How Did Sexual Organs Evolve in Mammals?

I am not trying to get cheap laughs on this one but I just wonder about a few things regarding the evolution of sex in mammals.

Firstly, how did the sperm evolve a protective mechanism (prostatic fluids etc..) against a place (the vagina) that it has never seen before- and develop an acrosome that helps to cut through the egg?

Secondly, how did the penis and vagina evolve after the requisite millions of years of evolution and selection? How did the organs develop a gradual mechanism that would give a quarter vagina a selective advantage?

For example why would a half penis be more selectively advantageous than a quarter penis?

I suppose I am looking for possible mechanisms because it is a complete puzzle to me.

What you just wrote is a good example to me why evolution did not happen to bring man from bacteria.

For creationists we were made by a creator. Can you imagine all the things that would have to go right for a male and female mammel to reproduce if it was left to evolution. There had to be a creator.

What does a half penis and a quarter penis mean, can a man have a 2 sized penis. Do you mean there is an average, or something.

[edit on 7/20/2007 by andy1033]

Here'a an article on evolutionary novelties and the evolution of the vagina. Guess it's relevant.

enjoy

Wagner & Lynch (2005): www.sendspace.com...

i'm not quite the expert on this, but i know one of the earliest stages was insemination in some form of worm through, i'm not making this up, penis fencing. whoever pierced the other one got to fertilize

Originally posted by andy1033
What you just wrote is a good example to me why evolution did not happen to bring man from bacteria.
For creationists we were made by a creator. Can you imagine all the things that would have to go right for a male and female mammel to reproduce if it was left to evolution. There had to be a creator.
[edit on 7/20/2007 by andy1033]

Really? so you think someone sat down and designed humans, and butterflies and trees and ants rather than evolution and natural selection?

Sorry but no one is that good.

I would imagine that a short "half" penis would work better than no penis. growing longer with evolution probably made it easier to get the semen to the ovum without it getting contaminated or destroyed by nature. Also, those with deeper vaginal openings probably could protect their received sperm easier thus increasing the chances of those with slightly longer penises or slightly deeper vagina (up to a point) would be more likely to reproduce and through time all we have are these huge macho logs dangling between our legs now and vaginas as opposed to some slimy gunk that traps the sperm until needed later like squid. echhhh. be glad we evolved the way we did.

Originally posted by melatonin
Here'a an article on evolutionary novelties and the evolution of the vagina. Guess it's relevant.

enjoy

Wagner & Lynch (2005): www.sendspace.com...

Melatonin - good to hear from you again. I have just returned from a short holiday and, although knackered, have scanned through the article on molecular evolution. It provides a brave and honest 'state of the molecular evolution' type of statement. They do state that they used a low number of samples but it is obvious that the Hox genes are like organiser genes that can have a major effect on the reproductive tract. However, in each case that the team examined therian organisms (mammals for the most part), they examined individual organisms.

Even if there are male equivalents of Hox, and I am sure some will be found, the question still remains. How are sperm adapted for a place that they have never visited? My inductive reasoning cries out God! and your inductive reasoning cries out Natural Selection. However, it is interesting that the paper mentioned selection of organ specific gene networks which is touching upon Endogenous Adaptive Mutagenesis...

I will read the article again when less tired but this is fascinating stuff because wholesale changes can be caused by the appearance of novel trancriptional effectors.

I've been perplexed by examples like this of complimentary parts in different stages of life or different sexes that work together great, but hard to imagine being evolved in tandem.

Other examples are the placenta and uterus in placental mammals, pouch in marsupials ready for barely developed babies, and many others.

Originally posted by djohnsto77
I've been perplexed by examples like this of complimentary parts in different stages of life or different sexes that work together great, but hard to imagine being evolved in tandem.

Other examples are the placenta and uterus in placental mammals, pouch in marsupials ready for barely developed babies, and many others.

This is it. I think that genetic novelties were envisaged to 'accelerate' change of an organ, which is fine. But the evolution in tandem was not touched upon. It is in the realms of pure speculation.

Two points I'd like to make:

1) Sexual reproduction has been around far longer than mammals, and is not a unique trait to us, and

2) There are organisms on the planet who have both sets of reproductive organs, as well as others who have the ability to change genders to meet reproductive "demand".

I would say that the two sets of organs evolved side by side in ancient prehistory. I'm not a biologist or geneticist, but that would be my take on it.

[edit on 25/7/2007 by Thousand]

Originally posted by Thousand
Two points I'd like to make:

1) Sexual reproduction has been around far longer than mammals, and is not a unique trait to us, and

I don't dispute that point or the existence of different types of sexual organ development. However, the Hox genes can have multiple effects on mammalian/therian sexual organs and I think that these regulatory genes could provide a key to 'accelerated' evolution by the types and numbers of genes that survive mutation events.

2) There are organisms on the planet who have both sets of reproductive organs, as well as others who have the ability to change genders to meet reproductive "demand".

This may be the clue that I was looking for. However, we are still talking about Natural Selection here. There would have to be a selective advantage at each step of a mutation - even in a controller/regulator gene otherwise the idea flops. If there is no selective advantage to a penis developing if the female reproductive organ is not fully developed then the feature will be selected out!

Originally posted by Chorlton

Originally posted by andy1033
What you just wrote is a good example to me why evolution did not happen to bring man from bacteria.
For creationists we were made by a creator. Can you imagine all the things that would have to go right for a male and female mammel to reproduce if it was left to evolution. There had to be a creator.
[edit on 7/20/2007 by andy1033]

Really? so you think someone sat down and designed humans, and butterflies and trees and ants rather than evolution and natural selection?

Sorry but no one is that good.

I do not claim to knwo the process. But i believe the universe is a computer program(even sciencetists are saying so know that we may be on someones computer). Dna is just a program isn't it. For me we where created, does not mean that evolution does not take place, but like many there is no way man came from bacteria.

That does not mean i do not understand where evolution comes from, i do. I just think there is a master plan behind it all.

2) There are organisms on the planet who have both sets of reproductive organs, as well as others who have the ability to change genders to meet reproductive "demand".

That in it self is not proof. We know there are different ways to reproduce, for me eventually man will go back to having one gender, through technology and evolution.

Ask yourself how can the reproductive process be so perfect(i know there sometimes are things wrong), and how males and females came into being. I suppose its the chicken and the egg.

By thousand

2) There are organisms on the planet who have both sets of reproductive organs, as well as others who have the ability to change genders to meet reproductive "demand".

By Andy1033

That in it self is not proof. We know there are different ways to reproduce, for me eventually man will go back to having one gender, through technology and evolution.

Ask yourself how can the reproductive process be so perfect(i know there sometimes are things wrong), and how males and females came into being. I suppose its the chicken and the egg.

As always, Andy, as always... However, I have read so much about evolution that I don't doubt it now. However, like you I have no problems about believing in a Creator. I have abandoned many of my previous beliefs to find something that appeals to my logic. I now think that God made the Big Bang (or all Big Bangs) happen by setting the initial conditions and setting all the possibilities for each person and then leaving it to happen.

Evolution is then a consequence of God's Laws. It may be chaotic sometimes but so what? We don't see the Big Plan, we just see small parts of it.

I now think that God only intervenes for prophets, because they are 'the chosen ones'. If this sounds like the Matrix, this is deliberate.

However, we must question and question until our understanding and reasoning are satisfied.

Originally posted by Heronumber0
This may be the clue that I was looking for. However, we are still talking about Natural Selection here. There would have to be a selective advantage at each step of a mutation - even in a controller/regulator gene otherwise the idea flops. If there is no selective advantage to a penis developing if the female reproductive organ is not fully developed then the feature will be selected out!

Originally posted by andy1033
Ask yourself how can the reproductive process be so perfect(i know there sometimes are things wrong), and how males and females came into being. I suppose its the chicken and the egg.

Interesting conversation to be sure. Allow me to interject again, by saying that there are species where only one gender possesses external reproductive organs, such as squid, and there are yet more species where the reproductive organs serve more than one purpose, such as certain types of spider.

Something else to think about.

Originally posted by Heronumber0
Firstly, how did the sperm evolve a protective mechanism (prostatic fluids etc..) against a place (the vagina) that it has never seen before- and develop an acrosome that helps to cut through the egg?

This seems easily understandable to me... before this evolution occurred, sperm had a much harder time making it to the inside of the egg, and therefore the conception/birth rate was much lower. Then somewhere along the line, certain mutations occurred by chance which gave at least one individual organism's sperm the necessary prostatic fluids or acrosomes to stand a much better chance of fertilizing the egg. Because this organism was able to pass on these mutations to its offspring, the fertilization rates of all its descendants shot through the roof and eventually the rest of the population without the mutation became a minority and died out. I don't know if you're willing to accept the existence of these chance mutations, but thats what the whole concept of evolution is based on.

Originally posted by Heronumber0
Secondly, how did the penis and vagina evolve after the requisite millions of years of evolution and selection? How did the organs develop a gradual mechanism that would give a quarter vagina a selective advantage?

For example why would a half penis be more selectively advantageous than a quarter penis?

I suppose I am looking for possible mechanisms because it is a complete puzzle to me.

Well, if the scenario that madnessinmysoul suggested with the penis fencing is true, then that would explain the evolution of the vagina, and therefore two separate sexes. Organisms with some kind of mutation for a "receptor organ" aka vagina would have had a huge advantage in reproduction.

By Thousand

Interesting conversation to be sure. Allow me to interject again, by saying that there are species where only one gender possesses external reproductive organs, such as squid, and there are yet more species where the reproductive organs serve more than one purpose, such as certain types of spider.

Something else to think about.

There is some interesting material on what you said. I suppose what we can deduce here is that reproduction has evolved independently in different ways for different species. However, I can reiterate that organiser genes and possibly novel structures for making proteins from DNA may be a possible route for wide-ranging organ changes. Mutations in these organisers can cause major faults in reproductive organ development.

Originally posted by TheCosmicSerpent

This seems easily understandable to me... before this evolution occurred, sperm had a much harder time making it to the inside of the egg, and therefore the conception/birth rate was much lower.

There would still have to be a resproductive success otherwise the species would be 'outrun' by rivals. Remember there was probably a food chain in progress.

Then somewhere along the line, certain mutations occurred by chance which gave at least one individual organism's sperm the necessary prostatic fluids or acrosomes to stand a much better chance of fertilizing the egg. Because this organism was able to pass on these mutations to its offspring, the fertilization rates of all its descendants shot through the roof and eventually the rest of the population without the mutation became a minority and died out. I don't know if you're willing to accept the existence of these chance mutations, but thats what the whole concept of evolution is based on.

I am willing to accept that hter must have been some mutations however TCS, did the male and female develop side by side as andy said? Otherwise this scenario is a nonsense even though it is logically attractive.

Well, if the scenario that madnessinmysoul suggested with the penis fencing is true, then that would explain the evolution of the vagina, and therefore two separate sexes. Organisms with some kind of mutation for a "receptor organ" aka vagina would have had a huge advantage in reproduction.

Don't think that it is that easy. There would have to be a vaginal pouch of some sort to receive and safely store sperm and then there would have to be an operating ovary/egg scenario in place already. In other words, each layer of complexity reveals another layer. This is why I vaccillate between Intelligent Design and Creationism. Only molecular biology can come up with relatively sensible propositions at cellular and tissue levels. Organ development and evolution is a field in itself...

All the questions you have in your initial post about how these traits evolved are quite simple, just that at some point a mammal had a mutation or gene shuffling created something a little different, and that new trait was able to reproduce more and have a better chance of living. Seeing as we use our brains now to survive, our sexual organs haven't exactly evolved for many millenia.

Originally posted by ingeniouslycorrupt
All the questions you have in your initial post about how these traits evolved are quite simple, just that at some point a mammal had a mutation or gene shuffling created something a little different, and that new trait was able to reproduce more and have a better chance of living. Seeing as we use our brains now to survive, our sexual organs haven't exactly evolved for many millenia.

I don't think they are simple to explain at all. The OP still has not been answered in detail. Please tell me how evolution can cause sperm cells to go to a location where they have NEVER been by gradual genetic change. No one has answered that point to my satisfaction ingeniouslycorrupt.