Male and Female Evolution ???

[juantonwan]

For a project, my teacher assigned a writing assignment where we are supposed to explain how Males and Females came to exist separately, but mess perfect with one another.

 

I think my teacher may be a pro religion, but I don't know for sure. But I am having a hard time finding answers to the questions that we are supposed to use in our paper.

 

Did males come from females? Did males and females sprout up at exactly the same time? Males and females are so different so how did they evolve to match perfectly? If there wasn't both male and female at exactly the same time, to evolve at the same time, then the whole process dies in one generation? etc. etc.

 

I was reading something about how hermaphrodites prove Darwinian Evolution, but I don't really get this and don't know if I should use this in my paper.

 

Can someone help me on this? I am not necessarily trying to prove my teacher wrong, but I want to have some solid facts and science. I don't want a bad grade just for having different beliefs. But if I don't make a strong argument that might happen, I don't know.

 

Any input, articles, links etc. would be helpful. Thanks

[Mokele]

Some good terms to try in google are "isogamy" (having same-sized gametes) and "anisogamy" (different sized gametes). Both are sexual reproduction methods, but only in the case of the latter can there be said to be males and females.

 

Using those terms, you should be able to turn up quite a few pages about the evolution of sex and the sexes. Feel free to ask questions about what you find.

[juantonwan]

So are their maps of how male and female humans came about?

 

Example:

 

Hermaphroditic organisms

Hermaphroditic organisms mutate

One organism mutates with more male traits, one mutates with more female traits

Base on environment, organisms mutate into vertebrates

Male and female vertebrates - great apes

Great apes evolve into humans

 

 

Please forgive my vagueness and/or ignorance. But could someone help me break down a more in depth map on how male and female humans came to be? Thanks very much.

[iNow]

First, remember that the differentiation between males and females happened WELL before humans ever came on to the scene. So, if you're looking for the first split between males and females, regardless of species, please clarify.

 

However, if instead you are referring only to humans, then your question seems more related to issues of embryogenesis.

 

 

Here's a few simple articles on sexual differentiation which clarify that process pretty well:

http://en.wikipedia.org/wiki/Sex_determination_and_differentiation_%28human%29

 

http://en.wikipedia.org/wiki/Sexual_differentiation

http://en.wikipedia.org/wiki/Embryogenesis

[CharonY]

And if your question is how sex evolved, well it is pretty complicated (with hardly any simple answers). One interesting bit is the possible involvement of mobile genetic elements.

For example transposons:

http://content.karger.com/produktedb/produkte.asp?typ=fulltext&file=CGR20051101_4372

 

http://www.nature.com/nrg/journal/v2/n8/full/nrg0801_597a.html

[juantonwan]

So basically single celled organisms mutated and evolved, eventually creating males and females. More genders could have been created, but since more that two would be problematic, male and female became dominant. Then over time those male and female organisms became more complex and evolved and mutated into various plants, mammals and reptiles?

 

So as a map, you could do something like this below?

 

Single celled asexual organisms

Mutated and evolved single celled organisms to multi-celled, multi-gendered

Male, female and hermaphroditic multi-celled organisms

Evolution of plants, reptiles and mammals with two genders

[juantonwan]

From:

http://www.space.com/scienceastronomy/solarsystem/origin_sex_010710.html

 

"Roughly 1 billion years after the first organisms romped in the hay, the

origin of sex remains one of biology's greatest mysteries. Scientists can't

say exactly why we do it, or what triggered those initial terrestrial

flirtations. Before sex, life seemed to manage fine by employing asexual

reproduction -- the cloning of offspring without the help of a partner.

 

Now a new study out of Caltech and NASA's Jet Propulsion Laboratory has used

digital organisms to simulate life before sex and yielded a possible

mechanism for instigating Earth's first courtship.

 

Intimacy never sounded so stressful.

 

Comet or asteroid impacts could have stressed asexual organisms enough to

send them down the path of sexual reproduction after forcing a flurry of

genetic mutations, the study shows. Heavy doses of radiation might also have

done the trick."

[juantonwan]

How important is the origin of sex, to evolution theory?? I would think it is pretty important, but I keep getting different answers and hearing different theories? Are there any hard facts I can use, or do I just have to pick the best hypothesis?

 

Why did the earliest asexual organisms feel the need to bump into each other (exchange information)? Why can't asexual, either multi or single celled, organisms mutate and evolve just as sexual, multi-gender organisms supposedly did? In fact, wouldn't asexual organisms reproduce faster, allowing them to evolve and mutate if they were in a harsh or changing environment?

[Mr Skeptic]

For a project, my teacher assigned a writing assignment where we are supposed to explain how Males and Females came to exist separately, but mess perfect with one another.

 

Tell that to a couple that has been married for a while...

 

I think my teacher may be a pro religion, but I don't know for sure. But I am having a hard time finding answers to the questions that we are supposed to use in our paper.

 

There really isn't much to say from a religion standpoint. Um, Eve was made from Adam's rib, and the rest of the paper is blank?

 

Did males come from females? Did males and females sprout up at exactly the same time?

 

Females are more vital because they are specialized for making babies. For the first bit of development, a male will completely follow the female body plan, until eventually the Y chromosome becomes active. In a species of lizard, there are no males. But before male/female come hermaphrodites.

 

Males and females are so different so how did they evolve to match perfectly? If there wasn't both male and female at exactly the same time, to evolve at the same time, then the whole process dies in one generation? etc. etc.

 

Co-evolution, my guess is that a hermaphrodite species slowly changed to emphasize one sex over the other.

[juantonwan]

So the theory is that the Earth was very hostile, unpredictable and dangerous early on, and it was too much for asexual organisms to survive? So instead of continuing to reproduce asexually, they started exchanging DNA to reproduce organisms that had mixed genes to better adapt and evolve? But if the asexual organisms couldn't evolve and survive the harsh environment, why would exchanging DNA with similar asexual organisms that can't evolve or survive the harsh environment, make a difference and/or allow them to change and evolve?

 

So now do we have to look at the origin of multicellular organisms? It seems that single celled organism would have had to evolve into multicellular organisms, prior to the evolution of sex.

[iNow]

So the theory is that the Earth was very hostile, unpredictable and dangerous early on, and it was too much for asexual organisms to survive?

Almost. You're very close. The hostility of the environment did impact future generations. Asexual organisms survived, but they did not do as well as sexual organisms did. The reason for this is because all asexual organisms were the same, and a bug or disease which killed one could kill them all. However, with sex, you have variation introduced by the mixing of DNA, and some of those variations can help to successfully fight off the same illness which killed the asexual organisms.

 

It's sort of like growing a garden. If you plant all one type of plant, and something happens like a bug attacks it or the heat is too much for it, then they all die and you don't have anything to eat. However, if you plant many different plants, some might survive the bugs and some might do better in the heat, so by introducing variance (different plants) you have a better chance at having food later because some will survive even if others are killed.

 

It's sort of the same with DNA. By mixing it up, you maximize your chances at being successful, whereas if you asexually reproduce your DNA stays the same and may not be enough to win the battles of evolution.

 

Just be careful not to ascribe purpose or intention to this. Organisms don't "choose" to adapt, it's more that those who were lucky enough to have the right set of genes and behaviors out reproduced those which did not, and the winning strategy becomes more common over time.

[Mr Skeptic]

So the theory is that the Earth was very hostile, unpredictable and dangerous early on, and it was too much for asexual organisms to survive?

 

That is not necessary for sexual reproduction. However, the major strong point of sexual reproduction is the formation of a gene pool, and the mixing of the genes, gives sexually reproducing creatures a huge boost in adaptability and evolution. This because there is more diversity, and also because the species as a whole can adapt rapidly by changing the ratio of genes in the gene pool (via a large portion of the genes which at the time are inconvenient being eliminated).

 

The boost to evolution rate is because each gene is separated from the whole genome. Thus various different beneficial mutations can be passed on separate from the rest of the genome which may be mediocre or even have bad mutations. Also less loss of genes, since with changing conditions sexually reproducing organisms can change gene combinations rather than entire genomes.

 

So now do we have to look at the origin of multicellular organisms? It seems that single celled organism would have had to evolve into multicellular organisms, prior to the evolution of sex.

 

Not really.

[CharonY]

To be fair, evolution of sex is a very complicated topic. Much too advanced for something like a highschool assignment. What iNow implies is that recombination via sexual reproduction may increase variance and hence increase fitness. The problem however is that sexual reproduction is associated with a two-fold cost compared to asexual reproduction. Moreover, even asexually reproducing organisms have means to increase variance by horizontal gene transfer, and finally as far as I am informed there is precious little data that supports the notion that sexual recombination actually does increase fitness. Some studies suggest that sex may have originated from genomic parasitism. See for instance:

Hickey DA, Rose MR: The role of gene transfer in the evolution of eukaryotic sex. In The Evolution of Sex. Edited by: Michod RE, Levin BR. Sunderland, Mass.: Sinauer Associates; 1988:161-175

[dr.syntax]

reproduction is that in so many instances it ensures that only the most fit males are allowed to enter the gene pool for one things All the many ways the males of so many different species have to fight it out with each other for the opportunity to mate : wallrusses,deer,wolves,bison,rams,lions,apes,chimps,elephants,hippos,horses and on and on. People also in thier own ways. At times they fight to the death in these struggles for the right to mate. The evolutionary benefit is that the genes of the most fit for survival are passed on most of the time. On the other side of it, those males want to mate with the attractive fit young females. And on and on it goes,that`s the way life is. Unkind,only concerned with survival and improvement of any species. I am getting old, no longer a desired mate. Am I wrong about any of this ? ..ds

[iNow]

Dr.Syntax - You seem to have missed the point of the thread a bit. The question is about how male/female splits came about as opposed to asexual reproductive approaches.

[dr.syntax]

means of change. Most mutations are not benificial. The advantages of sexual reproduction are obvious. ...ds

[Mokele]

Thank you for that useless and totally off-topic insight.

 

Read the other posts before replying, and make your reply on topic, or I'm going to start deleting your replies.

[jdcanfield]

Thank you for that useless and totally off-topic insight.  

 

Read the other posts before replying, and make your reply on topic, or I'm going to start deleting your replies.

 

And thus, an excellent example of the jump from physically dominant suitors to intellectually fit suitors was born. The game has changed my friend, adapt or you will be deleted.

 

This exchange says a lot about our modern gene pool without saying much at all.

 

Don't delete me; I will bring intelligence and flowers... later! 

[Chad]

For a project, my teacher assigned a writing assignment where we are supposed to explain how Males and Females came to exist separately, but mess perfect with one another.

 

I think my teacher may be a pro religion, but I don't know for sure. But I am having a hard time finding answers to the questions that we are supposed to use in our paper.

 

Did males come from females? Did males and females sprout up at exactly the same time? Males and females are so different so how did they evolve to match perfectly? If there wasn't both male and female at exactly the same time, to evolve at the same time, then the whole process dies in one generation? etc. etc.

 

I was reading something about how hermaphrodites prove Darwinian Evolution, but I don't really get this and don't know if I should use this in my paper.

 

Can someone help me on this? I am not necessarily trying to prove my teacher wrong, but I want to have some solid facts and science. I don't want a bad grade just for having different beliefs. But if I don't make a strong argument that might happen, I don't know.

 

Any input, articles, links etc. would be helpful. Thanks

 

 

 

 

Female homo sapiens (humans) came into existence, around 200,000 years ago.

 

And we are all related to a single human female. Science calls her mitochondrial eve.

 

 

Male Homo sapiens came into existence maybe 142,000 years ago.

 

The first male homo sapiens is called Y-chromosomal Adam.

 

 

Female Homo sapiens have been around at least 50,000+ years longer than the males.

Edited June 29, 2012 by Chad

[granpa]

some single celled organism ingested another of its kind (perhaps a spore)

and instead of being digested it it got released into the interior of the first cell

and the resulting diploid cell had some advantage that allowed it to survive and outcompete others

[Delta1212]

Female homo sapiens (humans) came into existence, around 200,000 years ago.

 

And we are all related to a single human female. Science calls her mitochondrial eve.

 

 

Male Homo sapiens came into existence maybe 142,000 years ago.

 

The first male homo sapiens is called Y-chromosomal Adam.

 

 

Female Homo sapiens have been around at least 50,000+ years longer than the males.

That is not how that works. The inclusion of the names Adam and Eve in those terms have become vastly misleading for some people. They were not the first anything.

 

Mitochondrial DNA is passed down through the remain line, and the Y-chromosome is passed down through the male line. Every male got his Y-chromosome from his father, who got it from his father and so on. Every person got their mitochondrial DNA from their mother, who got it from her mother and so on.

 

Mitochondrial Eve is the woman from whose mitochondrial DNA everyone alive today's mitochondrial DNA is most recently descended. That DNA can also be traced back to her mother, her grandmother and so on. Who mitochondrial Eve is changes over time as genetic branches die out. There were lots of other women (and an entirely different mitochondrial Eve that existed far back in their past) at the time of the current mitochondrial Eve. All of the descendants of these women, however, eventually died out or ended in a male who ceased to pass on her mitochondrial DNA.

 

By way of illustration, let's say there are two women: Eve and Lilith. Eve has a daughter and Lilith has a son. Theses two get married. Eve will be mitochondrial Eve for all of their descendants through her daughter, but that does not mean that Lilith didn't exist. Her mitochondrial DNA simply didn't get passed along because she had a son.

 

The same can be said of Y-chromosomal Adam. Y-chromosomes are passed down only through males. So if Adam has a son and Steve has a daughter, and the two get married, all of their male descendants will have Adam's Y-chromosome.

 

 

To illustrate how the specific Eve and Adam can change over time, let's say that Adam has two sons: Cain and Abel.

 

Both boys have Adam's Y-chromosome, so he is Y-chromosomal Adam.

 

Now let's say that Cain has two sons: Matthew and Mark.

 

Cain, Matthew, Mark and Abel all have Adam's Y-chromosome. He is still Y-chromosomal Adam.

 

Now Abel dies (of unspecified causes) without having any sons. Matthew and Mark are the only living male descendants and both have Cain's Y-chromosome. Cain is now Y-chromosomal Adam. This scenario also applies to mitochondrial Eve.

 

 

Humans existed long before either mitochondrial Eve or Y-chromosomal Adam existed, and neither was the first or only member of their sex which existed at the time, they are merely the individuals that, if you traced your lineage from your father to his father to his father etc, and your mother to her mother to her mother etc, you would intersect with every other person on those two individuals.

 

Everyone is still descended from other people who lived at those times, just not through a single unbroken line of one sex.

[Jaden]

Chad, I can see a major problem with your statement...

 

Female Homo sapiens have been around at least 50,000+ years longer than the males.

Humans cannot reproduce asexually. So how then do you propose that we survived for over 50,000 years without the ability to reproduce?

Do you think that women, for over 50,000 years, reproduced asexually to produce other women? And then one of them somehow spawned man?

This would be completely illogical, even impossible.

Edited July 4, 2012 by Jaden

[Ghost9]

I do not understand. If female is far more complicated then wouldn't male which is the simpler form evolve first.

 

 

 

Female homo sapiens (humans) came into existence, around 200,000 years ago.

 

And we are all related to a single human female. Science calls her mitochondrial eve.

 

 

Male Homo sapiens came into existence maybe 142,000 years ago.

 

The first male homo sapiens is called Y-chromosomal Adam.

 

 

Female Homo sapiens have been around at least 50,000+ years longer than the males.