Comment by derektank
3 days ago
Not really, the reason so many sperm are needed is because a woman's reproductive tract requires an aggressive immunological response to foreign bodies (which sperm are). The vagina provides a direct route for pathogens through the cervix and uterus to the fallopian tubes (which can be scarred by inflammation resulting in infertility) and they themselves open up directly into the peritoneal cavity (potentially exposing a woman to septic shock or death if an infection reaches it). To protect against that, the vaginal environment is highly acidic, has layers of mucus that shields the cervix, and a high concentration of immune cells proliferate throughout. Men need to produce so many sperm because they need to be able to temporarily overwhelm these defenses.
What you say is right, but it does not contradict the parent poster.
Both reasons for the high count of sperm cells are true.
There must be many sperm cells to survive the adverse conditions, but there is also intense competition with the sibling sperm cells.
The DNA of the sperm cells is generated by a random generator, which is the meiosis mechanism, which randomly shuffles then randomly discards half of the father DNA.
The sperm competition then discards the random choices that happened to be bad, implementing an optimum search algorithm.
The sperm competition is only a first filter for rejecting bad random choices. Many embryos will die very soon, without ever developing, rejecting other bad random choices.
>The sperm competition then discards the random choices that happened to be bad, implementing an optimum search algorithm.
Only a very small percentage of sperm (less than 5%) are chromosomally abnormal. Meanwhile, the vast majority of sperm are morphologically abnormal in some way. So there's not really a tight relationship between genetic problems and sperm fitness. Men with infertility due to low motility, for example, are capable of having perfectly healthy children with those low motility sperm through IVF.
>The DNA of the sperm cells is generated by a random generator, which is the meiosis mechanism, which randomly shuffles then randomly discards half of the father DNA.
Meiosis also occurs in women (technically in the female fetus), but women generally produce only a single egg each ovulation.
>Many embryos will die very soon, without ever developing, rejecting other bad random choices.
A very large number of zygotes/blastocysts survive until implantation, upwards of 50%. And of those that do, maybe 20-40% are miscarried before 12 weeks. All things considered, about 1 in every 4 fertilized eggs results in a successful pregnancy.
So yes, it's absolutely true that the body filters out chromosomally abnormal germ cells and zygotes. But an egg is orders of magnitude more likely to survive than a sperm (even if you take into account the eggs that die in the uterus without being released). And the overwhelming reason is that the egg is simply in a much less hostile immune environment.
> So yes, it's absolutely true that the body filters out chromosomally abnormal germ cells and zygotes.
> A very large number of zygotes/blastocysts survive until implantation, upwards of 50%. And of those that do, maybe 20-40% are miscarried before 12 weeks.
That’s with sperm going to a filter process for genetic abnormalities before fertilization. If hypothetically 5% fewer zygotes survived that would have real consequences not just for humans but in terms of increasing variability in litter sizes for mammals with multiple births etc.
as to the large number of sperm required, it is note worthy that excess male germ cell's is the norm for many?, most?, all?, species, and that in a lot of cases there is a number of complications involved in transfering them to a female, and altogether improbable solutions, also the basic mechanisms for germ cells are conserved by plants and animals, "pollen" bieng tailess sperm.....except in the case of ginko trees, that have motile sperm so the real questions are around why did evolution produce, and stick to this mechanism, and not so much about our species rather mundane take on it.
Mosses and ferns also have motile, flagellated reproductive cells.
You are all wrong :)
There is a competition between sperm from different males.