For a long time, having children was a young man’s game. Although ancient records are sparse, researchers have found that for most of human history, women typically conceived their first child in their late teens or early 20s; I stopped having children soon after that..
but, recent decadespeople all over the world, especially wealthy developed countrieshas become boot their family From later to later. Since the 1970s, American women have, on average, delayed the start of parenthood. twenty one to 27; Korean women are Tweaked numbers above 32.As more women have children Fortiesthe average age at which women give birth Any In most high-income countries, a proportion of their children are now over 30 years old or rapidly approaching it.
Rama Singh, an evolutionary biologist at Canada’s McMaster University, believes that if women continue to have children late in life, another fundamental reproductive stage may change. menopause Even later. Its age is now around 50 years old, and some researchers believe this number has remained since the origins of humanity. But in Singh’s view, there are no ironclad biological laws that prevent a woman’s reproductive years from extending far beyond that threshold. He told me that if women decide to continue having children into old age, one day hundreds of thousands of years from now, menopause could theoretically be completely eliminated.
Singh’s perspective is not mainstream in his field. However, changes in human childbearing behavior are not the only reason why menopause progresses. Humans are now living longer overall and in some ways healthier than our ancient ancestors. And especially in the past few decades, researchers have made technological leaps that have allowed them to study how people’s bodies function and age in ways never before possible. All of these factors can combine to change the timeline of menopause. This is a grand experiment in human reproduction, and scientists don’t yet know what the outcome will be.
So far, scientists have little evidence that the age at the onset of menopause is starting to change.just a little the studyIt mainly tracks trends over the past few decades, noting changes that can be seen in women around the world over the course of a year or two. some western countriesinclude America and Finland. But Singh thinks it may just be the beginning. Menopause can occur at any age from her 30s to her 60s, but the timing is: greatly influenced by genetics. This change suggests that there is room for evolution. Megan Arnott, an anthropologist at University College London, said if older parents continued to have healthy children, “the age of menopause could be delayed.”
Shin’s idea is based on the premise that menopause is not necessary for humans, or any animal for that matter, to survive. And if the main goal of a species is to perpetuate itself, a lifespan that significantly exceeds reproductive capacity seems contradictory. Researchers have found only a handful of other organisms have long post-reproductive lifespans. 5 species of toothed whales,plus A single population of wild chimpanzees. However, a woman consistently spends one-third to half of her life in menopause, the most documented of any mammal.
In humans, menopause occurs when the ovaries contain fewer than about 1,000 eggs, at which point ovulation stops and hormone levels throughout the body, such as estrogen, plummet. However, there is no biological necessity for a woman’s fertility to disappear after 50 years of life. Each human female is born with approximately 1 million to 2 million eggs in her clutches.comparable What researchers have Estimation in elephantThey remain fertile even into their 60s and 70s. Animal eggs also don’t seem to have a built-in expiration date. For example, it has been recorded that certain whales have given birth to offspring. over 100 years old.
This disconnect has led some researchers to conclude that menopause is an unfortunate evolutionary accident. Perhaps, as some have argued, menopause is a byproduct of long lifespans evolving rapidly and the ovaries not keeping up. However, for most of human history, many women survived well past menopause.Singh argues that menopause is a side effect of men. prefers to mate with younger women, allowing fertility-impairing mutations to accumulate in older women. (If a woman was only looking for a young man, he told me, male Others disagree with this. Arnott told me that if anything, many of today’s men may prefer younger women. because Fertility does not decline with age, rather the opposite is true.
But there is overwhelming evidence that menopause is beneficial for evolved species, including ours, said Francisco Ubeda de Torres, a mathematical biologist at Royal Holloway, University of London. Indeed, menopause is so important that it appears to have occurred multiple times, with whales alone having had it at least four times, Samuel Ellis, a biologist at the University of Exeter, told me.
One of the most prominent and well-supported ideas about why rotates around become a grandmother. Perhaps menopause evolved to relieve older women of the burden of fertility, freeing up their time and energy to help their own offspring raise their poor children. yeah. In humans around the world, grandmother cooperation clearly facilitates the survival of younger generations. The same seems to apply to killer whales. other toothed whales. Kristen Hawks, an anthropologist at the University of Utah, argues that the influence of menopausal grandmothers: very huge That it helped our brains grow bigger and shaped the family structures that still dominate modern society. That’s right, she told me, enough Explains human menopause and what makes us the people we are today.
Some researchers suspect that menopause may be a factor. Other benefits. Kevin Langergraber, an ecologist at Arizona State University, points out that certain populations of chimpanzees can survive well past menopause, despite not actually being grandmothers at all.Chimpanzees and other animalshe told me that menopause may help reduce competition for resources between mothers and children as they try to raise young offspring at the same time.
Whatever the exact reason, menopause can be so ingrained in our blood that it can be difficult to adjust or reverse. Michael Kant, an evolutionary biologist at the University of Exeter, has lived his entire life by ending ovulation early, but says he is the “only master time giver” that can be turned on to simply prolong fertility in human women. The switch told me there probably wouldn’t be one. .
But perhaps the menopause timeline can still vary within generations rather than on the scale of hundreds of thousands of years. For example, malnutrition and smoking are associated with early termination of menstruation. use of contraception May push up the age at which menopause begins return— because these factors can affect your hormones.Menopausal disorders are also more likely to occur happens early Among women of lower socio-economic status and less education. Therefore, simple interventions to improve childhood nutrition may be sufficient to increase the average time of onset of menopause. in certain parts of the worldLynette Siebert, an anthropologist at the University of Massachusetts Amherst, told me:
Such changes are likely to work primarily at the margins, perhaps closing some of the gap between poorer and richer countries. May last up to 5 years.Experts say larger changes will likely require medical innovations that could slow, stop or even go backwards Prevents premature aging of the ovaries and maintains previous levels of estrogen and other reproductive hormones. Kara Goldman, an obstetrician-gynecologist and reproductive scientist at Northwestern University, tells me that one of the keys to rejuvenating your ovarian fountains may be to find a drug that: Ta. Preserve structures that house immature eggs in A kind of hibernation initial state. Some researchers are hoping that this will rejuvenate the tissue that keeps eggs healthy.Still others Generating cells and hormones in the lab Aging women’s bodies are trying to replace what they naturally lose.Dina Emera, an evolutionary geneticist at the Buck Institute on Aging in California, thinks some of the best inspiration may come from species that maintain fertility. very later in life. For example, the bowhead whale can breed even when he is over 100 years old. Looks like it won’t succumb to cancer. Perhaps they are especially good at repairing DNA damage in germ and non-germ cells, Emera said.
While some women may welcome the longer time between childbearing options, Goldman and Emera are most focused on minimizing the health costs of menopause. Studies have repeatedly linked the decline in hormone levels associated with menopause with poor bone health. Some studies also point to cardiovascular and cognitive problems. After menopause, symptoms such as hot flashes, urinary incontinence, vaginal dryness, insomnia, and decreased sex drive may persist for many years. Postponing all of this, perhaps indefinitely, could extend the period during which women can live healthy lives supported by reproductive hormones.
Stephanie Fabion, director of the Mayo Clinic Center for Women’s Health, said extending the lifespan of the ovaries does not necessarily reverse or lessen the undesirable effects of menopause. Additionally, there may be additional risks associated with later pregnancy. It may also increase a woman’s chance of developing breast and uterine cancer, blood clots and stroke, said endocrinologist Jerilyn Prior of the University of British Columbia. Postponing menopause also means a longer period of menstruation and birth control, which is likely to cause many women to stop, says Nanette, an obstetrician-gynecologist and reproductive scientist at the University of Colorado School of Medicine. Santoro says.
But some researchers think it’s worth trying some adjustments. Goldman said that even if menopause once contributed to human survival, it is still “hard to imagine.” Evolution may have resulted in strange inconsistencies in the lifespans of ovaries and other organs that coexist with them. But it also gave us the smarts to potentially break through those limitations.
