[rustbreeches]

My science vocabulary failed me right around cockroaches, but by golly, I am really liking this thread!

[mvp]

I'd like to add a little to what MVP has said. I'm getting my masters in molecular biology but my thesis is about evolutionary genomics. Not an expert by any stretch but I am interested in this stuff.

Someone asked about why species become more complex and not simpler. I would use a mathematical argument for this. There is a physical law that says everything tends towards entropy (chaos) but you can also think of entropy as just more information. It's like when you die your body decays it goes towards entropy. I would contend (right word?)that this is also part of the reason, if you think about genes and how they evolve, for the evolution of more complex species.

What it really boils down to (and no one is going to like this answer, especially people who believe in god or a higher purpose) is what is best for our genes. Essentially we are just hosts that our genes have made to best replicate themselves. Or to put it more eloquently I'll steel from my PI "life is what the genome surrounds itself with to survive". And this comes down again to math, because if something can replicate itself and something else can't, than the thing that will be around longer is the thing that can replicate itself. It almost seem, in that sense that life is inevitable, given enough time and material.

Someone else asked if only cockroaches and stubbens around be around after a nuclear holocaust. That is incorrect. Nematodes will be around I am sure of it. Nematodes (round worms--not just the kind you find in your horse, many are soil dwellers) are the most abundant multiorganism on the planet. I personally think they are the ultimate survival machine. You can starve them and they simply go into a stasis of a sort and can extend their life span by 3X or there abouts. You can freeze them in liquid nitrogen. You can even bleach them for a good 5 minutes and their eggs will survive. The only thing they don't like is dry heat but I'm sure given, that they make up 80% of the ocean floor they would have no trouble surviving a holocaust.

Someone else asked about why parasites kill their hosts. MVP already answered this but I just wanted to add to his answer. I will put on my population genetics hat and pretend to know what I'm talking about. ^_^ When talking about disease and I wouldn't be surprised if this applies to parasites as well, when you have a large host population you will find that a disease can afford to be much more virulent because there is always another host. With a smaller population the disease can't afford to be as severe. I probably did not explain that very well but hopefully you get the idea.

So... we'll have bugs, fugly saddles and worms after the nuclear holocaust. Super great. I'm not stayin'.

The population genetics stuff (see above) was put into forms that biologists in all fields could understand during the "Evolutionary Synthesis"-- roughly 1937-1953. IMO, it has become *the* modern restatement of Darwin's idea.

Because that math represents natural selection as a force, we get in the habit of talking about selection that way (again). Because the math also represents "evolution" in terms of alleles becoming more or less common in a population, we are invited to think about genes (properly: alleles) as competing for passage to the next generation.

Shiaway is correct in talking about virus' having "strategies" that work in larger and smaller host populations or genes that make organisms do this and that.

But beware the metaphors! Selection doesn't pluck single allele out of organisms and judge it. It kills or preserves the whole shebang-- that's lots of alleles, their interactions (maybe some responsive genes, maybe some epigenetic things). And selection might also be favoring some quality of the species. Yeah, some allele in some individual is going along for the ride from generation to generation. But it would be very, very tough to say "this allele is responsible for the species-wide property of, say, polymorphic coloring."

[mvp]

if men and women both belong to the same species, why are women so much higher evolved?

Meh, see above. There is real risk--of bad politics and unprovable science-- in talking about "higher and lower" with things evolutionary.

Don't believe me? How about the fact that the AIDS virus will kill any of us. It's small. It's not "alive" by common definitions of life. It won't come out and fight like a man. It's dirt simple.

Funny thing about men and women, and evolutionary theory. Some can't decide what or who does the selecting. In many theories of sexual selection, the women are the arbiters of reproduction at the end.

And then, really, all sexually-reproducing species need to do is be good enough to get it on with each other. Men can be heinous. Women can be heinous. Check out the child-ed couples on Jerry Springer and try to tell me that natural selection has high standards.

[mvp]

Also to MVP,
I wish evolutionary biologists wouldn't ignore introns the way they do. But I guess until more research shows their importance in the evolution of a gene and of the genome, they will continued to be mostly ignored.

Me, too. They should care about frame shifts. They should care about the amazing and unpredicted weirdness of DNA that repeats often. They should care about how we decided what was "genetic" and what was "epigenetic". They should have thought about different classes of genes a long time ago. Regulatory and structural genes didn't need to be such a recent distinction. They should hurry up and try to establish the evolutionary origins (dates and phylogenetic branching points) for old, conserved genes.

Since I just sit in the easy chair of the historian, I'll just take all of 20th-century biology to task for picking an evolutionary theory before they had more than a "meh...works good enough" theory of inheritance and development.

[CR Gorge Girl]

Finally! We get to the genetic definition of evolution...And we are into the first half of the 20th-century, folks.



A primer for the rest of yas, first:

We credit Gregor Mendel with supplying a "particulate theory of inheritance" that will work with natural selection. By 1909, these stable units transmitted between generations were named "genes."

An allele is one form of a gene. There can be two or more of these. They are part of the "classical theory of the gene"-- the one you learned. The "allele" talk still works, but genes-- yes, they are DNA, yes they are on chromosomes-- are now being redefined with respect to bits of morphology. No 1:1 correlation any more as Mendel ASSumed in order to get his (1865) experiments off the ground.

This "redefinition of the gene" going on now is especially true and important for evolutionists BECAUSE genetic theories of evolution treat the relationship between mutations to genes (an allele changing from one form to another) and the culling effects of natural selection.

More history: During the 1920s and 1930s, three math-heads, British statistician, R. A. Fisher, American physiological geneticist (dude who studies genes' expression during development), Sewall Wright, and J. B. S. Haldane (a jack-of-all-trades promoter of genetic theory and research) established Theoretical Population Genetics.

The goal of Theoretical Population Genetics was a phat one: To mathematically represent the process of evolution, and then to write equations that would tell you what would happen in different scenarios involving rates of mutation and intensity of selection.

Most of all, Fisher, Haldane and Wright wanted to show that Darwinian selection could work: The goal was to demonstrate that very little selection pressure (selection doesn't kill all of the organisms holding a given allele) and low mutation rate as is found in nature (new forms of a gene don't pop up often) would nevertheless produce directional and sustained change. This would kick all non-Darwinian theories to the curb.

Back to the question:

So "change in allele frequency" becomes the sign of evolution in this math and talk. Change in allele frequency means "The proportion of individuals in a population holding one allele as opposed to another." Presumably, selection was the force that created that proportion because genetic mutation is random with respect to selection pressure.

Because genes mutate in "all directions"-- toward the one that selection will preserve in a population over time and also toward the "bad" allele, you can see that selection will be more effective in a large population over time and small (or inbred) populations are SOL.

Big populations (and those with the right breeding structure) "hold" lots of variation-- lots of the alleles not currently favored. They can tolerate change in selection pressure.

Little or inbred populations are SOL: They *can't* respond to selection pressure because mutation rates are low. In other words, if a mutation normally occurs, say, once per every 10,000 generations, the population with just 1,000 individuals in it will have to wait (with the wrong allele) longer than will, say, a population with 100,000 members.

It gets more complex than if you consider genes' relationship to one another during development and therefore in their relationship to selection. But you get the basic mathematical system.

So!

1) Malaria is a famous example in which a key trait for survival has a single gene as its cause and just two alleles involved, IIRC. The heterozygous condition (one of each allele in individuals) is favored. It's not that these folks don't get malaria, it's that only some of the red blood cells will sickle in low oxygen environments for those individuals possessing both alleles. Given the prevalence of malaria in Africa (everywhere and for a very long time), no one will avoid it. But better to suffer with malaria than die from it before reproductive age. Thus, the allele that is deleterious in it's homozygous form gets preserved in the population.

In Europe, on the other hand, we can assume that the mutation did not show up. If it did there would be no benefit there to either the homozygous or heterozygous condition. Thus, the same allele would be lost (though slowly) in that population.

I'm not sure I have this malaria stuff right. I am sure I have the basic population genetics right. Take what you like....

2) Polydactyly in inbred populations. Whether it is caused by one gene or a suite of them traveling together on a small section of a chromosome, it's a math problem: Should that feature show up, it's original owners allowed to reproduce AND the population is small/inbred, the feature will stay.

3) Rates of speciation. A lot of handwaving here, folks. It's very, very hard to get a genetic description of a natural population or a species. Don't buy the hype too easily.

The hype-- particularly about wild species of Drosophila was sold to you by Theodosius Dobzhansky (a truly great scientist who worked with Wright on this stuff for 40 years), and Ernst Mayr. Mayr was another great intensely interested in developing a theory of speciation. The man did not read the math, FYI. We are now in the second half of the 20th century.

How fast does one species become another? Umm... if we are speaking in genetic terms, I'll have to insist that it's hard to measure. If we look at other ideas and data (Cichlid fish in Lake Victoria in Africa) we are looking at speciation rates that are much faster. The lakes themselves are only 12,000 years old. The number of species (and are they species?) is huge. But most people think it's hard to pin a "how many years" number for speciation.

Well, since the fish never come into contact with each other naturally, therefore never interbreed, they are separate species. Eastern and Western meadowlarks are almost identical, but since they don't recognize each others mating calls, they never interbreed, and therefore, are separate species.

and lol, you're pretty much saying the same things as my genetics prof, the textbook lays it out all pretty, but really it's not. Mendel got extremely lucky that the traits he chose to study were located on different chromosomes, and weren't linked to any other--no epistasis, no polygenic inheritance.

[mvp]

...and Volvos
..and Keith Richards

I'm loving this thread.

'K, post-human extinction we'll still have:

Cockroaches
Stubben Seigfried saddles
Nematodes
Volvos
Keith Richards... who will be lonely and really horny... and if he is lucky, the founding male of the next human species.

Have a nice day.

[mvp]

Well, since the fish never come into contact with each other naturally, therefore never interbreed, they are separate species. Eastern and Western meadowlarks are almost identical, but since they don't recognize each others mating calls, they never interbreed, and therefore, are separate species.

and lol, you're pretty much saying the same things as my genetics prof, the textbook lays it out all pretty, but really it's not. Mendel got extremely lucky that the traits he chose to study were located on different chromosomes, and weren't linked to any other--no epistasis, no polygenic inheritance.

Then you know that there are many, many species definitions out there.

I think Mendel chose the traits he did because they were on separate chromosomes and obvious. That's how you reliably get independent assortment.

On to the trick question, then: How do evolutionists know when selection is choosing an allele versus a bunch of genes linked in development versus a section of chromosome? I think it's an enormous problem built into Sewall Wright's fitness surfaces/adaptive landscape. Those are some incredibly influential diagrams in modern evolutionary biology. They have been assigned several different meanings...and few realize it.

[fargaloo]

Fun thread - my PhD is in evolutionary biology, but I have kind of drifted into community ecology of late....

One thing I'd like to add is that modern humans are experiencing very weak levels of natural selection as there is almost no correlation between genetic fitness (who survives and contributes alleles to the next generation) and genotype. Natural selection may kick in if we experience some kind of catastrophe that will lead to the collapse of modern medicine and technologies, but till then we are getting a free ride.

I agree - introns will be where it's at for the next while.... and all the rest of the "junk" DNA!

Here is a cool article on introns for anyone interested: http://www.sciencedaily.com/releases...1129112329.htm

[mvp]

Fun thread - my PhD is in evolutionary biology, but I have kind of drifted into community ecology of late....

One thing I'd like to add is that modern humans are experiencing very weak levels of natural selection as there is almost no correlation between genetic fitness (who survives and contributes alleles to the next generation) and genotype. Natural selection may kick in if we experience some kind of catastrophe that will lead to the collapse of modern medicine and technologies, but till then we are getting a free ride.

I agree - introns will be where it's at for the next while.... and all the rest of the "junk" DNA!

Ooh. Community ecology. So are you a fan of Niche Construction Theory? I can't decide if it says anything new or not.

And on weak selection for us: Are you saying that the correlation between single alleles and our whole genotype is limited? I'd expect that to be true for most alleles in most species most of the time.

Or do you mean a weak correlation between genetic fitness and phenotype....and those features "visible" to selection but not really killing anyone off?

[alterhorse]

Are there any predictable trends about evolution that might be used to form a computer model that might simulate a statistical probability of how people may change, and what they will become like in the distant future?

In other words can evolutionary science be use to predict future changes in living creatures?

Leave the environmental factors of weather, vegetation, and fauna exactly as they are now if it helps to simplify the modeling.

[fargaloo]

Yes, very true - I am talking about the correlation between fitness and phenotype. Selection on single alleles is pretty low, as you point out (thank goodness as they often prove to be useful down the road.... as species experiencing drift discover to their peril!)

I am not a huge fan of NCT - not that I don't acknowledge that it is true, but I think it's old wine in new bottles...it probably helps in modeling to explicitly build in feedback loops but I'm not a modeler these days

[Bluey]

Fun thread - my PhD is in evolutionary biology, but I have kind of drifted into community ecology of late....

One thing I'd like to add is that modern humans are experiencing very weak levels of natural selection as there is almost no correlation between genetic fitness (who survives and contributes alleles to the next generation) and genotype. Natural selection may kick in if we experience some kind of catastrophe that will lead to the collapse of modern medicine and technologies, but till then we are getting a free ride.

I agree - introns will be where it's at for the next while.... and all the rest of the "junk" DNA!

Here is a cool article on introns for anyone interested: http://www.sciencedaily.com/releases...1129112329.htm

I got a free ride.
Born right after WWII, I had pneumonia as a two year old, was very sick in the hospital and was one of the first in the general population to get that new miracle medicine, penicillin.

Sometimes, you get lucky and heck, that counts also in evolution.

[Ponytoes]

What if the Hokey Pokey is really what it's all about?

[Ponytoes]

Its a Jimmy Buffett song..

[mvp]

Are there any predictable trends about evolution that might be used to form a computer model that might simulate a statistical probability of how people may change, and what they will become like in the distant future?

In other words can evolutionary science be use to predict future changes in living creatures?

Leave the environmental factors of weather, vegetation, and fauna exactly as they are now if it helps to simplify the modeling.

Nope. No computer simulations. But a weird, fanciful picture book with a bunch of imagined options.

And yes, some biologists do try to predict changes in morphological form. It's fun and theoretical.

The best forms of this involve using "morphospace"-- and it works only for very limited kinds of features (shapes of shells, sometimes proportional ratios in dimensions of parts like skulls or bones). I think some people do it with plant shape.

First they need to do this developmentally-- talking about how genes (and the rest) produce the shapes they do. Then figuring in environment? I think you could do that for very well understood systems.

[mvp]

Yes, very true - I am talking about the correlation between fitness and phenotype. Selection on single alleles is pretty low, as you point out (thank goodness as they often prove to be useful down the road.... as species experiencing drift discover to their peril!)

I am not a huge fan of NCT - not that I don't acknowledge that it is true, but I think it's old wine in new bottles...it probably helps in modeling to explicitly build in feedback loops but I'm not a modeler these days

On Niche Construction Theory:

FYI: Mainly promoted by a very nice, old skool English guy, F. (?) John Odling-Smee since 2003 or so. He points out that organisms shape their environment, changing selection pressures for future generations and others. Think of beavers building dams.

Ecologists might have to care because while they usual think of "keystone species" or "trophic levels," these environmental engineers might really be the determiners of conditions.

Why do evolutionists have to care? Isn't community-engineering just one more element of "the environment" and selection pressure? I don't get it.

[mvp]

I got a free ride.
Born right after WWII, I had pneumonia as a two year old, was very sick in the hospital and was one of the first in the general population to get that new miracle medicine, penicillin.

Sometimes, you get lucky and heck, that counts also in evolution.

You did *not* get lucky. There is no luck in evolution. There are only changing selection pressures.

You were part of a species that invents cool stuff like penicillin and gives it to little kids. If you personally did "get lucky" it was by being born in the time and place that you were.

And so, my friends, there are some legitimate reasons to think of some of the big, collective good kinds of things we produce as "adaptive."

[Blugal]

Someone else on this thread brought up the idea that because we are doing so well as a species (at least, from a "taking over resources, reproducing, and edging out others" perspective), we also have greater numbers from which we can pluck great scientists, thinkers, etc. And from those, we may be able to come up with solutions to scarce resources/overpopulation problems.

I had not thought about it that way. I guess I had thought about it the way the movie Idiocracy portrays it (although I realize this is simplistic): tons of reproduction by the masses, very little reproduction by the highly educated/wealthy. Increased fighting over scarce resources.

What do you think?

[Tom King]

Where did all the stuff come from that created the big bang?

It was condensed from the last cycle. Matter and energy are different states of the same stuff. After it all turns to energy, it passes the equilibrium point, and comes back together as matter, and when gravity pulls it all back together to the breaking point, it explodes and starts all over again. Our universe is probably not the only one.

[alterhorse]

It was condensed from the last cycle. Matter and energy are different states of the same stuff. After it all turns to energy, it passes the equilibrium point, and comes back together as matter, and when gravity pulls it all back together to the breaking point, it explodes and starts all over again. Our universe is probably not the only one.

I like those sorts of mind boggling ideas.

Makes me envision multiple universes existing in a multiverse, and then multiple multiverses existing in a water drop clinging to the side of a stone next to a meandering woodland stream.