Freethought & Rationalism Archive

l-bow · 07-02-2003, 03:16 AM

Hello,

I was browsing another non-evolution related forum when a christian started talking about evolution and why its not possible. One of his arguments was that it is impossible for sexual reproduction to have evolved, since all the components needed to be there all at once.

If you want to look at the actual post, here is the link.

http://forum.teamxbox.com/showthread...on#post2504434

l-bow · 07-02-2003, 06:16 AM

Actual quote:

For instance, my theory on evolution and creation is so simple that it irks me to no end to have people argue with it and yet never come up with an explanation:

If a living being were to evolve a sexual reproductive system when it didn't have one before, it would have to pass thru a "partially formed" stage during its evolution. You can't go from 0% to 100% without passing thru 50%. (Well, and 40% and 60% and 30% and 70%...) And yet, a partially formed sexual reproduction system would be eliminated thru evolution, not passed on. For me, this is a smoking gun as to why evolution could never have been responsible for the origin of the species or jumps from one species to the next. A sexual reproduction system could only exist if it was placed into a creature's design, fully formed. It really is that simple.

If you figure that it had to happen with both sexes, in the same species, in the same geographical location, in the exact time span, with no outside interference, and these two mutations were compatible and viable? You believe THAT and you can't believe in a supreme being? How freakin' stupid is it possible to be? There seem to be new records set daily in this place.

**EDIT** a clarification of my sexual reproduction point above... if you look at the giraffe and know from the fossil record that they originally had long necks, you must understand that the very earliest giraffes had the propensity for long and short necks. The ones with the "longer" necks found food when the ones with the "shorter" necks couldn't. Now all there are are long necked giraffes. Basically, they ELIMINATED the short necked genes from the giraffes, similar to the way one would refine gold or silver. A little of everything that is not gold or silver is burned/melted off until all you have left is the precious metal. What makes a giraffe was part of a compound found in the original creature, and while still a compound the giraffe is now closer to an "element" than a compound. They did not ADD long necked genes just like you wouldn't add gold to a compound to make it gold. You'd take a compound with gold in it and remove everything that isn't gold. Evolution does not have the power to create, only to eliminate.

If you follow that same thread of logic, then all creatures must have had the information for sexual reproduction in their genes from the very beginning, and just evolved OUT their asexual system of reproduction. But it's pretty clear that paramecium have no information for sexual reproduction anywhere in their coding. So again, the theory is flawed on multiple points. Yet peopl ewould rather grasp onto this errant way of thinking, rather than acknowledge a Creator that they would then have to answer to.

l-bow · 07-02-2003, 06:56 AM

Stumped? I read in talk.origins that the evolution of sex is one the difficult problems of evolution. Don't asexual bacterias have plasmid transfer?

Non-praying Mantis · 07-02-2003, 07:11 AM

I don't want to reply to the whole ignorant post, but this part I know for a fact is wrong:

Quote:

Originally posted by l-bow
...But it's pretty clear that paramecium have no information for sexual reproduction anywhere in their coding. ...

Paramecia, and other ciliates have multiple nuclei. The main nucleus (the control center of the cell - where the DNA is stored that is transcribed to make RNA which is used to make proteins) has several copies of DNA (that condition is called polyploid). In addition to the main nucleus, there are several smaller nuclei which have only two copies of DNA (this condition is called diploid - similar to the condition of all of our own cells).

These diploid nuclei are used in a sexual process called conjugation. During conjugation, two paramecia merge together, combine their "micronuclei" (the small diploid ones), and form a new organism with all of the DNA of micronuclei making a new "macronucleus" (the large polyploid one).

Paramecia can also divide normally in asexual mitosis to make exact copies of themselves.

NPM

Wounded King · 07-02-2003, 08:08 AM

There are a number of other examples of bacteria which can reproduce both asexually and sexually, both have diferent benefits of course.

As long as the bacteria can also produce asexually there is no reason why a limited form of sexual reproduction could not propagate, as long as it conferred some advantage. One advantage of sexual reproduction is to help populations to overcome clonal interference which is a common problem in assexually reproducing bacterial populations.

Dr.GH · 07-02-2003, 09:17 AM

This sexual reproduction question is not difficult. For openers, there are the bacterial lateral genetic transfers. Then we note that primitive plants algae, ferns etc. propagate asexually, and also self fertilize seed. Primitive flowering plants are wind pollinated, and produce no nectar.

In terms of unicellular critters, most can reproduce simply by division, but some can form multinucleated forms which then exchange genes. Even multicellular forms such as hydra can reproduce sexually or by budding. Most mollusks are hermaphrodites, many are sperm and egg broadcasters. No special apparatus needed. No boy discovers his penis, but dies alone.

There are living examples of reproductive strategies that range from asexual to sexual that are "reachable" from one end to the other by small variation.

Simple.

Non-praying Mantis · 07-02-2003, 11:15 AM

Quote:

Originally posted by Wounded King
There are a number of other examples of bacteria which can reproduce both asexually and sexually, both have diferent benefits of course.

I haven't heard of any bacteria that can reproduce sexually. If you are refering to conjugation in bacteria and lateral gene transfer, then that is not part of what is normally called "sexual reproduction." IIRC, sexual reproduction usually entails meiosis at some point. Bacteria can't do meiosis.

However, it does accomplish some of the same goals as sexual reproduction - such as spreading and mixing of genes.

NPM

Nic Tamzek · 07-02-2003, 02:45 PM

We had a thread on this a year or two ago wherein I posted some refs on this topic.

l-bow, if you actually want some answers, you can start with:

Quote:

Heredity. 2002 Feb;88(2):125-41.

Origins of the machinery of recombination and sex.

Cavalier-Smith T.

Department of Zoology, University of Oxford, South Parks Road, Oxford, OX1 3PS, UK. tom.cavalier-smith@zoo.ox.ac.uk

Mutation plays the primary role in evolution that Weismann mistakenly attributed to sex. Homologous recombination, as in sex, is important for population genetics--shuffling of minor variants, but relatively insignificant for large-scale evolution. Major evolutionary innovations depend much more on illegitimate recombination, which makes novel genes by gene duplication and by gene chimaerisation--essentially mutational forces. The machinery of recombination and sex evolved in two distinct bouts of quantum evolution separated by nearly 3 Gy of stasis; I discuss their nature and causes. The dominant selective force in the evolution of recombination and sex has been selection for replicational fidelity and viability; without the recombination machinery, accurate reproduction, stasis, resistance to radical deleterious evolutionary change and preservation of evolutionary innovations would be impossible. Recombination proteins betray in their phylogeny and domain structure a key role for gene duplication and chimaerisation in their own origin. They arose about 3.8 Gy ago to enable faithful replication and segregation of the first circular DNA genomes in precellular ancestors of Gram-negative eubacteria. Then they were recruited and modified by selfish genetic parasites (viruses; transposons) to help them spread from host to host. Bacteria differ fundamentally from eukaryotes in that gene transfer between cells, whether incidental to their absorptive feeding on DNA and virus infection or directly by plasmids, involves only genomic fragments. This was radically changed by the neomuran revolution about 850 million years ago when a posibacterium evolved into the thermophilic cenancestor of eukaryotes and archaebacteria (jointly called neomurans), radically modifying or substituting its DNA-handling enzymes (those responsible for transcription as well as for replication, repair and recombination) as a coadaptive consequence of the origin of core histones to stabilise its chromosome. Substitution of glycoprotein for peptidoglycan walls in the neomuran ancestor and the evolution of an endoskeleton and endomembrane system in eukaryotes alone required the origin of nuclei, mitosis and novel cell cycle controls and enabled them to evolve cell fusion and thereby the combination of whole genomes from different cells. Meiosis evolved because of resulting selection for periodic ploidy reduction, with incidental consequences for intrapopulation genetic exchange. Little modification was needed to recombination enzymes or to the ancient bacterial catalysts of homology search by spontaneous base pairing to mediate chromosome pairing. The key innovation was the origin of meiotic cohesins delaying centromere splitting to allow two successive divisions before reversion to vegetative growth and replication, necessarily yielding two-step meiosis. Also significant was the evolution of synaptonemal complexes to stabilise bivalents and of monopolins to orient sister centromeres to one spindle pole. The primary significance of sex was not to promote evolutionary change but to limit it by facilitating ploidy cycles to balance the conflicting selective forces acting on rapidly growing phagotrophic protozoa and starved dormant cysts subject to radiation and other damage.

Unless you are able to rebut the literature at this level you are not even making a serious challenge...

Wounded King · 07-02-2003, 03:01 PM

Hi NPM,

It wasn't actually a bacteria I was thinking of, I was just being sloppy, that sentence was a complete work of fiction. I recently read a paper about facultive sexual reproduction in Chlamydomonas reinhardtii which, as I temporarily seem to hace managed to forget, certainly isn't a bacteria.

This is mainly due to inexcusable laxity on my part, sorry. I was in a unicellular = bacteria mode of thinking, sloppy and stupid.

TTFN,

WK

Normus · 07-03-2003, 09:18 PM

Along similiar lines, i dont quite understand why even if in theory evolution is possible, why a new species would gain or lose a set of chromosome pairs making it impossible for it to mate with any other species that came from a common species.

07-02-2003, 03:16 AM	#1
l-bow Regular Member Join Date: Jul 2001 Location: Hawaii Posts: 215	Evolution of sexual reproduction not possible? Hello, I was browsing another non-evolution related forum when a christian started talking about evolution and why its not possible. One of his arguments was that it is impossible for sexual reproduction to have evolved, since all the components needed to be there all at once. If you want to look at the actual post, here is the link. http://forum.teamxbox.com/showthread...on#post2504434

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07-02-2003, 06:16 AM	#2
l-bow Regular Member Join Date: Jul 2001 Location: Hawaii Posts: 215	Actual quote: For instance, my theory on evolution and creation is so simple that it irks me to no end to have people argue with it and yet never come up with an explanation: If a living being were to evolve a sexual reproductive system when it didn't have one before, it would have to pass thru a "partially formed" stage during its evolution. You can't go from 0% to 100% without passing thru 50%. (Well, and 40% and 60% and 30% and 70%...) And yet, a partially formed sexual reproduction system would be eliminated thru evolution, not passed on. For me, this is a smoking gun as to why evolution could never have been responsible for the origin of the species or jumps from one species to the next. A sexual reproduction system could only exist if it was placed into a creature's design, fully formed. It really is that simple. If you figure that it had to happen with both sexes, in the same species, in the same geographical location, in the exact time span, with no outside interference, and these two mutations were compatible and viable? You believe THAT and you can't believe in a supreme being? How freakin' stupid is it possible to be? There seem to be new records set daily in this place. EDIT a clarification of my sexual reproduction point above... if you look at the giraffe and know from the fossil record that they originally had long necks, you must understand that the very earliest giraffes had the propensity for long and short necks. The ones with the "longer" necks found food when the ones with the "shorter" necks couldn't. Now all there are are long necked giraffes. Basically, they ELIMINATED the short necked genes from the giraffes, similar to the way one would refine gold or silver. A little of everything that is not gold or silver is burned/melted off until all you have left is the precious metal. What makes a giraffe was part of a compound found in the original creature, and while still a compound the giraffe is now closer to an "element" than a compound. They did not ADD long necked genes just like you wouldn't add gold to a compound to make it gold. You'd take a compound with gold in it and remove everything that isn't gold. Evolution does not have the power to create, only to eliminate. If you follow that same thread of logic, then all creatures must have had the information for sexual reproduction in their genes from the very beginning, and just evolved OUT their asexual system of reproduction. But it's pretty clear that paramecium have no information for sexual reproduction anywhere in their coding. So again, the theory is flawed on multiple points. Yet peopl ewould rather grasp onto this errant way of thinking, rather than acknowledge a Creator that they would then have to answer to.

07-02-2003, 06:56 AM	#3
l-bow Regular Member Join Date: Jul 2001 Location: Hawaii Posts: 215	Stumped? I read in talk.origins that the evolution of sex is one the difficult problems of evolution. Don't asexual bacterias have plasmid transfer?

07-02-2003, 08:08 AM	#5
Wounded King Veteran Member Join Date: Mar 2003 Location: Edinburgh Posts: 1,211	There are a number of other examples of bacteria which can reproduce both asexually and sexually, both have diferent benefits of course. As long as the bacteria can also produce asexually there is no reason why a limited form of sexual reproduction could not propagate, as long as it conferred some advantage. One advantage of sexual reproduction is to help populations to overcome clonal interference which is a common problem in assexually reproducing bacterial populations.

07-02-2003, 09:17 AM	#6
Dr.GH Veteran Member Join Date: Jul 2001 Location: Dana Point, Ca, USA Posts: 2,115	This sexual reproduction question is not difficult. For openers, there are the bacterial lateral genetic transfers. Then we note that primitive plants algae, ferns etc. propagate asexually, and also self fertilize seed. Primitive flowering plants are wind pollinated, and produce no nectar. In terms of unicellular critters, most can reproduce simply by division, but some can form multinucleated forms which then exchange genes. Even multicellular forms such as hydra can reproduce sexually or by budding. Most mollusks are hermaphrodites, many are sperm and egg broadcasters. No special apparatus needed. No boy discovers his penis, but dies alone. There are living examples of reproductive strategies that range from asexual to sexual that are "reachable" from one end to the other by small variation. Simple.

07-02-2003, 03:01 PM	#9
Wounded King Veteran Member Join Date: Mar 2003 Location: Edinburgh Posts: 1,211	Hi NPM, It wasn't actually a bacteria I was thinking of, I was just being sloppy, that sentence was a complete work of fiction. I recently read a paper about facultive sexual reproduction in Chlamydomonas reinhardtii which, as I temporarily seem to hace managed to forget, certainly isn't a bacteria. This is mainly due to inexcusable laxity on my part, sorry. I was in a unicellular = bacteria mode of thinking, sloppy and stupid. TTFN, WK

07-03-2003, 09:18 PM	#10
Normus Junior Member Join Date: Apr 2003 Location: U.S. Posts: 32	Along similiar lines, i dont quite understand why even if in theory evolution is possible, why a new species would gain or lose a set of chromosome pairs making it impossible for it to mate with any other species that came from a common species.

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