Meiosis to Mitosis - Evolution's unsolved riddle of the origins of sexual reproduction.

The one glaring gap in evolutionary theory that persists to baffle us is exactly how we went from asexual (meiosis) to sexual (mitosis) reproduction. There is many theories floating about in the scientific community but we have still not "nailed it down" definitively. I am studying evolution as a layman and I know the religious community loves to point out this "gap" in our current understanding. Of course a lack of understanding is not grounds to jump to conclusions in the form of automatically assigning supernatural causation- the God Did It complex. They have it so easy on the other side. If anyone else has delved into this subject I would be open to suggestions about various information sources to check out. I did find one location at a Xtian apologetics website where they discussed current secular theory on sexual reproductive origins. It was an interesting read because they stayed with the facts for the most part and left their own commentary to a minimum. It is astonishing that the individuals who contributed to the article have doctoral degrees but still cling to the "young earth creationist" theory. I verified this by emailing them as I was unsure at the time if they were really proponents of young earth theory. And I know it is irritating to even embellish notions of a young earth argument with the title of "theory."

https://www.apologeticspress.org/apcontent.aspx?category=9&arti...

Some of these sexual origin theories are no longer as popular as they once were. I believe the "red queen" theory is still looked at favorably. At any rate I find it all very engrossing and intriguing.

What will be the breakthrough that gives us the additional insight into just what happened a billion or so years ago that set the stage for sexual reproduction to gain a foothold and become the preferred way to ensure our DNA was being carried forward faithfully? Inquiring minds want to know.....

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I think of mitosis vs meiosis as body building vs seed generation. There's chicken and egg conundrum here that goes back millions of years (i.e. "which came first"). But ignoring that question for now, it's essential to understand:

1) The mitosis/body building functions in a single organism to grow from a seed, develop into an adult with dozens of different cell types and tissues, then die off from injuries and eventual old age. They're versatile but disposable in the long run.

2) The meiosis/seed generation functions across generations, in a way such that the DNA in each sex cell (e.g. male sperm and female ovum) is copied only in its pristine, virgin form, and not used in any way until it's time to make a seed for the next generation. E.g. in mammals (at least), every female ovum is already present in the girl baby as soon as she's born! These cells are not so disposable, but remain as perfect as possible from one generation to the next.

Hence organisms get diseases (like cancer), grow up and die off in long-lived lives, while sperm and ova remain faithful copies of what the organism was originally born with. That's the main advantage of having both meiosis and mitosis.

Most non-sexual life forms like bacteria have no mom and dad's variety of genes, but can share genes between other bacteria in the community before they reproduce by simple splitting in two. Their single strand of DNA (in the form of a ring, in fact) provides for faster gene mixing than meiosis, but leads to more disposable offspring.

The advantage of sexual reproduction is a question we're still working on, but perhaps it's because meiosis makes it possible for each organism to save stable genetic code from one generation to the next, in spite of long-lived (but eventually disposable), complex cellular development via mitosis in each single organism.

I'm not a biologist... corrections/amendments appreciated! Meanwhile, try explaining that to people dead set on just falling back onto their Godidit "explanation" of how the world must work, damn the science.

Forgot to add... to understand when and how sex first took off, if I remember my college Bio correctly, I think it was back when simple green algae evolved from ocean to land conditions and needed to rely on air to carry male sperm (and/or spores) by the wind. If that's not totally correct, it's still important to understand when and how sex first evolved, and the complexities of what came later is a different topic.

I just heard a podcast last night of some YEC guy mocking evolution by conflating all kinds of unknown "evolutionary" processes from the big bang to human genetics. "Seven different kinds of evolution", he said, breaking it down in a way to point out at least seven ways Genisys can defeat popular "scientific evolutionary theory".

My explanation may be overly technical for lay persons. But here goes.

Them so hawny.

Long time. 

I mostly agree with y'all, but sex probably became the next big thing way back over a billion years ago, evolving even before multicellular organisms evolved. See here. It probably started merely as a more efficient way to exchange genes or other materials, where each single cell of the pair evolved to give it rather than receive it, and vise-versa. That's when male "competition" may have started, but (as in flowering plants) there was no social stuff going on other than pheromones and other accidental bumping into each other.

I imagine I'm putting most readers to sleep?

I don't know anything on the subject, but I'm wondering if possibly it was an adaptation for social reasons. You know? It has been proven that having fathers involved in their kids lives makes them healthier. We "need" each other and are social beings, so maybe reproduction is just part of that too. We had to evolve as social in order to survive?

My pet theory is that it's all about COMPETITION.  Competition increases fitness.  The fittest survive.  Evo-fucking-lution.  If you think about it, why do males fight, much of the time?  Bingo.  Why are females bitchy to each other?  Voilà.  What about all those preposterous antlers, rutting fights, enormous peacock tails, status and dominance?  All to see who wins the girl. 

I read something interesting recently: something like "females control the pace of the mating process".  This is of course simplistic, yet there is a lot of truth in it.  It kind of implies that females' job is to look pretty, while the males fight over them, and she chooses the one she likes best.  This explains a whole lot about humans. 

I got this idea of sexual competition from the British phenomenon (Mrs Thatcher) of "competitive tendering".  Basically, you always know when you're dealing with a public department that has gone through competitive tendering (competition to see which organisation can do the job the best) - it's efficient and thorough.  The ones that don't tend to be wasteful, inefficient, overstaffed, underworked and ineffective. 

However much you like or don't like Mrs Thatcher, this process has revolutionised the quality of public services in the UK.  Of course, there are problems when the organisation that wins the contract can't really do the job, because they're novices trying to do it on the cheap.  It works best when the original department keeps the job but has to sharpen up its ideas in order to do so. 

Simon, just to clarify, "survival of the fittest" does not refer to the most athletic, it refers to fitness as suitability, not as health. Survival of the most suitable for current habitats, would probably be more accurate.

Strega, 

I'm re-reading "On The Origin of Species" and that is a central point in Darwin's hypothesis. Suitability to current/changing conditions is key.

I agree, that's what fitness means.  But in this situation, it also means "what the ladies like", no matter how wacky that ends up. 

In his book, Why males exist, Fred Hapgood attempts to answer this question of the evolution of sex.

"sex" is present in plants before animals, etc.  

The easiest way to think about 'survival of the fittest" is to NOT think about it as survival of the fittest critter, but of the INVOLVED GENES.

IE: As long as the GENES get passed on, whatever they code for, or used to, or one day might...is also passed on.

Why ARE there still possums when there are critters that do what possums do, better than possums do it?

Because they do it well ENOUGH to simply keep passing on the genes that make these possumy thingies.

If they don't get wiped out, they keep getting passed on.

(GENES)

So, we can see the progression of the GENES' progress through history...BECAUSE there are still some ancient wee beasties that are STILL plugging away with "Life 1.0" programming...they worked well ENOUGH, to keep passing those genes on.

Bacteria, etc, like roaches, etc, have SO many "bad copies" that most of them are rubbish...but so many are made at a time that it tends to overcome the waste rate.

People, elephants, etc, make very very few copies...but almost 100% are good copies.

If the environment changes, say, via vulcanistic or asteroidal catastrophe, climate change, tectonic relocations/mountains instead of oceans, etc...the good copies are good for ONE basic set of criteria, but may be unsuited for the new conditions, and get wiped out.

If you are running a crappy copy machine that cranks out zillions of copies, only half of which are good, for the old set of conditions, there's a much better chance that the messed up copies might have something better suited for the new conditions.

The "modern" peacock and sexual display type issues came WAAAY later, after dimorphism.

Again, don't give gender that much weight, evolutionarily, its a recent development.  MANY species can change gender as needed, etc, even in modern species.

It IS simply more along the lines of the way you might see taller/shorter/fatter/thinner versions of a critter.  Asian elephants are smaller than the African elephants, island versions of normally large critters, tend to become smaller, etc.

The more food/the larger the predatory threats, the bigger the critters tend to be...and if it stays wet and there's fewer aquatic predators and more food, a critter might shift its development to stay in an aquatic larval form (Late bloomer rewards, etc).

Dimorphism was just a form of the critter that did better in lean or waxing times...so, larger with defensive head protrusions, or smaller, etc...and, if the growth/protrusion aspects were mediated on a set of genes, then, gender is born.

That's WHY temperature DOES change the gender of hatching gators and turtles.  The temperature is a clue as to the environment they are being born INTO.

Its WHY some species have larger males, and some, larger females...the "gender" is really an arbitrary way of separating features, which, as humans, we tend to over weigh in importance.

:D

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