Gender

I have an important question that I have never heard being asked or answered.How did an asexual species evolve into a two-gendered species which had the capability to mate and (through extremely complex processes) bear offspring?

No one's going to tackle the origin of sexual reproduction?--Percy

Could it be that no evolutionists have an answer?

Oy! I'll set up to the challenge a bit late, albiet I only get ojnline every few days. ( I would have liked to respond sooner).
I posted on another forum somewhere that single cells have no problem reproducing asexually, do they? Well no, they dont... anyhow, if you can bear to take a look down evolution alley you would see that the first cells came together [ abridged version ] and formed complex cell bunches. the cell bunches then grouped together more and now we have the first multicellular animal. Each cell does it's thing, but they work together toward the common goal of feeding and reproduction. the cells then evolved to form specialized tasks, some would be for movement, others for sensing enemies, and other for digesting food in an effective way. to make a long story short the cells could have eventually just stayed grouped together and formed dogs and cats ( note I said eventually ). Well asexual reproduction wasnt quite the best way anymore, although cells in the human body are self-replicating, they stick to the specific tasks they are designed for. eye cells produce eye cells and ear cells produce ear cells. reproductive cells are the more efficient way to reproduce, they are specialized at storing and sending genetic code when required. Life starts anew. If humans could asexually reproduce themselves it would be a) messy, becuase humans arent designed for it and b) not productive, it would effectivley be a close the same age as you. reproduction lets life begin anew by the fusing of sperm and egg. Life begins young and with a fresh start. I hope that helped you some, it's alte and im tired, i worked all day, so please forgive me if I am way off base. -Kv

Given all the effort sexual organisms must put into reproduction (competition with others of their species, courting rituals, counter-adaptive qualities nonetheless advantageous because they attract mates, eg, bird's plumage, copulation, impossiblity of solo reproduction), why aren't sexual creatures at a disadvantage to asexual creatures? One might ask why, given all the disadvantages, the world isn't dominated by asexual organisms.If evolution is the correct theoretical framework then sexual reproduction should provide advantages, so what were the advantages that led to the evolution of the first sexual organisms? How might the first sexually diploid (two alleles for each gene, like us) organisms have arisen?--Percy

How many mutations do you think it would take at one time to allow sexual reproduction to begin happening?Besides, I don't think sexual reproduction is an advantage. Being able to reproduce asexually every day would be much more efficient in assuring survival of your own species.

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[This message has been edited by Cobra_snake, 01-20-2002]

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Originally posted by Cobra_snake:

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Besides, I don't think sexual reproduction is an advantage. Being able to reproduce asexually every day would be much more efficient in assuring survival of your own species.

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[This message has been edited by Cobra_snake, 01-20-2002]

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Sexual reproduction is most definately an advantage. Asexual reproduction relies on mutation to introduce changes in allele frequency, sexual reproduction does not.A hypothetical scenario:1/ A large mammals climate is cooling, it only reproduces asexually.Unless it can come up with some pretty convincing mutations in a couple of thousand years, it's joining the Dodo. A high rate of reproduction is irrelevent here, it just means that there will be frozen tundra full of dead animals adapted for a warm climate.2/ A large mammals climate is cooling, it reproduces sexually.As the climate cools & becomes a killer, individuals that have thicker fat layers, & or, thicker coats are able to "use" existing alleles of genes, passed on sexually, helped along by recombination. These "good" alleles are selected for by natural selection & become more common in the genotype of the species as a whole. The individuals which present the "very thin coat" allele die, individuals with "very heavy coat", or something inbetween stand a better chance of survival. Any helpful mutations would be a boon.Theres no guarantee that the sexually reproducing mammal will survive, plenty haven't, but it has an advantage in this scenario which the asexual reproducer lacks.Mark------------------
Occam's razor is not for shaving with.

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[This message has been edited by mark24, 01-20-2002]

Ok, in certain cases in today's world, sexual reproduction is very advantageous.But when the supposed first two-gendered species was formed, it most likely would not be considered an advantage.It's not like evolution has a mind of its own. Evolution doesn't sit down and think, "Well, if only the next species reproduced sexually, I would be able to make better creatures without using mutations!"

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Originally posted by Cobra_snake:

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But when the supposed first two-gendered species was formed, it most likely would not be considered an advantage.

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It's not like evolution has a mind of its own. Evolution doesn't sit down and think, "Well, if only the next species reproduced sexually, I would be able to make better creatures without using mutations!"

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Now that depends entirely on the environment. Single celled eukaryotes use sexual reproduction very successfully, thank you very much.
http://gened.emc.maricopa.edu/bio/bio181/BIOBK/BioBookDiversity_3.htmlEukaryotes are much larger than bacteria, & slower reproducing. There are going to be various situations where it may be better to be an asexual reproducer. If you like, nature has two coping mechanisms for change. 1/ Very fast asexual mutation dependant. 2/ Slow, sexual, but highly adaptive. Neither are completely better than the other, just different, they both work.Clearly, a larger multicellular organism that has a relatively longer life cycle is going to be at a great disadvantage when it comes to adaption if it relies solely on mutation. The large number of generations to get a range of positive mutations, leaves it at a disadvantage in a fast changing environment.Compare that to a bacteria (prokaryotic) that has a life cycle of 20-30 minutes. Much more chance of mutation, but no gene flow between individuals. FYI, mammalian (eukaryotic) mitosis cycle is about 12 hours ( http://esg-www.mit.edu:8001/esgbio/cb/cell_cycle.html )So, in summary, the longer the life cycle of an organism (don't confuse that with the mammalian mitotic cell cycle) the more suited it would be to sexual reproduction. Note, this is a rule of thumb, there are asexually reproducing multicellular organisms, the coelenterate Hydra, for example.Mark------------------
Occam's razor is not for shaving with.

Allright, fine. But I still see no evidence that sexually reproducing organisms can evolve from asexually reproducing organisms. Does ANY scientist have a logical theory?

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Originally posted by Cobra_snake:
Allright, fine. But I still see no evidence that sexually reproducing organisms can evolve from asexually reproducing organisms. Does ANY scientist have a logical theory?

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There are quite a few. One of the more common is that it evolved as a defense against parasites. Do a google search for Evolution of Sexual Reproduction. You will come up with numerous articles that discuss various scenarios. I don't believe that we have the complete answer to this question, though. Scientists are still working on this and important discoveries still need to be made.One of the better articles from the web is here: http://biomed.brown.edu/Courses/BIO48/19.Evol.of.Sex.HTMLSLD

It seemed the article mostly argued that there are advantages to sexual reproduction.I think you have to take a step back and look at the big picture. It is really quite ridiculous under current scientific knowledge to assume that (by chance) sexual reproduction would evolve. I don't see why one should suspect we will find new scientific knowledge in the near future that would allow for such impossibility.

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Originally posted by Cobra_snake:
I have an important question that I have never heard being asked or answered.

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How did an asexual species evolve into a two-gendered species which had the capability to mate and (through extremely complex processes) bear offspring?

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Try this site. You should fully read lectures 4, 5, and 6 (just click on the appropriate title). This Purdue University advanced bio course gives a pretty good overview of the issue. Enjoy

i think another environment adaptive mutuation for an asexual species would be quicker and more plausable than dozens of mutations with two sets of fairly different organs grown, let alone still being compatable. that one one adaptive mutation would breed like crazy and become much more numerous. the two-gendered species would still have to go through dozens of generations to get to being two-gendered and then it would still have to adapt. i dont think that anything up and mutates but adapting is natural for everything based on natural selection.anyway my names Noel Olson and yes im in the same village with my friends cobra_snake and nightfall60, we debate quite a bit. Im 16 and i play the bass guitar and soccer, i suck at both :-). i am also a creationist and a lutheran.------------------
"Overspecialize and you breed in weakness" -"Major" Motoko Kusanagi

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[This message has been edited by KingPenguin, 02-04-2002]

[b] [QUOTE]How many mutations do you think it would take at one time to allow sexual reproduction to begin happening?[/b][/QUOTE]Please clarify what you mean by "mutations...at one time".