Since the two-child policy was implemented, many of my female friends and sisters-in-law have joined the ranks of older mothers.
Many celebrities in the entertainment industry have also announced the good news of having a second child at an advanced age, such as Zhang Ziyi.
There are also many celebrities who had their first child at an advanced age, such as Gao Yuanyuan.
We all know that both babies and mothers are more prone to problems when giving birth, whether at a young age or an older age. These problems can include birth defects, premature birth, and genetic mutations. Once a genetic mutation occurs...
So what caused this?
You probably already knew the answer during those years when you were at the "peak of intelligence"—younger and older women's eggs are more prone to chromosomal abnormalities.
Title: Chromosomal Abnormalities in Human Eggs Can Affect Fertility
But I know some people must have forgotten, so let's review together.
Hey, hey, hey, don't rush off just yet! This isn't some dry theory; there are actually a lot of interesting things involved!
The innate differences between men and women, besides sexual characteristics, are also reflected in the formation of reproductive cells: males do not form sperm before puberty, but females are born with all the eggs in their ovaries, and these eggs do not begin to mature until the female has her first menstruation.
Are there differences in eggs at different ages?
Of course there are, otherwise why would I have said so much?
Recently, Professor Eva Hoffmann, head of research at the Department of Cellular and Molecular Medicine at the University of Copenhagen in Denmark, led a research team to examine more than 3,000 eggs from women aged 9 to 43. They found that the chromosomes in the eggs of younger women (under 20 years old) and older women (over 35 years old) are more prone to abnormalities, which can lead to genomic imbalances and miscarriage.
What causes this chromosomal abnormality?
When an egg is in a dormant state, a type of molecular glue in the body holds the chromosomes together. When the egg matures, the chromosomes divide.
Because a young girl's eggs are not fully developed, younger girls are more prone to chromosomal abnormalities in their eggs, which can lead to miscarriage or the birth of a baby with a congenital disease.
Intellectually disabled girl sexually assaulted
During this period, there was also a case of a "12-year-old intellectually disabled girl who was sexually assaulted and became pregnant twice." If a child of this age becomes pregnant, she will basically have to have an abortion.
Even one miscarriage is incredibly damaging to an adult woman, let alone two pregnancies in this young girl. The whole incident is chilling and infuriating.
As girls leave puberty, these abnormalities in chromosome division gradually disappear, resulting in healthier eggs.
This condition can persist until one's mid-twenties, but other chromosomal abnormalities may occur afterward.
As women age, the molecular glue is more likely to separate prematurely, which can lead to abnormal chromosome division in immature eggs.
This explains why older mothers are more likely to give birth to babies with congenital diseases.
But why does the human body have this mechanism?
Our close relatives, chimpanzees, have never experienced this situation.
Scientists don't know why human fertility rates rise, peak, or decline within a certain age range.
Professor Eva believes this may be due to the fact that humans have developed two self-protection mechanisms during evolution: one for young girls and the other for older women.
One mechanism protects young women from becoming pregnant until their bodies are fully developed.
At this time, a wider pelvis in a woman's body can reduce the risks of childbirth, thus enabling her to give birth more easily.
However, in my opinion, this "protection mechanism" doesn't seem very reliable. Just like the 12-year-old girl mentioned earlier, the risks of giving birth at this age are not small.
Another mechanism is called the "grandmother hypothesis".
The grandmother hypothesis suggests that the reason humans live longer than adult apes is that postmenopausal women can shift their energy to raising grandchildren, thus improving the adaptability of offspring and promoting genetic optimization. (Great, I'm different from monkeys!)
Grandmother hypothesis
In 1997, this hypothesis was formally proposed by anthropologists Christian Hawkes and James O'Connell from the University of Utah, and anthropologist Nicholas Blurton Jones from UCLA.
During their time living in Tanzania, they observed that elderly Hadza women, after menopause, spent their days collecting food to feed their grandchildren.
However, apart from humans, other mammals begin to forage for themselves after weaning.
Years later, Hawkes and her colleagues studied the problem, and computer simulations showed that, without making any assumptions about the size of the human brain, if grandmothers fed animals, animals that originally had lifespans similar to chimpanzees would have evolved to have lifespans similar to humans in less than 60,000 years.
Furthermore, starting from adulthood, the computer-simulated creature lived like a chimpanzee for 25 years.
However, after 24,000 to 60,000 years of evolution in which grandmothers cared for their grandchildren, the organisms that reached adulthood lived for another 49 years.
The "grandmother hypothesis" posits that in ancient times, women who became grandmothers were considered long-lived. Women who were unable to conceive after menopause would then help feed their weaned grandchildren, giving their daughters or daughters-in-law more time to have children. As a result, their genes (including longevity genes and genes that influence the timing of menopause) would be passed on to more offspring, who would then have a greater chance of surviving and living long lives.
But gorillas don't exhibit this behavior; they don't care for their grandchildren like humans do, and mothers don't have as much time to give birth.
This explains why female gorillas rarely live past their reproductive age (usually 30-40 years old), while human women typically live for decades beyond their reproductive years.
Following this logic, your ancestors could be said to have "given up" their fertility in order to extend your lifespan.
Cry! All of you, cry!
Eva points out that the new research findings could be used to improve the treatment of long-term infertility and increase public awareness about fertility and miscarriage.
The editor sells chicken soup
While miscarriage is undoubtedly a disheartening experience, a proper understanding of the physiological changes in an egg may help us better understand one thing:
Sometimes miscarriage is actually a natural selection process. It's not because you did anything wrong; it's just that your baby isn't ready to meet you yet.
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