What are the REAL differences between X sperm and Y sperm??
Updated 1-3-17
Conventional wisdom claims that X sperm and Y sperm are very different critters. Sure, they split from the same cells and matured in the exact same environment for 90 days prior to ejaculation, but somehow according to some of these theories, the second they leave a man's body, they begin to behave in dramatically different ways. Let's take these one at a time and see what the science has to say.
1) X and Y sperm are different sizes and shapes.
MOSTLY FALSE - It is true that X sperm are ever-so slightly bigger than Y sperm, because they carry 2.8% more genetic material (that tiny little arm of the X chromosome that is not present on the Y) and as a result their heads may be as much as 1% wider across or no different at all depending on the individual sperm. (sperm come in a variety of sizes). To put in perspective of how very small a difference that is, each sperm has 22 full sized chromosomes and then the 23rd which is either an X or a Y - the size difference is just that one tiny arm of the X. Everything else is the same between the X and Y sperm. (there's a good picture here Karyotype - Wikipedia - half of those chromosomes pictured are in X sperm along with the slightly bigger X chromosome, and the other half are present in Y sperm along with the slightly smaller Y chromosome). Not much of a difference.
Researchers have investigated this idea extensively in a series of studies and most have found no difference between the size and shape of X and Y sperm - not head length, not width, not area, tail length, or in any size or shape. And they checked this in both men with normal sperm and unhealthy sperm and found the exact same thing - NO discernible difference in size or shape (aside from the very small 2.8% difference in genetic material, of course)
Dimensional assessment of X-bearing and Y-bearing haploid and disomic human sperm with the use of fluorescence in situ hybridization and objective ... - PubMed - NCBI
Wiley Online Library: Not Found
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Quantification and classification of human sperm morphology by computer-assisted image analysis. - PubMed - NCBI
Here is one study that did seem to prove there were some subtle differences and that X sperm do seem to have a 1% larger head radius than Y do, but on balance, most researchers have not been able to find major differences between X and Y sperm.
http://molehr.oxfordjournals.org/con.../1/61.full.pdf
UPDATE!! A new study using highly advanced technology was able to differentiate between X and Y sperm using several variables having to do with size and shape. But please understand that these differences are SO microscopic that it still debunks the idea that X are big and slow, Y are small and fast. The researchers could not tell X and Y apart using size, shape, etc - it was only by combining ALL those things together and using the most cutting edge technology, that they were able to differentiate between X and Y. What this study is really saying is that X and Y are so similar in every regard that they are virtually indistinguishable and I believe this puts the "X big, Y small" to bed for once and for all. http://www.plosone.org/article/info%...l.pone.0059387
Where did this idea come from? Our old friend Dr. Landrum Shettles, who over 40 years ago looked at sperm through a microscope and noticed that there were some with fat heads and some with pointy heads and after trying to count chromosomes in them and giving up, jumped to a rather large, if understandable conclusion, that the fat heads were X and the pointy heads Y. More about Dr. Shettles' Big Mistake here: http://genderdreaming.com/forum/gend...le-timing.html
However, a good deal of much more advanced technology has been invented since then and researchers have since found that what Shettles believed were X and Y sperm, were in fact uncapacitated and capacitated sperm - sperm have to lose their round ends in order to fertilize an egg and undergo a process called "capacitation" after ejaculation.
http://humrep.oxfordjournals.org/con...4/880.full.pdf
There is NO way that anyone can look through a microscope and tell which sperm are X and which are Y. In fact, research on sperm is made very complicated by the fact that in order to observe sperm by basis of genetics, you have to alter them by using fluorescent dyes that may alter their actual characteristics. Keep that in the back of your mind whenever you read anything about sperm and how they behave, because a lot of researchers have been studying sperm that wasn't counted in advance of studying them (so who even knows what the percentages of X and Y sperm were there to begin with), weren't counted accurately after experimenting on them, and/or may have been altered in some way by the process of observing them.
2)X and Y sperm swim at different speeds
FALSE. Once Shettles decided that big and round = X and small and pointy = Y, he was off to the races. He decided that ~if~ X and Y were drastically different in size, that meant that X sperm were slow and Y sperm were fast and that is why he came up with his timing method. That's right, the ONLY reason anyone ever thought that timing intercourse mattered in gender ratio at all was because of one man's mistake. http://genderdreaming.com/forum/gend...le-timing.html
Now let's say for the sake of argument that Shettles could be ever so slightly right, Y are just a wee bit smaller. But as anyone who has ever watched the Olympics knows, athletes come in many sizes and shapes and just because an athlete is 1% larger than another athlete, does not mean that he/she will be 1% slower. Size can bring with it advantages as well as disadvantages.
Also, research indicates that while sperm do swim, the cervical mucus has currents in it that actually help move the sperm around to where it needs to go and that these currents may actually do more to bring the sperm to the egg than the motion of the sperm itself rendering any theoretical difference in speed largely meaningless anyway. In fact, some of the fastest-swimming sperm are dead on arrival (their purpose is not known, but it's probably not to fertilize eggs) and incapable of fertilizing an egg!! Given that 140-160 males are conceived for every 100 females, if Y sperm really were significantly faster than X, this is not what you would expect to see if Y sperm were really superfast and superfast sperm are incapable of fertilizing an egg.
3) X sperm are strong and live a long time and Y sperm are weak and susceptible to damage
FALSE. Again, Shettles, believing that the uncapacitated sperm were X sperm, assumed that since these "X" sperm were bigger, they were also stronger and hardier than Y sperm. Since this was all based on his misinterpretation of what he viewed, this idea is also completely false. Both timing and pH theory rely heavily on this completely disproven idea. http://genderdreaming.com/forum/gend...ph-pickle.html
In fact, research suggests that Y sperm may actually survive longer than X sperm in vitro. http://onlinelibrary.wiley.com/doi/1...1.00427.x/full
That having been said, X and Y sperm ~may~ capacitate at different rates and theoretically this could have something to do with gender ratio. It doesn't seem beyond the realm of possibility that timing intercourse or pH could play some part in this process. http://www.medical-hypotheses.com/ar...251-9/abstract http://journals.cambridge.org/action...ine&aid=183247
4) X and Y sperm swim differently
TRUE, kinda. When observed in vitro, X and Y sperm do seem to swim differently, even though they swim at the same speed. (IN COWS.) But it is not known how that translates to in vivo (in your body) conditions. Also, the numbers of sperm onhand seemed to affect how the sperm swam.
pH is often suggested as having something to do with this process but in the study below, pH is not mentioned and has NEVER been proven one iota to alter the way sperm swim, to "freeze their tails" or any such thing. http://genderdreaming.com/forum/gend...ph-pickle.html and http://genderdreaming.com/forum/gend...-insanity.html
http://onlinelibrary.wiley.com/doi/1...O;2-L/abstract
MOST of the action that moves sperm to the egg has nothing to do with the sperm itself. Muscle contractions, cilia lining your Fallopian tubes, and the movement of cervical mucus throughout your reproductive tract are all much more efficient ways of moving sperm than how the sperm swim anyway.
(Continued below - there is a whole very important second part to this essay that is down a couple of posts beneath this one.)