Analysis of the dynamics of the male-to-female ratio and interpretation of common knowledge about men's health

What is the ratio of women to men? If we only look at the number of couples in society, we might assume a 1:1 ratio. However, large-scale surveys reveal that the number of men and women is not equal, but slightly different. Statistics show that there were 5 billion people on our planet in 1986. According to UN projections, this number will reach 6.119 billion by 2000. The proportion of men was 50.1% in 1980, 50.2% in 1990, and 50.3% in 2000. my country's fourth national census in 1990 showed that men accounted for 51.6% and women for 48.4%. Overall, the male-to-female ratio appears relatively balanced. However, further analysis across different age groups reveals an imbalance in the number of men and women.

To understand the male-to-female ratio and its changes, we must start with reproductive cells. The fertilized egg formed by the union of sperm (XY) and egg (XX) results in either a male (XY) or a female (XX) offspring. The primary sex ratio in humans is 120-150 males to 100 females. This means that for every 100 female fetuses formed at conception, 120-150 male fetuses are simultaneously formed, significantly exceeding the number of female fetuses. Why does this happen? We know that only one egg matures in a woman's ovary each month. To fertilize this single egg, millions of sperm compete in a drop of semen. The weaker, less viable sperm fall behind and perish along the way; only the more viable sperm can approach the egg. Of the many "strong" sperm that approach the egg, only one will fertilize it. As mentioned earlier, because Y-type sperm are more mobile and have smaller, pointed heads, they have a greater chance of fertilizing the egg than X-type sperm. This may be one reason why there are more male than female fetuses.

The ratio of males to females at birth is called the secondary sex ratio. The secondary sex ratio in humans is approximately 106:100; that is, for every 100 female infants born, 106 male infants are born simultaneously, with more male infants than female infants. The male-to-female ratio is almost 3:2 during the embryonic stage, but decreases significantly at birth, mainly due to a higher rate of male abortions than female abortions. Statistics show that, excluding early abortions within three months, for every 100 female fetuses aborted, 160-170 male fetuses aborted. Furthermore, early abortions (before two months) are 7-8 times more common in males than females. In many cases, the conception of a "boy" fetus is terminated during the embryonic stage, even before the pregnant woman suspects she is pregnant. It can be said that male fetuses are less viable than female fetuses in the womb.

Male fetuses not only have a higher mortality rate in the womb, but also a higher mortality rate after birth. According to Swedish statistics in 1974, the first-year mortality rate for male infants exceeded that for female infants by 24.3%. During the 1-4 year age range, the male mortality rate exceeded the female mortality rate by 27.2%. Between the 15-24 year age range, the male mortality rate was twice that of the female. The sex ratio varied at different stages thereafter, but the overall trend was a continued decline in the male-to-female ratio. Interestingly, however, at the marriageable and reproductive age (approximately 20-40 years old), the sex ratio was roughly 1:1, ensuring that almost every man and woman could find a spouse.

Overall, the average lifespan of both men and women has been steadily increasing. According to Soviet statistics, the number of elderly women of all ages was, on average, 2.5 times that of men of the same age. Their 1970 registrations showed that among those aged 80 and over, the number of women was 2.7 times that of men. Statistical data shows that from conception to death, the male-to-female ratio gradually decreases; the ratio changes from greater than 1 to much less than 1, and from more men than women to women far exceeding men. This evolutionary process illustrates that, regardless of the stage of growth and development, the survival rate of women is far higher than that of men.

People are accustomed to viewing men (males) as the stronger of humans (animals), but judging from the evolution of the sex ratio, the true stronger are women (females), not men.

The human male-to-female ratio is roughly equal. The same is true for other organisms. Nature's balance is remarkable, always maintaining a certain degree of equilibrium between males and females, which is beneficial for reproduction. However, some organisms exhibit rather cruel behavior in maintaining this balance. For example, as soon as a male scorpion impregnates a female scorpion, the female kills and eats him. The same is true for female praying mantises. The female praying mantis's cruelty towards her mate is arguably the worst among animals. She is about 10cm long, very beautiful, with a slender and elegant figure. Her emerald green body is covered with several light, gauze-like wings, and her long neck supports a head that can turn freely. Her large, crystal-clear eyes give her a serene and charming appearance. But who could have guessed that behind this charm lies a ruthless and murderous intent? In the early stages of mating, the male praying mantis frolics to win the female's favor. During mating, the female turns her head and uses her toothed, guillotine-like forelegs to embrace the male's head, as if kissing her beloved husband. In this tight embrace and "kiss," the husband's head disappears. It turns out the bride wasn't kissing, but rather biting and chewing on her husband's head until only a few wings remained. To continue their lineage, the poor husband not only offered no resistance while his wife devoured him, but even as little of his body remained, he clung tightly to her, fulfilling his duty of procreation—a truly moving sight.