Now, the actual study was NOT discredited, for the simple reason the researchers said the comparison between what they did in 1990 to what had been done in 1940 was irrelevant (fun but irrelevant). The reason for this was simple, the 1940 study sample group were from New York City, the 1990 sample group was from all around the world. Thus the first problem, different sample groups.
A second problem is men naturally produce more sperm in the presence of other men. The more men a man is around the more sperm he will produce. The less men, less sperm. New York City in 1940 was a density populated urban area, lots of men, so sperm counts would be high. In the 1990 study, men were NOT only from large cities but also from rural areas. Less men an man interacts with, less sperm he produces.
In simple terms the 1990 study was an attempt to get a base for future study not for comparison with the 1940 test. A comparison was made, and it made headlines but the comparison was irrelevant.
Now as to this study, the actual report contains the following clauses, given that this is over a 17 year period and the decline is constant, could be valid, but given that we have NO IDEA where the men live AND it is part of a study involving infertile women who want to get pregnant, it could be that we are seeing a growing number of men being tested who live further and further from the urban areas of France.
SUMMARY ANSWER Among a sample of 26 609 partners of totally infertile women undergoing an assisted reproductive technology (ART) procedures in the whole of France over a 17-year period, there was a continuous decrease in semen concentration of about 1.9% per year and a significant decrease in the percentage with morphologically normal forms but no global trend for motility.
LIMITATIONS, REASONS FOR CAUTION Socioeconomic status could not be controlled for. Despite universal access to medical services in France, couples undergoing ART are expected to have a higher educational level on average compared with those of the general population. Therefore, the real values in the general population could be slightly lower than those presented and the decrease possibly stronger, as the population study is less likely to smoke or be overweight, two factors known to impair semen quality.
:http://humrep.oxfordjournals.org/content/early/2012/12/02/humrep.des415.short?rss=1
http://humrep.oxfordjournals.org/
Men have some of the largest testicles to body size among Mammals. Under present theory, when Chimpanzee and Humans were still one species, the species evolved to live in a group. This was a all male relative group (Chimpanzee still live is such groups). It is the female, who on puberty, leave the group and look to join another group. Given that any female would attract all of the males in the band if she was in heat, but the males had evolved NOT to fight each other for the right to have sex with that female. these proto Chimpanzee/Humans ended up competing on the sperm level. Male proto Chimpanzee/Humans slowly evolve bigger testicles so they could produce more sperm so to have a better chance of getting the female pregnant then the other males who had access to her. Thus these proto Chimpanzee/Humans testicles slowly became larger, much larger then other primates, even the bigger Gorillas.
These Proto Chimpanzee/Humans also evolved three types of sperm, the classic sperm to swim to the ova and get the female pregnant, then two other types of sperm. The first is a blocking Sperm, its forms a barrier to prevent sperms from other males from passing through. It will permit sperm from the same male to pass through but not other males. The third type is a killer Sperm, it kills sperm from other males. This all had to do with competing at the sperm level.
Sometime after Chimpanzee and Humans evolution diverged, human evolved to have sex primarily with their mate. The pair bonding is what separates humans from the Chimpanzee when it comes to actual sex within the species. When human evolved to make the pair bond their primary means of reproduction, the need to evolve larger testicles died out. Men were NO longer competing at the sperm level, we had evolve to compete at the pair-bond level.
On the other hand Chimpanzee continue to compete at the sperm level, thus Chimpanzee have testicles almost twice as large as a humans. At the same time males have had no advantage if their testicles grew smaller thus testicles are believed to have stayed about the same size since the pair bond evolved.
I bring this up, for men produce a huge excess of sperm, thus a drop in sperm i not that big a deal. Given the background that the ancestors of Modern Humans once had to compete at the sperm level we still retain much of the hardware to do such competition, such as an increase in sperm count as we come in contact with more males (and less sperm count as the number of males we come in contact with drops).
Given this background, the lack of social economic background and where the men lived (and how that changed in the 17 year period) permits a big hole in this study, just like the earlier study. Where a male lives and how many males he lives near seems to be a factor in Sperm Counts and thus without that data this study is almost worthless. Actual Sperm count may be down, it may be up for some reason other then interaction with other males, but to have a valid study on sperm count, the fact it varies depending on how many males a males comes in contract with, knowing that factor is important for this data to be any good, except as a joke on the late night circuit.
Another factor for the drop in sperm count can be seen in the following report:
He found that the volume of sperm a man ejaculates while having sex with his partner is unrelated to how long it has been since he last had an ejaculation; the important variable is the length of time that has passed since he last had sex with his wife. The volume of sperm may be as much as three times that of normal if the man has been separated from his wife for a long period of time. If the men were in proximity of their wives during a similar period and were sexually abstinent, their subsequent ejaculate did not show the same rise in volume.
http://www.ulm.edu/~palmer/SpermWars.htm
http://www.ulm.edu/~palmer/SpermWars.htm
Remember since 1989, the Cold War ended, and every country in Europe has reduced the size of its military, thus you have less men spending a month on maneuvers and coming home to their wives then you had in 1989. This drop has been gradual. In 1996 the French Government said it wanted to reduce the size of the Army and end the draft by 2002, they ended it in 2001. During the same time period, to make the army more appealingly, separating men in the army from their families for training was reduced starting in 1989 and continues to this day. Thus the fact that men in Europe (and thus France) are no longer subject to one month of active duty then 11 months "on leave". (referring to an old joke about men in Europe from the 1870s to 1990s, the men were all in the military, except when on leave 11 months of the year).
On France and the Draft:
http://www.checkpoint-online.ch/checkpoint/j9/j9-0002-francedraftdemocracy.html
Through Sperm Competition has been criticized:
http://www.seductionlabs.org/2007/05/24/sperm-competition-and-the-kamikaze-sperm-hypothesis/
I suspect the critics have a problem, when did sperm competition ends for Humans? i,e, when did Humans embrace the pair-bond? With the pair bond you no longer had sperm competition.
I like the comment about testicles size, gorillas are small, Humans are larger, but Chimp beat Human out of a huge amount. While Chimps have bigger testicles the Humans, Human Males have longer penises (3 inches for chimp, 5 inches for men, Gorillas penis is only 1 1/2 inches long full erect).
= new reply since forum marked as read
