Can someone explain the evolution of sexual reproduction?

Question

First of all, I just want to say that I am not religious or "spiritual" in any way. I'm not trying to pick a fight with anyone. I legitimately want to understand this. Additionally, if you respond to this question by saying that evolution isn't true, I will completely disregard your response. My question is based on the premise that evolution is a reliable theory. If you wanna argue about the validity of evolutionary theory, please either do it somewhere else or email me and we'll have a private discussion on the topic. I apologize for beginning my question with this little rant, but I'd really just like to hear some well-informed responses from knowledgeable people. So here's my question:

How exactly did life make the jump to sexual reproduction from methods other than sexual reproduction? I can't imagine a way in which it makes sense for there to have been a "1st female" and/or "1st male." What am I missing? 

Okay, rant #2:
I really don't want the pet theories of people with no real understanding of biology. I just want the current theories, whatever they may be, that are the scientific community's generally accepted explanations of the origin of sexual reproduction. 

Thanks in advance to anyone who can help me out here. I will certainly appreciate it. And again, I'm sorry for being gruff, but every time I ask a serious question, I get bombarded by people who have no understanding of the topic I asked about. Peace.

secretsauce · Accepted Answer

>"I can't imagine a way in which it makes sense for there to have been a "1st female" and/or "1st male." What am I missing? "

First, the fact that sexual reproduction does not require males and females.  (To pick an obvious example, most flowering plants reproduce sexually, but do not have separate males and females.)

Second, that 'males' and 'females' gametes can emerge slowly from undifferentiated gametes ... one type of gamete getting smaller and smaller, which is better for mass production, while the other type of gamete is getting larger and larger for purposes of replication following fertilization.

Third, that a species where each individual has both types of sex organs, can slowly specialize until each individual has only one kind of sex organ.

So for these three reasons, there never has to be a "1st female" and a "1st male."   What we call 'male' and 'female' seems like a clear dividing line only when we look at species like ourselves.  Once you take into account all the many types of living organisms in the world, and the MANY different systems they use for reproduction ... the words 'male' and 'female' do not represent a huge chasm, but two specializations that can emerge *slowly* over time from species with no specialization.

As follows:

>"How exactly did life make the jump to sexual reproduction from methods other than sexual reproduction?"

No "jump."

1. Asexual reproduction, to a combination of asexual reproduction with occasional exchange of genetic material (as we still see in bacteria).

2. Then species that can alternate between asexual and sexual reproduction (as we still see in such organisms as the slime mold amoeba, or various fungal spores, or even some insect species like aphids).

3. Then a slow transition to where sexual reproduction is predominant, and the organism alternates between diploid and haploid states.

4. Then a slow specialization of some smaller gametes better for mass production (sperm or pollen) while others get larger and better for replication following fertilization (egg cells or ova).

5. Then a slow specialization of organs for producing one type of gamete or the other (where all individuals have both types of sex organ, as we see in plants, many mollusks, some fish species, etc.).

6. Then a slow specialization of individuals that produce one type of sex organ vs. the other (males and females).

7. Then slow differentiation of secondary sexual characteristics between the males and females.

The fact that we find examples of all of these systems in use in species *today*, is an indication that this is never a need to postulate a "jump" at any stage.

No "jump".

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P.S.  I would love to know WHY some people give this a thumbs down ... as not one of these people had the courage to post a counter-argument.

KTDykes · Answer

"How exactly did life make the jump to sexual reproduction from methods other than sexual reproduction?"

Bacterial reproduction includes a form of behaviour known as bacterial conjugation, which is sometimes somewhat misleadingly termed 'bacterial sex'.  It isn't sex, but it does result in genetic exchange between two (or sometimes more) organisms, and leads to some genetic material from a second party getting into descendants of the first organism.  Sexual reproduction is a refinement of bacterial conjugation.

(You'll doubtlessly appreciate why I didn't read all the extraneous comments this question came wrapped with.)

Bob D1 · Answer

KTDykes is correct.

Here's something else: Secrets of sexuality unlocked
Saturday, 02 April 2011
http://www.thecitizen.co.tz/business/14-international-business/9568-secrets-of-sexuality-unlocked.html

-----------------
While not exactly the answer to your question, the above article contains relevant subject matter.

See: Planarians
http://planaria.neuro.utah.edu/publications/Current%20BIology.pdf

See also: The Origin of Sexual Reproduction
http://www.youtube.com/watch?v=1w0FiwfyUMM
----------------
Best regards

calzrhe · Answer

I found like a good link dude.  I know I'm not answering your question because I don't know how to answer it but I found a good link that might answer it and I'm learning too at the same time.

? · Answer

That's a complex topic. 
Maybe you will find some answers there: http://www.youtube.com/watch?v=eGRmm3KQg18&t=2m26s

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Can someone explain the evolution of sexual reproduction?

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