctly (I read it over a year ago). I think its reasonable to expect that such effects could exist and significantly alter selective pressure on nieghboring genes both positively and negatively.

I would put forward that humans are more sensitive to natural selection than other organisms as by controlling our environment extensively (especially in medical/nutritional fixes to genetic defects), we alter selection which can feed into more modifications to our environment (ie increased dependence on medecine and research into fixes). We are essentially exposing ourselves to amplified natural selection. Allowing certain genotypes that could never have existed before is clearly imposing selection not buffering from it.

As we are increasing the proportion of some portion of the populace with an otherwise negative trait we are making certain individuals more fit and thereby selecting for the trait. If fitness and thereby natural selection is simply the differential transimission of certain genes or genotypes then we can't buffer ourselves from natural selection w/o explicitly attempting to maintain a specific genetic composition.

If I make any comment you find unclear or imprecise let me know. I will try and clarify, but generally there is a limitation to how much one wants to type and polish the wording of statements in a forum intended mainly for fun. I find that if one can state the difficulty seen with a brief idea/statement it is much more efficient. Often interesting details pop up, whereas a complicated precise statement requires a more complicated and precise response and can lead to an energetic barrier to interactive discussion.

Imahamster,
Interesting, the same considerations go for the germline in general (which is handled more by selection of progeny - and maybe zygotes in general). It makes me think about the maintenance of organization and how selection in some way seems to do work (in a thermodynamics/statistical mechanics sense) on a population. I'm having a hard time figuring out the flows of energy and where to draw the system boundaries as far as what exactly is doing work on what. Maxwell's demon comes to mind - all he did was to select.

 

Terpsrule:

Gracious, no. I'm 18, much too young for grad school. I've been going to a small community college for the last two years, and it's around time to transfer to a university and start on my.....well, I really don't know what.....

I shall spend the summer trying to accumulate money and figure out just what I want. So, I'm more interested in general information about, well, any school with good biology programs and department.

Any information would be appreciated....but I don't want to hyjack this thread. Thanks.

 

biologist

Paul welcome to Sciforums:

I am not a biologist. This is an interesting thread. I read this here and there, and then search for basic information, so maybe I will understand the essential of the thread. More doubts...I read it again. I am learning ...everyday.

Paul/Scilo/Hamster/Q: please continue sending information.

 

reply to Q

Thanks for your post. I guess I misunderstood your original post. I didn't mean to imply that the biosphere is static, that is obviously not true. What I meant to say is that the vagaries of the environment have not changed much in the last 50,000 years (since humans have been around).

For example, a quote from one of the links that you posted, "Yet, scientists cannot say what, if any, long-term impacts these changes will have on global climate systems."

This is what I was talking about. I am under the impression that large long-term changes in the global climate have not been documented since humans have been around. Of course this is hard to test. They've been using core samples in the Antarctic ice sheets to determine ancient climates.

I concur that deforestation, loss of biodiversity and large influxes of CO2 from the use of fossil fuels are affecting local environments, but it is hard to determine if these will have long-term global climate effects.

However, even short-term localized environmental changes will affect evolution.

My contention for human evolution is that, at least in technological human populations, natural selection is SOMEWHAT suspended. What do humans die from that would prevent their passing of genes to the next generation? Disease, but you have to subtract the selective pressures of diseases that manifest themselves after reproductive years.

Let's try to think of, and name other selective factors.

Best

 

Reply to terpsrule and Xev

Terpsrule, Origin is a hard read, but well worth it. It's amazing how correct many of his insights were, even though nothing was known of genetics at the time.

Xev, I love living in Hawaii. Best place I've ever lived. It will be hard to leave, but job opportunites for me are limited. The genetics department is good. In fact, Rebecca Cann, one of the originators of the "Original Eve" hypothesis of human evolution (The search for Eve. Science. 1992 Apr 3;256(5053):79.) is here. I know one prof. in micro, Ned Ruby, who's pretty famous (symbiosis of Vibrio in squid) but don't know much else.

Good Luck

 

Reply to Hamster

You stated

"This hamster believes you meant this as a generous offering."

You are right, and thank you.

Then you said,

"Scilosopher is very well versed in evolutionary biology."

I never said he wasn't.

And,

"This hamster believes Scilosopher’s posts to you were a suggestion that you accord other posters the respect you would give a peer, i.e. don’t assume they are wrong. If they are wrong, explain your reasoning. Then everyone learns."

I never accorded anyone with disrespect and never made any assumptions about them. I do believe that unsolicited interventions are rude, so I won't do them. I've only responded to questions and/or statements made directly to me.

Best

 

Reply to scilosopher

Ok, apology accepted. Just a couple clarifying points that may have led to our misunderstanding. You said,

"Any evolutionary theory accepted or not will therefore have some misconceptions (at least in terms of missing pieces and how they alter the picture) buried within it."

I was not talking about evolutionary theories that are (or were) controversial or could be wrong. I was talking about those posts that were unfamiliar with the theory or theories, so misinterpreted them in their posts. I listed some of those in a prior post. To attack a theory that one thinks is wrong is good for science. But to attack a theory because one has misunderstood what the theory was, or was unfamiliar with the theory or concepts behind it, then that's wrong, and fruitless. I am not denigrating those who are unfamiliar with the theories (one can't know everything), which is why I offered clarification on any of those unfamiliar theories. Also, because I know a theory and can explain it, doesn't mean that I am saying that it's true. All I'm saying is that that is the theory. And, I like theories (scientific ones, that is) that are at odds with accepted theories. It was only 50 years or so ago that plate tectonics was scoffed at.

Gene hitch-hiking is well documented. If you use "hitch-hiking" in PubMed search engine (this is the link for those who are interested <http://www.ncbi.nlm.nih.gov/>) you'll come up with a bunch of refs. Hitch-hiking is a type of linkage disequilibrium but a loss of selective pressure would not prevent a loss of genetic function in a hitch-hiking gene. What can happen is a "bad gene" (i.e. one that has negative selection on it) can be maintained in a population if it's tightly linked to a "good gene" (one under positive selection). Is this what you mean? (Anyone with questions on this topic, I'll be glad to try and answer them.)

When you say,

"I would put forward that humans are more sensitive to natural selection than other organisms as by controlling our environment extensively (especially in medical/nutritional fixes to genetic defects), we alter selection which can feed into more modifications to our environment (ie increased dependence on medecine and research into fixes). We are essentially exposing ourselves to amplified natural selection. Allowing certain genotypes that could never have existed before is clearly imposing selection not buffering from it."

we are talking at cross purposes but, I think saying the same thing. In humans (at least those in a technologically advanced society), virtually all humans survive to pass on their genes to the next generation. To me that means selection is relaxed (all survive, no selection). I think you're saying the same thing but you're calling it amplified selection. If this is true, we're arguing semantics, which I won't do.


You say,

"As we are increasing the proportion of some portion of the populace with an otherwise negative trait we are making certain individuals more fit and thereby selecting for the trait."

We are not actively selecting for that trait. That would require us to breed for that allele at the expense of the other. I do agree however that the proportion of that allele increases in the population and we are increasing the fitness of that individual.

Then you say,

"If fitness and thereby natural selection is simply the differential transimission of certain genes or genotypes then we can't buffer ourselves from natural selection w/o explicitly attempting to maintain a specific genetic composition."

Fitness is not the same as natural selection. Natural selection will maintain genetic composition (some genes have been driven to monomorphism through natural selection). We buffer ourselves from natural selection by lessening negative selection on some genes. Again, we may be arguing semantics.

Best,

 

This hamster’s take on Scilosopher’s point is that mutation “A” might have been disadvantageous without access to modern technology. Hence gene combinations including “A” might be disadvantageous. With technology, “A” in association with other genes is now a viable possibility. The range of viable gene combinations has been extended by technology.

Human technology has not stopped selection. It has only shifted the dominant selection forces. Removing one constraint allows others to dominate. Selection still occurs. (Parent survival is no longer a dominant selection factor in the US. Number of children is a significant factor. This hamster believes this is more selection of family culture rather than genes.)

This hamster believes that most human genetic selection occurs before birth. The selective competition among millions of eggs and sperm is intense. Gametes having only half the genetic material should further increase the selection pressure. Only after survival as a single fertilized egg does further selection at the multi-cellular level occur. Selection as gamete, selection as zygote, selection as embryo, selection as fetus, and finally selection as adult. Significant selection has occurred before a baby is born. To date most attention has been placed on selection after birth. This may be because the tools and science needed to study earlier phases has not existed.

 

Schools

Xev,

I can tell you right now that the UNiv of Maryland is a great school to go to. One thing, you are close to Washington DC and Baltimore, where there are lots of gov't type of jobs and you would be near of the biggest biotech centers in the country, besides California and Boston. IF you want more info email me at terpsrule1@lycos.com.

This thread is getting very good. Looks like we are addressing the issues well and I am enjoying them alot. Paul, can you email the titles of those books you were talking about? Thanks.