Biological evolution - prebiotic chemistry, biogenesis, evoluti

Palomar · 2003-10-14 11:32:19

Whoa, Cindy! I was only enjoying a little bit of intersexual 'warfare'.
To really get into that type of recreation, you have to assume males and females are all stereotypical. It was just a joke, that's all.
But the deteriorating Y-chromosome thing is supposed to be for real, though I don't know enough about genetics to express an opinion on it.

A Gift for Shaun

*No problem, Shaun.

I was hoping you were simply in a "jesting vein" (although some women can be the way you described, I know...I'm related to a few of those sort!).

Regarding the alleged deteriorating Y-chromosome story: Earlier this year a report was going around on U.S. television networks that true blondes will be "extinct" by 2200 or thereabouts...bred out of the gene pool. Turns out this "report" was bogus (thank goodness).

--Cindy

Bill White · 2003-10-14 13:12:04

But as I said earlyer, I think that we evolute now under Lamarckian mode rather than darwinian mode because we transmit acquired characters (in the form of information, not genes) to our offspring.

This reminds me of a cute story I once heard about passing information, customs and culture between human generations.

A young woman decided to cook a Sunday dinner for her family. Just before putting the roast in the oven, she sliced off a piece on both ends and set the pieces on an open space in the roasting pan.

"Why did you do that? her husband asked.

"I don't know, thats how my mother always did it."

Intrigued, later they both asked her mother why she cut the ends off of roasts before cooking. The woman's mother said, "You know, I really don't know, my mother always did that also."

More intrigued, all three of them went to see Granny and they asked why she cut off the ends of roasts before cooking.

Her anwer? "Oh my, do you really remember that?"

"You see our first apartment was very inexpensive and the oven was too small to hold an entire roast so I had to cut off the ends so it would fit. Tell me, why in the world would you remember my doing that?"

dickbill · 2003-10-14 15:19:58

Perhaps it works via activied genes from specific environmental input. These activated genes then have the opportunity to be transmitted into offspring, or, the offspring are more likely to exhibit these enviornmentaly-specific genes becuase they live in the same type of environment as their parents...

It is known that some genes are imprinted, being not expressed equally in male and female, but in general, I would say that it's the rule, rather than exeption, that genes expression depends on environmmental factors.
Take an example: production of melanine under high solar exposition to make a tan. Well, I don't know exactly the mecanism, but I would guess that some proteins in the skin, either damaged or activated by the sun ray, come to activate the melanine genes, possibly trough a cascade of genes. Now, there is also a feed back system, at least in white people, because the tan doesn't stay long if the insolation disapears.
This involves a lot of genetic switches, promotors, inhibitors, different forms of RNA produced from a single gene, but the network is tranmitted with the melanine gene OFF by default. We could as well imagine that white people would be born with the genetic switch to ON by default, due to a mutation, and have fully melanised or tanned babies, and that the tan would disapear in abscence of sun rays after a couple of weeks. Would that make a difference or an advantage ? I don't know, but make no mistake, here again, this is an example of speciation, not evolution. Tanned or not, human will still be human.

How much do we know about the formation of new gene squences due to environmental changes within a species? Very little I would guess. Yet I am willing to bet there is a mechanism that allows the environment to 'encode' our gene squences to be transmittable to offspring.

You bet well. Molecular biologists and geneticist now know a little bit about the mecanisms of Mutations . The term mutation is very general by the way, it designs anything that could change the genetic network. One mechanism that could allow modification of information is the "homologous recombination " system. Look how this mechanism could be trigger BY the environmment to launch an evolutionary adaptation:

1) First point, you know that different species have similar genes, that is not surprising since we have common ancestors, so we share common genes with mice, fishes etc. These mice or firshes genes are similar but not identical to our genes, their sequences are different. When two genes of identical sequence comes in contact, very often they undergo what we call an homologous recombination. These genes exchange part of their DNA sequence, which is equivalent to say that they exchange information. To be efficient that mechanism request that the sequence of the two genes must be identical on several thousands base pair of lenght.

2) In bacteria, foreign DNA can enter pretty easily, through phages or other vectors of DNA, like plasmids that bacterias use for quasi-sexual mating. Bacteria too share genes between strains or species and these genes are homologous then, whith a very similar sequence. But since these bacteria are so promiscuitous and that this DNA is so abundant, sometimes the DNA of one bacteria enters a bacteria of another strain or specie. Since the genes are homolgous, sometimes they are exchanged and a bacteria can acquire new information that way (like resistance to an antibiotic), but not much often as we could expect, why's that ? Its because one bacteria of a specie is able to recognize the DNA of other species using small differences in the DNA sequence of the Homologous genes. This inhibates the recombination and the host bacteria can refuse the incoming DNA when it comes from foreign species. This is dependant of specific proteins that inhibate or stimulate the recombination.

3) But now imagine an environmental change, a harsh stress for example. Suddenly the proteins that recognize the foreign DNA become less picky, and as a result foreign DNA can be integated more easily into an host of different specie. In short, the stress induces the bacteria to accept foreign genetic information. Other mechanism amplify that "stress induce evolution". The DNA repair mechanisms becomes less efficient, on purpose, so that mutations can accumulate freely in the bacteria submitted to that stress. The bacteria genetic content is now under heavy shuffling and explores all the possible ways to survive the stress, at a crazy rate.

The result is that a harsh change in the environment has induced a genetic change, as you suggested Clark.

Notice that it is not completely Darwinian. Darwin says that the mutations pre-exist, good or bad, at random, then the environmental change appears, then the fitest survive. Lamarck says that the organism adapts to the environment and transmit their adaptation. It's a mixture of both. The theory of evolution is best described by not excluing Lamarck IMO.

Shaun Barrett · 2003-10-17 01:34:28

Thanks for the gift, Cindy.
I was fascinated by 'Washington's rules of Civility and Decent Behaviour .. ', though I think it lost something in the translation in certain places!
The class-consciousness of the time is very apparent but in general, if we all tried to adhere to the majority of the rules, I'm sure it would be a more gracious world.

dickbill · 2003-10-27 14:49:25

Darwin: populations contain variants, some, by chance, are more or less fit to their environment, the fitest survive and transmit their genes. On the course of eons, the survival of the fitest create a step by step improvement in their adaptation to their environment, called "Evolution".
Best improvment in Darwin's Theory (in my opinion) : Gould punctuated equilibrium.

Lamarck: Populations contain individuals that adapt to their environment, for example some of the individuals develop
a certain skills or muscles that make them better adapted or successfull in their ecosystem. These acquired adaptations are hereditary tranmitted to their offspring, which in the course of eons generate better adapted individuals, which is the cause of evolution.
The theory was abandonned because the genetic transmission of acquired characters is false. However, in higher organisms such as mammals, skills and behaviour are learned and transmitted. Who could deny that the way lions hunt can make the difference between death or survival and would could deny that lions teach their offspring ?

So, I have always wonder why Lamarck's theory of transmitted characters has not been better reshaped and integrated with Darwin's theory to make a stronger Theory of Evolution. When evolutionists talk about Theory of Evolution, they mean Drawinism or neodarwinism, never Lamarckism or neolamarckism.

Sure, Lamarck was wrong, and his theory could not have been considered without a lot of modifications, but was Darwin's theory more accurate ?
Darwin never talked about genes and genetic mutations for example, that was added after by other people. Same for his step by step evolution. So why the theory of evolution stays so Darwinian and never even considered Lamarck ideas ?
My opinion: it was to keep the theory of evolution purely materialistic and away of any danger of becoming deterministic, because Larmarck's idea, even if not deterministic, allow the evoluting organisms to have a grasp on their destiny.

Under a Lamarckian mode of evolution, there is no predetermination, no big book of fate either, BUT, organisms create their own evolutionary path and work on their own fate (at least those organisms with enough consciousness or information treatment capabilities, in which I would include all mammals).

And as I said before, nothing forbid to consider dual mix mode of evolution, like my previous analogy with the mixed ionic/covalent nature of the chemical bond.

Preston · 2003-10-27 16:19:18

I think that "dual" theory of evolution is what we have, since the most basic statement of evolution is that "self-replicators self replicate" whether they be genes or memes (ideas/learned behavior patterns). The biological "Darwinian" evolution made brains, and the brains opened the door to meme evolution. And of course genes and memes are tied to each other, often or always, e.g., genes are more likely to self replicate if they spawn a brain which is eager to absorb the surrounding culture when it is young (since a locally common behavior pattern is interpreted as a locally successful behavior pattern).

dickbill · 2003-10-27 17:00:53

I think that "dual" theory of evolution is what we have, since the most basic statement of evolution is that "self-replicators self replicate" whether they be genes or memes (ideas/learned behavior patterns). The biological "Darwinian" evolution made brains, and the brains opened the door to meme evolution. And of course genes and memes are tied to each other, often or always, e.g., genes are more likely to self replicate if they spawn a brain which is eager to absorb the surrounding culture when it is young (since a locally common behavior pattern is interpreted as a locally successful behavior pattern).

Unfortunatly in evolution books, little place is given to lamarck. It's all about "Darwin's genial intuition" etc etc. As if Darwin created the whole theory of Evolution from A to Z alone from scratch. Come on, what about the Goeffroy-St Hilaire, Cuvier Lamarck ?

since the most basic statement of evolution is that "self-replicators self replicate"

That reminds me of what say the tenants of the Intelligent Design theory: they critic Darwin in joking his "survival of the fitest" by "survival of the surviviest".
I don't think that evolution can be reduce to self replicators that self replicate (even with some modification). With just that, I would expect speciation, not macroevolution.
Now, if the self replicator can also acquire some information in its lifetime (and become the fitest of Darwin that way), and transmit it to its offspring, that's different. But this is a Lamarckian concept. Darwin would say that the best self replicator is the best by chance, not by working or acquiring information.

The biological "Darwinian" evolution made brains, and the brains opened the door to meme evolution. And of course genes and memes are tied to each other, often or always, e.g., genes are more likely to self replicate if they spawn a brain which is eager to absorb the surrounding culture when it is young (since a locally common behavior pattern is interpreted as a locally successful behavior pattern).

Then, it is not the biological "Darwinian" evolution that made brains, it's the biological Darwinian AND Lamarckian evolution that made brains and in the case of brains I think it is more the Lamarckian evolution. But I agree with the concept of memes.

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#26 2003-10-14 11:32:19

Re: Biological evolution - prebiotic chemistry, biogenesis, evoluti

#27 2003-10-14 13:12:04

Re: Biological evolution - prebiotic chemistry, biogenesis, evoluti

#28 2003-10-14 15:19:58

Re: Biological evolution - prebiotic chemistry, biogenesis, evoluti

#29 2003-10-17 01:34:28

Re: Biological evolution - prebiotic chemistry, biogenesis, evoluti

#30 2003-10-27 14:49:25

Re: Biological evolution - prebiotic chemistry, biogenesis, evoluti

#31 2003-10-27 16:19:18

Re: Biological evolution - prebiotic chemistry, biogenesis, evoluti

#32 2003-10-27 17:00:53

Re: Biological evolution - prebiotic chemistry, biogenesis, evoluti

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