Why Sperm Cells Are More Valuable Than Egg Cells.

[MMX2010]

I've noticed that a couple of posters have concluded that "Egg cells are more valuable, because they're rare." 

 

I would challenge that conclusion based on the following facts:

 

In evolutionary history, asexual reproduction existed long before sexual reproduction.  Asexual reproduction is beneficial because it's fast, cheap, and highly accurate; but it's highly problematic because it produces 100%-accurate genetic copies of oneself. 

 

Every highly genetically-similar species is in danger of becoming extinct.  If just one parasite or environmental factor is highly dangerous to one member of the species, then it's highly dangerous to all members of that species.  Therefore, sexual reproduction arose to create genetic variability within the species to protect it from the threat of extinction. 

 

Since every sperm cell and every egg cell contributes equally to human genetic-variance, then sperm cells are responsible for 99.9999999% of human genetic-variance.  (The average man produces 525 billion sperm; the average woman produces 400 eggs.  Total male variance equal 525 billion divided by 525,000,000,400.) 

 

Do you agree or disagree with my analysis? 

[J. D. Stembal]

Asexual reproduction isn't 100% accurate unless you ignore genetic mutations.

 

The theory that sperm are less valuable than eggs, at least in homo sapiens (and their genetic cousin, the bonobo), comes from the concept of sperm competition. At the dawn of man, we had no concept of microscopes or genetics. We liked having sex a lot, so promiscuity was the norm. Sex reinforces the social connections among family and tribes, and is the way we traditionally formed friendly alliances with others, which eventually evolved into the marriage contract as a way of keeping the peace and brokering important business deals. Going back to the idea of sperm competition, multiple males will take turns having sexual intercourse when the female is close to ovulation and presenting signs of arousal. Then, at the microscopic level, our boys jockey for position and avoid obstacles left by other men to be the first to get to the egg in order to fertilize it. Humans and the bonobo have the largest specimens of penis in the Primate Family due to this system of sperm competition. Larger penises (and accompanying testes) can deposit more sperm closer to the egg and the shape of the glans of the penis is designed to scoop out previous sperm deposits made before the sexual encounter.

 

The bottom line? Size matters, at least in terms of sperm competition. The institutions of marriage and religion were designed to subvert our natural inclinations for promiscuous sexuality, and to control them.

 

I recommend two good books on human sexuality and evolutionary psychology.

 

Sex at Dawn by Christopher Ryan and Cacilda Jetha & The Chemistry Between Us by Larry Young and Brian Alexander

 

http://www.sexatdawn.com/

http://www.goodreads.com/book/show/13588415-the-chemistry-between-us

[Pepin]

This theory is not inline with the evolutionary theory. A great book to look at is The Selfish Gene by Richard Dawkins, as it contains an explanation of gender and sex cell in regards to evolution.

[Heam]

The sexual reproductive paradigm is the reason for sexual variation, not sperm cells. Almost all of those hundreds of billions of sperm cells end up never fertilizing an egg, so they have no impact on the variability of the species and hence are expendable, just as nature designed them to be. This is illustrated by the fact that increasing sperm cells in a person does not mean there is an increase in variability in a population pool. Let's use this (perhaps uncomfortably graphic) example of Jim, Bob, and Sally

 

Jim and Bob are both trying to fertilize Sally.

 

The genetic distance between Jim and Sally is 1

 

The genetic distance between Bob and Sally is 2.5

 

 Note, greater genetic distance means higher variability in the genetic code of offspring

 

If I (have one of my medical assistants) take a sperm sample from Jim and Bob and create a solution containing 1 billion of Jim's sperm cells and only 1 of Bob's cells, then mix it in a dish with one of Sally's eggs...

 

...could we say that Jim's sperm is contributing more potential variability to a fertilized zygote than Bob?

 

The answer is no. So I disagree with your assertion that sperm is more valuable than an egg. In fact, that one of Bob's cells is more valuable than a billion of Jim's if we consider variability as our priority demonstrates just how cheap sperm actually is.

[Frosty]

I've noticed that a couple of posters have concluded that "Egg cells are more valuable, because they're rare." 

 

I would challenge that conclusion based on the following facts:

 

In evolutionary history, asexual reproduction existed long before sexual reproduction.  Asexual reproduction is beneficial because it's fast, cheap, and highly accurate; but it's highly problematic because it produces 100%-accurate genetic copies of oneself. 

 

Every highly genetically-similar species is in danger of becoming extinct.  If just one parasite or environmental factor is highly dangerous to one member of the species, then it's highly dangerous to all members of that species.  Therefore, sexual reproduction arose to create genetic variability within the species to protect it from the threat of extinction. 

 

Since every sperm cell and every egg cell contributes equally to human genetic-variance, then sperm cells are responsible for 99.9999999% of human genetic-variance.  (The average man produces 525 billion sperm; the average woman produces 400 eggs.  Total male variance equal 525 billion divided by 525,000,000,400.) 

 

Do you agree or disagree with my analysis? 

 

Disagree.

 

It's correct to say that males create more genetic variance in their sperm, it's not correct to say that contributes to the overall gene pool. How much genetic variance is created is not the same as how much is effectively used to create new offspring. Only 1 sperm and 1 egg are used in typical conception, so the genetic variance is 50/50.

 

The argument about that eggs are more rare is that there's a much more limited number created and so there's less chances for conception, they're also kept artificially rarer by the host (the female) because it's in her best interest to limit availability in order to ensure the eggs are spent on the best partners to produce the best offspring. Another reason for females artificially making their eggs rarer is because it's a big risk having a child as the child requires a lot of resources from the mother and creates a large inconvenience.

 

Usually this argument is used to explain the asymmetry in sexual behaviour, men are more promiscuous given the chance, where as women are more careful and selective. This leads to asymmetry in social values and generally puts women in control of sexual partner selection.

 

*edit*

 

Oh I should add that theoretically the amount of genetic variance you can produce without mutation is 23 pairs of chromosomes with each having a potential chance to come from either your father or mother, so you have 2 arrangements of 23 pairs or 2^23 which is 8,388,608 possible genetic variance from the father or mother.

 

With an average number of sperm in a single ejaculation being 40m to 1.2Bn you can see that simple laws of average state that a huge number of these are redundant. But the process by which chromosomes make it into the egg or any one sperm to my knowledge is random, so when it comes to genetic variance the contribution is still 50/50.

 

Fun fact, when you combine 8,388,608 combinations from each parent you get a about 70 trillion unique offspring, so there's a 1 in 70 trillion chance that if you give birth a second time the 2nd child will be genetically identical to the first!

[Pepin]

To clarify, when you speak of variance, do you mean probability of mutations? As far as genetic shuffling goes, the amount of sperm or eggs produced does not matter. But in terms of mutation, it may be valid to say that sperm contribute more to mutation according to some studies. Provided this is true to some extent, it wouldn't imply that sperm are more valuable, as the mutation is likely to have no effect or a negative effect. Positive mutations do occur, but they would have to occur at a far higher rate in order to increase the value of sperm.

 

I suppose the argument could be made that the increase mutation rate in sperm could play a role in certain circumstances of species survival. If sperm mutation was dominate in an insect species and pesticide was being used on them, it would be more likely for the sperm to contribute to resistance to the pesticide as opposed to the egg. Again, this would not imply that sperm is more valuable, as value is a different concept the above posters explain.

[OzTrAlien]

Asexual reproduction isn't 100% accurate unless you ignore genetic mutations.

 

Mutations are ignored on the basis they are variations which are not naturally occurring, ie: blue eyes are a mutation, they are not a natural derivative of the genetic pattern but a mutation in the gene , as Stefan puts it, they are "tall asians" a variation not what is considered normal.  

 

Much like how all cheeters(the cats) are genetic duplications or replications, any organ or living tissue from one cheeter can be used or donored to another without any rejection from their body, they may have variations in their spots but it is much like how genetic twins have small variations these are not considered mutations, however even twins can suffer compatibility issues which cause rejection of body organs . 

 

 

 Then, at the microscopic level, our boys jockey for position and avoid obstacles left by other men to be the first to get to the egg in order to fertilize it. 

 

It is not the first sperm to reach the egg fertilizes it, many sperm reach the egg at approximately the same time, the whole surface of the egg will become covered in sperm, all the sperm begin to spin and rotate the egg in unison somewhat like a "mating dance" while in this process a single sperm is chosen and then allowed to enter the egg's outer wall, it is not yet understood as to how or why only this single sperm is chosen or why the opening is created by the egg to allow only this single sperm to enter the egg, but it is known the sperm can not force their way through the outer layer of the egg wall. 

 

There is no jockeying for position or obstacle created through insemination by others, for example, a female cat will have multiple male inseminations while on heat and while the ratio of each males sperm group which reach the eggs and on each egg may vary, the whole of the multiple male sperm mix take place in the "mating dance", hence all the sperm groups are involved and beneficial in the reproduction process, in essence it is helpful to all, much like how geese flying in formation is helpful to the whole group, the grouped sperm help to carry along the seminal fluid which is beneficial to survival of the sperm groups.

 

In the charge from bagdads, on route to the golden egg there is no  "system of sperm competition."

 

 

 Larger penises (and accompanying testes) can deposit more sperm closer to the egg and the shape of the glans of the penis is designed to scoop out previous sperm deposits made before the sexual encounter.

 

The "head" of the penis is designed to facilitate entry into the vagina, not to scoop out other sperm deposits, our reproductive organs are inherently still based on our quadapedial ancestry, where "doggy style"(descriptive term) intercourse for reproduction was the "natural by design" position, when in this position the erect penis slides up between the labia minora and the smaller less ramped part of the penis gland will lodge in the fold of skin on the vagina created where the labia majora and labia minora meet, it is held there directly at the opening of the vagina, the foreskin is to retain moisture in this area to facilitate entry, as entry takes place the foreskin will be pushed back over the gland and held back there by the corona to prevent it moving forward and interfering with the path of ejectulation, the gland or more so the corona is not a scoop to pull other semen out of the vagina, normal modus operandi of intercourse for reproduction is insert once till ejectulation then remove, not put in, pull out like scooping dirt out of a bucket. 

 

Due to the design of the vigina based on our quadapedial evolutionary path you will notice this places the cervix at the bottom of the viginal cavity when in a "doggy style" mating position as the woman lowers her front body position gravity will pull her internals forward this helps to open up the viginal area inside to allow the ejeculate to have a free path to the well created by the cervix to catch sperm and aid their journey into the uterus area to meet the egg, a larger penis is not going to enter the cervix to shorten the distance any sperm must take beyond the cervix to reach the egg, it will make the path of the ejeculate shorter but it wont make any path by the sperm shorter compared to any size penis ejeculating onto the cervix well.

 

There are animals in nature which use their penises to cause abortions of offspring from older alpha males, when they become the Alpha Male of the group, ie: like Zebras, but this is hardly what could be considered "for" or "aids" reproduction.

 

While i could add further information on matters like where you mention arousal or discuss the changes in the fluid excreations from the cervix during the normal cycles of reproductive organ maintenance and readiness i don't want what i have said to lead away from the OP's topic

 

It is also known that sperm from any male can be placed in any egg, once the nuclei of the egg has been removed and this will allow for reproduction of a different species within a host "mother", ie: from a male human, using either the female or male sperm, could then be placed into a pig or cow egg that has had its nucleus removed and once placed back into the host "mother" will allow for the gestation of the new human being, though artificial sperm can be created through the use of female or stem cells, this sperm must be used in a natural human egg containing the human nuclei and placed into the native female of the egg for it to produce a human being.

[MMX2010]

Thanks very much for your responses and book recommendations.