Every time an egg is fertilized, only one sperm is successfully fertilized, which means that the other tens or hundreds of millions of sperm are useless. So why does the success of egg fertilization also depend on the number of sperm rather than sperm motility? The reason is that the sperm that eventually fertilizes the egg is usually not the strongest sperm, but the luckiest sperm. Let’s take a look at the life and death journey of the sperm. First, the sperm is wrapped in semen (seminal plasma) and ejaculated. Ejaculation is a high-risk event. Imagine, as it were, thousands of people slipping down one piece on one of those super-high slides at a water park, which would surely lead to a …… stampede! Although sperm are a bit tougher than living people, at least they won’t break any bones or anything (although ding dongs can break bones), there are a series of accidents that can happen in the meantime. For example …… Sperm’s tail is ripped off – death! Sperm gets shot outside – death! Several sperm’s tails get entangled – everyone hugs and dies! Death has nothing to do with being strong, even if the sperm are strong, they can’t withstand the flood of semen! Well, even if the sperm were good and escaped the stampede, there’s still a second hurdle. You know, a woman’s immune cells are free to come and go as they please in the vagina (this is the basic principle of sexual transmission of AIDS), and in the eyes of these immune cells, there are only two kinds of things in the world: their own cells and other things that must die. Well, sperm is something else …… Eh, this actually can not be helped ah, the vagina is a warm and moist and dark and not very good cleaning place, is a bacterial breeding paradise, not in the immunity of a little more ruthless, the human race is going to be extinct said. It doesn’t matter, the sperm swims fast (it really swims fast, I won’t tell you that I chased the sperm all over the field of view when I did the monosperm injection ……), so if you can’t beat it, you can run away. That’s true, but …… sperm are blind! So in reality, sperms are just swimming around in the vagina, and if you’re lucky, they might just make it to the cervix, but if you’re not, they might just turn around and get wiped out by white blood cells. So the vagina is a slaughterhouse! Worse than paper towels, eh. Like this …… Of course, even if the escape is successful, if you escape when you go too much wrong way also does not work, because the sperm stored energy is more limited, and …… wrong way to go too much if you are too far behind too much, even if you stick to the end of the line is also not much sense. This story tells us that roadkill has no future …… Well, if the sperm is really good to burst, did not take too many wrong way through the cervix, into the uterus, the sperm’s luck is finally going to be a little bit better, because the human uterus is very small, do not need to use a lot of effort to pass, if replaced by the mouse’s uterus, that still have to die a large number of people. This is the human uterus This is the mouse uterus, compare the length of the uterus (those two pods like are the uterus yo, mice have two uterus yo ~) The reason why the human uterus is so small is because human beings usually give birth to only one at a time, so the inside can hold a fetus on the good, while the mouse can give birth to 20 or 30 at a time …… But, after the uterus and will die half of the sperm, because although humans do not have two uteruses, but there are two fallopian tubes, and even the woman herself does not know which fallopian tube the egg is in, so the sperm has to go which way, only by …… guessing! Because the fallopian tubes have no way back to go (there is a way back is not much use ……), so this level will again kill a bunch of bad character as well as have a choice phobia (fog) sperm. When you get to the fallopian tube, you finally get to the egg (forget about the ones that died in the fallopian tube and lost their way), and the sperm have to welcome their big boss, the egg! That’s right, the egg! Because outside the egg there is a layer of extremely dense structure, called the zona pellucida (in fact, outside the zona pellucida there is also the oocyte, but that a little bit of obstruction is basically negligible, at most can only kill 70% or 80% of the sperm, basically negligible ~) This zona pellucida is a bug in general existence, why do you say so? Because the sperm can use its “head” (the acrosome) to dissolve the zona pellucida, creating a hole in the zona pellucida for the sperm to pass through. However, one sperm is not enough to dissolve through the zona pellucida!!!! It takes many, many sperm to “work together” to dissolve the zona pellucida, and as soon as one sperm passes through the zona pellucida, the zona pellucida quickly closes up, preventing any other sperm from re-entering. So the sperm that finally combines with the egg does not necessarily have to be the strongest, but the one that is in the right place at the right time when the zona pellucida is about to be dissolved through is just the right one to make up for it! As you can see, the sperm so all the way to death, not a little base basically can not afford to spend, and the vast majority of sperm cause of death with the strong godma a little relationship is not, so in the long evolution, the sperm, or males will have to use the sea, ah no, the sea of sperm tactics ~!