According to foreign media reports, why do men and women have different life spans? Usually men who appear to be strong have a shorter life span than women who are weak. Currently, Richard G. Bribiescas, professor of Anthropology, Ecology & Evolutionary Biology at Yale University in the United States, points out that the difference in life span between men and women is closely related to the testosterone hormone index.
Bribiskas said, "Years ago, when I was conducting doctoral research on the history of human evolution in the jungles of South America, I met a man in a remote indigenous tribe. He was wearing an old baseball cap. This hat was probably It was presented by a local missionary, and there was a line written on the hat: "A man will go through three stages in his life: seed, no seed, and extinction (Stud, Dud, Thud)." It's really hard to believe that this experience made him I still remember it. This line summarizes people's life and has a certain warning effect. The hat could probably be purchased at a roadside truck stop for just a few dollars, but perhaps this passage captures the fascination of human science.
It is well known that young men consistently account for a higher proportion of fatalities from traffic accidents and risky behavior than other age groups, especially those in their late teens and early twenties. This is not a good idea for insurance companies. What news or secrets. Indeed, regardless of differences in environment or lifestyle, men do generally die younger than women and are more likely to develop cancer or heart disease at a young age. In fact, for the top 15 causes of death in the United States (attributable to 80% of deaths), men have a significantly higher risk of death than women.
It's clear that evolutionary factors played a role, Brybiska noted. The question, however, is why this is so? Does human evolution naturally favor men, making them live shorter than women? This is undoubtedly a compelling academic question. I am now in my 50s and I have to admit that every new gray hair now adds to my fear of aging.
It turns out that in many species, males tend to have shorter lifespans and higher risks of death. Natural selection does not appear to favor traits associated with health, vitality, and longevity. Instead, it promotes traits that increase reproductive success, or, in evolutionary biology terms, fitness. If increasing fitness comes at the cost of shortening lifespan or harming physical health, then the organism itself will prioritize these traits. In other words, sexual reproduction is more important than extending life span.
"Masculinity keeps you from living as long as women," says a Yale University evolutionary biologist.
The trade-off between longevity and reproduction is evident in the female body—pregnancy, childbirth, and breastfeeding all drain the body and energy. The latest research shows that the more children you have, the higher the level of oxidative stress in a woman's body, which in turn will accelerate women's aging after menopause. In 2006, a historic study of rural women in Poland found that the more children a woman had, the shorter her postmenopausal lifespan was. Although more research is needed to confirm, it does appear that "reproductive effort" can shorten your life.
But what will be the impact on men? They obviously do not need to bear the physical wear and tear of pregnancy, but in order to improve the reproductive success rate, men must also allocate a large amount of energy during the reproductive process, and their health will also be affected to a certain extent afterwards. damage. "Reproductive efforts" are reflected in increased risk behaviors and weight gain. The latter is especially manifested in the increase of sexually dimorphic skeletal muscles, such as: extra muscles in shoulders, back, arms, etc. that are unique to men. The energy consumed by men's metabolism to maintain these muscle movements during their lifetime is equivalent to the energy loss of women during pregnancy and lactation. However, the challenges of men's metabolic consumption to health diseases are controllable to a certain extent. After all, in order to balance the conflicting demands of various body functions, men have evolved corresponding physiological mechanisms that are conducive to the continuation of human life. Hormones are one of the most important factors in managing these trade-offs. In men, testosterone regulates muscle and reproductive behavior, but like everything else, such regulation requires some effort. price.
Testosterone is often described as a male hormone. In fact, women also produce testosterone in smaller amounts. In addition to causing beards to grow and the voice to become deeper, testosterone is closely related to energy consumption in men. It is a very important anabolic hormone and has a significant impact on male energy consumption. In other words, male hormones can promote anabolism, or strengthen muscles and accelerate metabolism at the rate at which muscles consume calories. In addition, testosterone can also promote fat burning, increase sexual desire and improve mood. Judging from these factors, testosterone seems to be very beneficial to physical health, but in fact it is a double-edged sword.
Burning fat will make you look better when you look in the mirror, but in a wild living environment, insufficient fat reserves may cause health risks and make you susceptible to viral infections. This is evident in many organisms, with dramatic increases in testosterone levels signaling an increase in "reproductive efforts" but also threatening other physiological needs associated with good health. For example: the Northern Australian quoll (Dasyurus hallucatus) is a medium-sized marsupial. During the lifetime of male Northern Australian quolls, their testosterone levels will experience a significant increase, which arouses their strong desire to mate. , but it also leads to higher mortality, because due to sexual competition and fat loss between males, the lifespan of female northern quolls can reach 3 years, while the longest life span of male northern quolls is only 1 year. As ecologist Jaime Heiniger expressively puts it, "Male quolls seem to mate to death."
The effects of testosterone on human lifespan and aging are subtle and difficult to assess, but because men generally live shorter lives, they are likely to experience something similar to the above. Because it is unethical to experimentally manipulate testosterone in men to determine its effects on lifespan, researchers often must search for more subtle clues in the historical literature. For example: In China and the Ottoman Empire in the late 19th century, certain religious sects would force men to castrate their reproductive organs, removing their entire reproductive organs, including the penis and scrotum. In the pre-industrial era of Korea, eunuchs were common in the royal court; in Europe in the 17th and 18th centuries, castration was also practiced in children's choirs, and there were other cases of castration of reproductive organs. However, the above three cases clearly record the life span of these men. The records of China and the Boy Choir show that eunuchs live longer than uncastrated men; the Korean historical archives show that palace eunuchs live longer than ordinary men.
This being science, even if these studies are consistent in their findings, the evidence provided by these studies is not enough to draw a firm conclusion. Other factors, such as nutritional level, socioeconomic status, may also affect lifespan, but do not Completely affected by the hormone testosterone.
"A man will go through three stages in his life: having a seed, not having a seed, and becoming extinct (Stud, Dud, Thud)."
In order to better understand the specific effects of testosterone, scientists must use "intact" male models as research subjects and observe the changes in the effects of testosterone supplementation in these men. Ornithologists have now shown that experimentally increasing testosterone levels, which often supplement male birds' testosterone levels, enable them to build more nests and fend off competitors than unsupplemented males. and raising more offspring. In addition, some males may exhibit a certain competitive advantage if their testosterone levels are naturally high. If testosterone is so beneficial to reproductive health, then why don’t all male birds maintain such high testosterone levels? This is the theory put forward before - too much testosterone comes at a cost. Although male birds supplemented with testosterone can have strong reproductive ability, their survival rate has decreased. These male birds have a greater loss of body fat and it is difficult for them to survive the breeding season healthily and smoothly.
In addition to birds, in vivo testosterone supplementation is also popular among healthy men, which can also provide insights into the impact of testosterone on "reproductive effort" and lifespan. While it's too early to say that taking testosterone will shorten a man's lifespan, a growing body of evidence is beginning to favor this conclusion. A 2014 study showed that older men taking testosterone were more likely to have an acute, nonfatal myocardial infarction 90 days after their first dose than before treatment. Higher testosterone levels may help with muscle formation, but older men's body organs may not be able to withstand the corresponding metabolic burden. Obviously, we need more research to confirm.
Testosterone hormone not only affects metabolic changes, but also has an important impact on the immune response in men throughout their life. According to Yale University evolutionary biologist Stephen Stearns - "Masculinity keeps you from living as long as women."
Indeed, men are generally more vulnerable than women to fighting off infections, and this difference may be due to a variety of factors. Perhaps it's because men are more exposed to infectious agents than women, or because men are at a chemical disadvantage when it comes to fighting off infectious diseases—a hypothesis for which there is growing evidence. Testosterone suppresses immune function, while estradiol, the predominant estrogen in women, increases immune response. However, estradiol can also increase the risk of autoimmune diseases in women, and although it helps with reproduction, like testosterone, too much in the body still comes at a cost.
In studies of wild bird, reptile, and mammal populations, researchers have found that testosterone impairs immune function, exacerbates infectious diseases, and ultimately leads to death. It's unclear whether testosterone in humans has a similar effect, but testing data collected on men living in areas with high risk of infection confirmed similar trends. A 2005 study conducted by researchers in Honduras showed that men with malaria had lower levels of the hormone testosterone than men without malaria, and that when infected men were treated, testosterone levels returned to levels not seen before. Levels of infection in the male population.
Infections aren't the only thing men have to worry about. Testosterone and other hormones are also linked to a greater risk of cancer, especially when it comes to prostate cancer. For example, people with higher testosterone levels are more likely to develop prostate cancer.
"As one ecologist described it, male quolls mate to death."
So why do men have to suffer the negative effects of testosterone? If we follow Darwin's evolutionary explanation, then the reproductive rewards of male mammals should be much greater than that of female individuals. Mating opportunities are an important factor limiting male fitness. We can assume that if a man mates with 100 women in a year, they may have 100 or more offspring. But this is not the case for women. The prevalence of polygyny in mammals, other primates, and human societies demonstrates the differences in fitness limits between men and women. Women can improve their own fitness by seeking more mating opportunities, not by raising more offspring. Essentially, male mammals prefer to invest in metabolically more costly behaviors using energy-intensive hormones such as testosterone because this significantly increases their own fitness.
For primitive humans who lived in the Pleistocene epoch millions of years ago, the above explanation made some sense. But does this explanation still hold true for today's men? It is possible that although humans are increasingly influenced by culture, it is still difficult for humans to completely escape natural selection, such as trait differences, trait inheritance, and reproductive success. rate etc.
However, this does not mean that men cannot evolve other reproductive strategies. In addition to being prone to risky behaviors and displaying energy-intensive, life-shortening physical characteristics, men have also evolved another form of reproductive effort - "paternity". "paternal investment", a phenomenon that occasionally occurs in primates. In order to promote the evolution of "paternal investment", men must ensure that they are available for their offspring, risk-taking behavior and energy-intensive organization take a backseat, so that men can maintain healthier physical condition and maybe even extend their lifespan appropriately. This means that after becoming a father, taking care of his offspring will cause his own testosterone levels to decrease and his weight will increase, but this kind of "paternal investment" is very beneficial to health.
Bribiskas, a professor of evolutionary biology, pointed out that I doubt whether the theory of natural selection applies to men or humans. Based on the past history of human evolution, we may still have to endure shorter lifespans and poorer health, but the nature of evolution changes over time. By nature, humans are extremely malleable. Physiology that supports plasticity may be the reason why we humans have evolved defining traits: large, energy-hungry brains, longer lifespans, longer childhoods, and more time to raise offspring. This may help explain that there are more than 7 billion people in the world, but in fact these phenomena are strongly supported by reproductive fitness. Men have evolved "paternal care", which may be a novel Reproductive strategies that help them succeed on their evolutionary path. But that doesn't completely change the fact that they still need the hormone testosterone to reproduce, but at the same time they're unlikely to give up the life and health related losses, but that being said, being human is still better than the quoll, despite human evolution It is a road to hell, but we still have to keep going.
