How did sexual reproduction come to be (from an evolutionary standpoint)?

The theory of evolution in itself, to a very large extent, rests on living beings ability to sexually reproduce. But not much is said of how this mechanism arose in the first place.

I've always wondered how evolution explains how sexual reproduction came to be. I'd like to know how exactly complimenting male and female cells developed and then went on to be able to produce offspring... after a gestation period.

So far, my internet searches have only yielded various speculations on this subject. As we all know we cannot take speculation of what went on millions of years ago, as confirmed fact.

reply to post by sk0rpi0n


Interesting thought. I've questioned this too... Especially since single-celled organisms are typically asexual, and just self-reproduce without fertilization or sexual division. If everything evolved from single-celled, asexual roots, what's the purpose of sexual division?

Sorry I don't have any answers for you, and I'm sure everything you'll find is speculation because all we have are best guess scenarios. Selective breeding is important to carry on "good" genes, but I'd say if something was asexual and able to survive and reproduce, isn't that good enough?

I'm sure you've already read this, but it seems like a good basic introduction to the topic for anyone else curious: Evolution of sexual reproduction

the sperm goes down the fallopium tube thing then when it reaches the egg it does mitosis or somethin then a baby is born

reply to post by sk0rpi0n

The majority of components that lead to life's diversity are auto-catalytic. There is rarely a cause and effect, but things are happening concomitantly, and the effect is merely a by-product.

Sex evolved as a response to pressure imposed by parasites (any entity that exists at the expense of the host). Some organisms can "choose" their sexual behavior based on parasite intensity. In an area devoid of parasites, they reproduce asexually, and sexual reproduction occurs where parasites are densely populated.

At any point when two primordial cells "fused" into a new cell with a split share of genetic information from each parent cell, it widened the genetic variation with which to resist parasites, thus being favored by natural selection. Subsequently meiosis even further strengthened the fight against parasites.

Originally posted by uva3021
reply to post by sk0rpi0n

 

The majority of components that lead to life's diversity are auto-catalytic. There is rarely a cause and effect, but things are happening concomitantly, and the effect is merely a by-product.

Sex evolved as a response to pressure imposed by parasites (any entity that exists at the expense of the host). Some organisms can "choose" their sexual behavior based on parasite intensity. In an area devoid of parasites, they reproduce asexually, and sexual reproduction occurs where parasites are densely populated.

At any point when two primordial cells "fused" into a new cell with a split share of genetic information from each parent cell, it widened the genetic variation with which to resist parasites, thus being favored by natural selection. Subsequently meiosis even further strengthened the fight against parasites.

"Sex evolved as a response to pressure imposed by parasites"

I see...and you conclude that basis what exactly? Agreed, it indeed makes for a rather colorful speculation given the complex nature of this subject, but would you take this as a 100% confirmed fact? Can you direct me towards a source documents that make this claim?What are the credibilities of the source?


"At any point when two primordial cells "fused" into a new cell with a split share of genetic information from each parent cell,,,,,"

And just how did this fusing occur? Am I to believe that the male and female cell developed to be compatible with each other simultaneously before the very first act of sexual reproduction occured? Or were there any errors along the way? Any thing I can google up? And what about gestation? Did nature get the very first instance of gestation right the first time??

It's so easy

I wanted to always know that too...

I think what you mean is how did cells go from replicating by "themselves" to manual reproduction...
Don't have a clue. lol.

The chances of their being two dogs, humans or whatever to evolve at the EXACT SAME TIME IN HISTORY and be complete gender opposite enough to reproduce doesn't seem logical.

Originally posted by CanadianDream420
I wanted to always know that too...

I think what you mean is how did cells go from replicating by "themselves" to manual reproduction...
Don't have a clue. lol.

The chances of their being two dogs, humans or whatever to evolve at the EXACT SAME TIME IN HISTORY and be complete gender opposite enough to reproduce doesn't seem logical.

Careful now, dont use the "L" word... I heard its (c) and (tm) of those who DON'T doubt that sexual reproduction evolved.

reply to post by CanadianDream420


There's several hypotheses. A likely one is that species developed male and female genital parts...and some species still show these traits. Slugs...mussels...

Originally posted by MrXYZ
reply to post by CanadianDream420

 

There's several hypotheses. A likely one is that species developed male and female genital parts...and some species still show these traits. Slugs...mussels...

Ok so, does that mean its been confirmed as to how how sexual reproduction evolved? Also, any info on as to why they started to develop male and female genital parts in the first place?

Even if slugs and mussels show these traits, how does it explain how and why they started to develop male and female genital parts?

reply to post by sk0rpi0n


This article does a pretty good job at explaining it...including mentioning how far science has come in figuring it out.

LINK

Originally posted by sk0rpi0n
those who DON'T doubt that sexual reproduction evolved.

It's pretty clear it did evolve, we have evidence of that...the "why" is another can of worms, if an answer to that question even exists.

Originally posted by MrXYZ

Originally posted by sk0rpi0n
those who DON'T doubt that sexual reproduction evolved.

It's pretty clear it did evolve, we have evidence of that...the "why" is another can of worms, if an answer to that question even exists.

1. If its "pretty clear that it evolved", then why did you provide me a link which starts off with "the evolution of sexual reproduction is currently described by several competing scientific hypotheses..."?
Also, what is the evidence that you speak of?

2. You also recently mentioned in another thread in the "origins" section that you "need facts and objective evidence to believe in stuff, otherwise they're nothing but fictional stories..."
www.abovetopsecret.com...

So, at what point should one start taking "competing hypotheses"(as mentioned in the link YOU provided) as "facts and objective evidence"?

reply to post by sk0rpi0n


Well, we know that sexual reproduction evolves because we can trace back species.

For example, we know that around 110mil years ago, placent mammals split from marsupial mammals. When that happened, sexual reproduction evolved too. Marsupial females have 2 vaginas for example. The ancestor of mammals and marsupials didn't have 2 vaginas...it's something that EVOLVED over time.

Of course sexual reproduction evolves, as species evolve too and new species constantly go extinct or come into existence.

Originally posted by MrXYZ
reply to post by sk0rpi0n

 

Well, we know that sexual reproduction evolves because we can trace back species.

For example, we know that around 110mil years ago, placent mammals split from marsupial mammals. When that happened, sexual reproduction evolved too. Marsupial females have 2 vaginas for example. The ancestor of mammals and marsupials didn't have 2 vaginas...it's something that EVOLVED over time.

Of course sexual reproduction evolves, as species evolve too and new species constantly go extinct or come into existence.

You've only said "sexual reproduction evolved" thrice in your post without even addressing the basic premise of my original post.

I'd like to know how exactly complimenting male and female cells developed and then went on to be able to produce offspring... after a gestation period...

Now try looking beyond 110 million years... how exactly did the whole mechanism involving male-female cells start to originate?

reply to post by sk0rpi0n


Again, there's several hypothesis you can read about in the Wiki article (1st result of my link). There's no definite answer, just like there's none to answer "how did life start in the first place?"

How did sexual reproduction come to be (from an evolutionary standpoint)?,

Well . . . it started with some idle chit chat at work during break and one night I asked if she'd come to dinner . . . . a few nights later, we stopped at a bar after work and had a couple-a-six or so beers and she jumped me in the taxi.

Blammo.

Hello parenthood.

Originally posted by sk0rpi0n

Ok so, does that mean its been confirmed as to how how sexual reproduction evolved? Also, any info on as to why they started to develop male and female genital parts in the first place?

Sexual reproduction happened before slugs, I believe, in the order of things, although I am not entirely au fait with the order of things. Plants reproduce sexually. As do alot of fungi. They also have the ability to self-replicate too, usually. Mammals are alone in solely requiring both the male and female for reproduction. Birds, reptiles, fish, etc, can all reproduce asexually given the correct stimulus even if they normally favour sexual reproduction.

Genitals are no different to the parts on flowers and serve the same purpose depending upon the sex of the plant.

Originally posted by KilgoreTrout

Originally posted by sk0rpi0n

Ok so, does that mean its been confirmed as to how how sexual reproduction evolved? Also, any info on as to why they started to develop male and female genital parts in the first place?

Sexual reproduction happened before slugs, I believe, in the order of things, although I am not entirely au fait with the order of things. Plants reproduce sexually. As do alot of fungi. They also have the ability to self-replicate too, usually. Mammals are alone in solely requiring both the male and female for reproduction. Birds, reptiles, fish, etc, can all reproduce asexually given the correct stimulus even if they normally favour sexual reproduction.

Genitals are no different to the parts on flowers and serve the same purpose depending upon the sex of the plant.

Thats fine ..but my main point in the OP was..

I'd like to know how exactly complimenting male and female cells developed and then went on to be able to produce offspring... after a gestation period.

Im talking about origins of the mechanism of sexual reproduction. Not about basic stuff about genitals being no different from flower parts.

Most of the stuff Ive found on google searches are speculation and guesses... with obviously no way to confirm it.

reply to post by sk0rpi0n
You tell us how are we to confirm something that happened 2+ billion years ago? Unless it is recreated in the lab then I'm sorry by your qualifications for being satisfied you will be forever underwhelmed. We can have a hypothesis and study how and why sex is sustainable in organisms that have contingent sexual/asexual behavior. The leading theory (yes its been upgraded to theory) is sex and parasites. The fusion of two sex cells is not a conscious activity that happened because some event occurred, it happened accidentally many different times, but there was a specific time where the intensity of parasites allowed the fusion to have selective advantages.

Mutation A spreadsbecause of event B, not Mutation A occurrs because of event B.

What is interesting, based on studies now leading to great assertions of proof regarding mammals on what happens in utero, the embryo is a parasite to the mother, and actually elicits an immune response. The father's sperm provides the placenta and without the father's genetic imprints (genes for essentially saying "baby, take more food from mother than what would otherwise occur") the baby will be malnourished and mentally retarded (The mother actually imprints genes with the instructions "don't let this baby have any food"). Various species of mice have been the unfortunate victims of such a study, with considerable results. And the evidence is strong to anticipate similar devices are in play for all other mammals, including humans, as well.

You have to remember females got along just fine for billions of years without the male, however, today it appears that, on average, genes do a lot better with the facilitation of multiple sexes as opposed to one.

There are thousands of studies, books, and papers, that have resolved most if not all of the variation in the maintenance of sexual reproduction as negotiating a response to parasitic pressure.

I would suggest reading "The Evolution of Sex" by Maynard-Smith, or "The Red Queen" by Matt Ridley