Sexual Dimorphism

[Sathanas]

" In fact all animal species have evolved from the stage where there were no distinct male and female, and the reproduction was asexual. Sexual drive was present even then – apparently because it serves an important biological purpose. E.g. strong sexual drive is found amongst species that have not yet achieved sexual dimorphism. There are either only females or a hermaphrodite being, but sex still takes place throughout the year --- unlike in male-female sex which is only when procreation is required.

Thus sexual drive precedes sexual dimorphism. These are clear evidences that nature chose sex as a means to reproduce by either diverting a small part of sexual urge (already present for same-sex) into male-female mating, or by creating an urge to reproduce. "

 

is this true ?

 

this is the thread http://www.sciforums.com/threads/heterosexuality-is-unnatural.50083/

 

 

???

[CharonY]

It does not make a lot of sense to me. Typically libido refers to the desire for sexual activity. In asexual reproduction you have, by definition, no sexual act. So how can there be any interpretation of sexual drive in this context? You would have to define cellular division as an sexual act then, which makes no sense on many layers (e.g.absence of sexual recombination). So no, it certainly follows a weird train of thought that are not in line with the usual definitions.

 

Also it weirdly reminds of some weird posts that were around here a while ago...

[Wolfhnd]

Exchange of genetic information is something that happens in asexual organism. Allopolyploidization is widespread.

 

Horizontal genome transfer as an asexual path to the formation of new species

 

http://www.nature.com/nature/journal/v511/n7508/abs/nature13291.html

 

Methods of Genetic Exchange in Bacteria

 

http://www.biology.ewu.edu/aHerr/Genetics/Bio310/Pages/ch16pges/ch16fs.html

 

The exchange of genetic material in bacteria is important part of the mechanism by which anti biotic resistant bacteria evolve.

 

Recent research indicates that resistance can even be transferred outside of hosts. This make containment of antibiotic resistant bacteria particularly troublesome.

 

 

Sexual dimorphism is usually restricted to discussing the differences between sexes not related to reproduction directly. The existence of sex on the other hand is usually explained by the "parliment of genes" seen in meiosis. The question of which came first diploidy or sex is of some interest.

 

Giardia: A Missing Link between Prokaryotes and Eukaryotes

 

"The diploid state can be greatly advantageous, and most highly evolved, complex organisms have adopted this arrangement. If a cell has only a single copy of genetic information, any alteration or mutation of that information could result in nonfunctional proteins, with dire and possibly lethal consequences for the cell. But if the cell has two sets of instructions and one of them becomes nonfunctional, the second set can serve as a backup, and may compensate for the loss of the first. Furthermore, if a segment of the first set undergoes a mutation that provides a new beneficial function, the other copy can still perform the original function. With only one set of instructions, the organism risks losing an existing function to gain a new one. Again, this could ultimately lead to the cell's demise. A diploid organism has the advantage of retaining the old while developing new, advantageous functions.

The putative haploidy of each of the Giardia nuclei is intriguing with respect to the organism's evolutionary importance. It is possible that a single haploid nucleus gave rise to a second identical nucleus, thus giving the entire organism the various advantages of the diploid state. Later in evolution, the two haploid nuclei could have fused to produce the sole diploid nucleus characteristic of most higher eukaryotes. This hypothetical scenario explains the transition of a haploid prokaryote to a diploid eukaryote. It also predicts that the higher eukaryotes that contain a single diploid nucleus are the evolutionary descendants of a binucleated eukaryote."

http://www2.nau.edu/~gaud/bio372/class/readings/giard.htm

The quoted post I believe is just a simplified version of a search for the true evolution of sex. As you can see it is an area of intense interest for biologist that is not easily covered here. In general though if you leave out the idea of sex drive, which unavoidably refers to a neurological process, the original statement has some validity. I like to think that these statement suffering from what I call the chicken and the egg fallacy. Life evolved to evolve so changes to the environment cannot be entirely separated from the way organism effect each other or the environment.

It is also important to note that "culture" can not be separated from development of the human brain. While we think of sexual attraction as a mix of physical and psychological factors there is a unbroken chain of evolution that goes back to asexual organism that predates even rudimentary consciousness. This is a hotly debated issue in so far as it is becoming popular amongst some biologist to say that "intelligence" is a property of simple organism. Once again we are faced with the chicken or the egg and the question of degree or kind. Do bacteria desire to exchange genetic information? I guess it depends on how far you want to stretch the degree versus kind argument.

Edited February 16, 2015 by Wolfhnd

[Wolfhnd]

I made a mistake earlier in this post that I apologize for when I select web references. I hope nobody got the impression I supported the views of the linked website. Google can be dangerous if you are careless.

[CharonY]

Horizontal gene transfer is independent of reproduction. Also it is maintained by specific uptake and recombination mechanisms (i.e. in the context of mobile genetic elements). It does have little to do with the question in OP.

 

The evolution and maintenance of sexual reproduction, however, is a an intriguing subject as it has to offset the two-fold cost of sexual reproduction. There are a few mechanism-oriented hypotheses that I find interesting, though I am not sure whether a consensus has been established yet.

[Wolfhnd]

Horizontal gene transfer is independent of reproduction. Also it is maintained by specific uptake and recombination mechanisms (i.e. in the context of mobile genetic elements). It does have little to do with the question in OP.

 

The evolution and maintenance of sexual reproduction, however, is a an intriguing subject as it has to offset the two-fold cost of sexual reproduction. There are a few mechanism-oriented hypotheses that I find interesting, though I am not sure whether a consensus has been established yet.

Thanks for the clarification that I'm not sure I included.

 

I was trying to be as open minded as possible about what was being discussed and what the question was without going into detail about the original posts.

 

I hope you can comment on the trend for some scientist to attribute "intelligence" to bacteria as my comments on horizontal gene flow was meant to imply some sort of evolutionary continuity. I assumed that the original post was fishing for a continuity that included early organism but that was just a guess. There is a lot of fairly speculative literature out there that could be misleading but is interesting.

[Sathanas]

It does not make a lot of sense to me. Typically libido refers to the desire for sexual activity. In asexual reproduction you have, by definition, no sexual act. So how can there be any interpretation of sexual drive in this context? You would have to define cellular division as an sexual act then, which makes no sense on many layers (e.g.absence of sexual recombination). So no, it certainly follows a weird train of thought that are not in line with the usual definitions.

 

Also it weirdly reminds of some weird posts that were around here a while ago...

I agree with you.

This thread was started by a certain person who claims sex-attractions being dominant and primary than opposite-sex attarctions. He claims procreation is distortion of "sexual drive". He claimed that men are in general attracted to other men, not to women ( this is the reason he claimed sexual dimorphism being secondary than "sexual" drive ). The same sex attractions can never be primary in terms of evolution as they cannot lead to reproduction. According to me opposite sex attractions are must, otherwise species cannot exist.

The case of same-sex attractions being more dominant than opposite-sex attractions, in sexual orgasnisms maybe true but the most important attractions are between opposite sex organism these lead to reproduction. While same-sex attraction may exist or not exist they are not as important as compared to opposite attractions. Thus opposite sex attractions are primary while all others are secondary.

The 'drive' he reffered cannot be sexual as sex leads to its most important function reproduction, but the organisms that indulge in this certain 'drive' may try to assert their dominance.

" In fact all animal species have evolved from the stage where there were no distinct male and female, and the reproduction was asexual. Sexual drive was present even then – apparently because it serves an important biological purpose. E.g. strong sexual drive is found amongst species that have not yet achieved sexual dimorphism. There are either only females or a hermaphrodite being, but sex still takes place throughout the year --- unlike in male-female sex which is only when procreation is required.

 

Thus sexual drive precedes sexual dimorphism. These are clear evidences that nature chose sex as a means to reproduce by either diverting a small part of sexual urge (already present for same-sex) into male-female mating, or by creating an urge to reproduce. "

 

If this is true then it would mean all the species have intelligence, that the same-sex attractions developed are not natural, they should be intentional. The phenomenon of same-sex attraction can also be defined as parasitic in nature i.e. the a single orgasnism for its survival depends on another orgasnism.

It does not make a lot of sense to me. Typically libido refers to the desire for sexual activity. In asexual reproduction you have, by definition, no sexual act. So how can there be any interpretation of sexual drive in this context? You would have to define cellular division as an sexual act then, which makes no sense on many layers (e.g.absence of sexual recombination). So no, it certainly follows a weird train of thought that are not in line with the usual definitions.

 

Also it weirdly reminds of some weird posts that were around here a while ago...

Can you point me those posts ?

[Wolfhnd]

This thread should have been called the origin of a sexual predisposition or similar. Sexual dimorphism is a phenotypic difference between males and females of the same species not sexual attraction.

[starlarvae]

On origins of gender dimorphism, see recent paper on origins of pregnancy at http://www.cell.com/cell-reports/fulltext/S2211-1247%2814%2901105-X . Comment from Brig Klyce at http://www.panspermia.org/whatsnew80.htm ::::

 

"Thousands of ancient genes simultaneously repurposed and re-regulated by invasive TEs? Such complex, coordinated steps must have relied on powerful genetic programming. It strains credulity to suggest that the programming was suddenly, incrementally composed by darwinian trial-and-error. The programming must have been available already."

In other words, this seems to be an amazing case of "pre-adaptation."

[CharonY]

Thanks for the clarification that I'm not sure I included.

 

I was trying to be as open minded as possible about what was being discussed and what the question was without going into detail about the original posts.

 

I hope you can comment on the trend for some scientist to attribute "intelligence" to bacteria as my comments on horizontal gene flow was meant to imply some sort of evolutionary continuity. I assumed that the original post was fishing for a continuity that included early organism but that was just a guess. There is a lot of fairly speculative literature out there that could be misleading but is interesting.

 

 

Could you elaborate on that? I am not sure what you mean.

 

 

Can you point me those posts ?

 

Unfortunately, no. It was a while back and it also followed a convoluted, strongly extrapolated reasoning that had little connection to actual data. I do not think the poster is around anymore.

 

On origins of gender dimorphism, see recent paper on origins of pregnancy at http://www.cell.com/cell-reports/fulltext/S2211-1247%2814%2901105-X . Comment from Brig Klyce at http://www.panspermia.org/whatsnew80.htm ::::

 

"Thousands of ancient genes simultaneously repurposed and re-regulated by invasive TEs? Such complex, coordinated steps must have relied on powerful genetic programming. It strains credulity to suggest that the programming was suddenly, incrementally composed by darwinian trial-and-error. The programming must have been available already."

 

In other words, this seems to be an amazing case of "pre-adaptation."

 

I do not know who Klyce actually is, but it seems like drivel to me. It is grossly overstating what the study found. Essentially they indicate that TEs may play a bigger role than currently known in creating new regulatory networks. Also he states "simultaneously" whereas the study obviously can only compare extant organisms. In fact, it shows that mammalian pregnancy required the gradual change (loss as well as well as gains) by comparing it to frogs, chicken, lizard and marsupial. Also why would he classify transposable elements as invasive? At various points they are quite endogeneous the the respective species and there is little doubt that they were heavily involved in shaping them.

Using this as basis and then making extrapolations. Seems like awfully bad science reporting (again).

[fiveworlds]

" In fact all animal species have evolved from the stage where there were no distinct male and female, and the reproduction was asexual. Sexual drive was present even then – apparently because it serves an important biological purpose. E.g. strong sexual drive is found amongst species that have not yet achieved sexual dimorphism. There are either only females or a hermaphrodite being, but sex still takes place throughout the year --- unlike in male-female sex which is only when procreation is required.

 

Thus sexual drive precedes sexual dimorphism. These are clear evidences that nature chose sex as a means to reproduce by either diverting a small part of sexual urge (already present for same-sex) into male-female mating, or by creating an urge to reproduce. "

 

is this true ?

 

 

It is doubtful to be true but male-female mating is actually reasonably weird in nature. But nature can be really odd flatworms for instance don't really have any specific male-female but instead have both which is really weird. There is also a small number of humans that are male and female

Edited February 18, 2015 by fiveworlds

[Sathanas]

The microscopic organisms exchange genetic material through contact.

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