Mothers and Matriarchs
Mammals and Menopause
(Why I’m not dead yet!)
Menopause never used to be openly discussed. If mentioned at all it was is hushed voices between women of a certain age.
But currently the voices of peri- and post-menopausal women are being heard and society is being asked to acknowledge the huge changes faced by people with female biology.
Yet, even now, the reason humans experience this transitional period between fertility and old age is not really addressed. Which it should be.
Now, this is not the article I thought I was writing! It turned out to be quite the rabbit hole as I discovered why!
menopause (noun)
The ceasing of menstruation.
The period of a woman’s life (typically between the ages of 45 and 50) when menstruation ceases
Not all mammals experience menopause. Indeed the vast majority do not. The typical cycle is childhood, fertility and death. When a female can no longer produce young, she no longer has a purpose.
Science is still learning which species do go through a period of menopause and continue to live. Those who do tend to share these traits:
Intelligence
Community
Skills
Basically, it takes big brains to have a reason to live beyond reproduction.
Until 2023, it was understood humans stood alongside these menopausal elders in nature:
Toothed Whales - orca, narwhal, beluga and pilot whales
Seriously, that was it! And these mammals don’t even menstruate in the way humans do. So is it even menopause we share?
Then researchers studying the Ngogo chimpanzee group in Uganda identified something not seen in wild chimpanzees before:
“When Sholly Gunter started working with the apes in the early 2000s, she noticed this right away. “We had a lot of old ladies,” she says, “and that was unusual.””
By collecting urine samples for the apes and analysing them for hormone levels, they confirmed that this community of chimpanzee were reaching menopause around 50 years of age and living a life-stage beyond that.
This evidence has, of course, created more questions than it answers!
“Not all chimpanzees appear to undergo menopause—but this could be a result of factors other than biology. In most populations of chimps outside of the Ngogo group, adult females live to around age 30, usually because of predators, disease or stress. Alberts says the new paper’s results are so robust that she can’t argue with them, however. The next step, she adds, would be to do similar long-term studies in additional wild chimpanzee populations to figure out whether the Ngogo chimps are unique in living beyond their reproductive years.”
Humans and chimpanzees experience menstruation and expel the lining of the uterus when eggs are not fertilised. This unique process is not standard in other mammals who reabsorb these tissues. So if menopause refers to an end of menstruation, it stands to reason most mammals don't experience it.
(Which animals “overtly” menstruate like humans and chimpanzees. Some Old World monkeys, a few bats and the elephant shrew have less-overt menstruation. Some other mammals bleed when in oestrus, signaling they are ready for mating but that is a different process.)
At this stage, both menstruation and menopause are starting to look like some random lucky dip by Nature!
The End of Fertility
What mammals typically reach is the delightfully named oopause. This refers to the time when the ovaries cease releasing eggs, meaning the complete end of fertility. However, the period of time between oopause and end of life is usually short. Only in captivity is an extended period of post-fertility seen. Probably because aging captive animals are fed and medically cared for as they age.
In modern-day humans, the term oopause is generally used in the context of poor ovarian activity requiring fertility treatment. It is the time before menopause when women trying to conceive have very little chance of doing so without assistance.
However, there is opinion that the term oopause might be a more accurate description of this lifestage in human females. All mammals reach oopause, not all reach menopause. And oopause is reached before the end of menstruation. Most human females become fertile in their teens, with peak fertility in their twenties and gradual decline in the thirties.
The age of women at the birth of their first child is steadily increasing, narrowing the gap between it and oopause. By 35, fertility begins to significantly decline and by 45, women are unlikely to concieve naturally.
Menopause and Grandmothers
The Grandmother Hypothesis considers one reason for humans to live beyond their fertility. And it is because we are human! As discussed, human infants are born noticeably premature developmentaly compared to other mammals. This means an intensive level of care is required in infancy (0-3years) leaving little time for much else. However the 4-8 year old is far from independent and still needs food, shelter and security. As typical natural child-spacing is around 3-4 years, this means competing needs for maternal support between the newborn and the young child. And there enters the grandmother. No longer needing to care for babies of their own, elder women can focus on gathering food for the young children and teaching them skills they will need to become independent. A grandmother can watch over several young children while her daughters care for their infants and toddlers more exclusively. A heavily pregnant mother of a 3 or 4 year old can rest and nourish herself in preparation for the birth with the support of a grandmother who increasingly cares for the newly-weaned child.
Grandmothers will cosleep alongside the older child and nurture them in the day and night. Grandmothers form part of a cooperative community practice called alloparenting. All females within a group will share the care of infants and young children, with babies and toddlers being held and carried by multiple kin throughout the day, returning to the mother for frequent breastfeeds. Children as young as four take part in alloparenting, holding and carrying babies. By the time they become parents, they are skilled in meeting the needs of babies.
Menopause brings an end to the female human’s reproduction but not her life. From an anthropological perspective, young women would have their first child in their late teens and have a new baby every three or four years until their fertility begins decreasing in their thirties and eventually reach oopause between 35-45, followed by menopause around 45-55. The iKung people of the Kalahari in Africa average 44 months between births and typically have 4.7 live births. The key to this child-spacing is the frequency of breastfeeding - in 15 minute observation periods of children under two years, only 25% of elapsed without a nursing session! Children under three woke at least once a night to breastfeed. This frequent breastfeeding suppresses fertility.
Although women in modern western society experience menstruation for most of their fertile years, mounting up to decades of monthly bleeding, this is not the biologically typical pattern. In women living traditional lifestyles of near-constant breastfeeding in the first two years of each child’s life and a gradual weaning across the following year or two, menstruation and ovulation would be mostly suppressed with a brief return before another conception. A woman birthing a baby every five years between 15 and 35 might only experience half a dozen menstrual bleeds in that time, signaling a return to fertility.
Beyond menopause she would be able to support her daughter in those years raising babies and then be cared for, in turn, in her later years until end of life.
Both human and chimpanzee live in similar social groups, as do some other primates. A troop or band of females live with an alpha male and younger, submissive males. Mating can occur between the females and any male within the group, meaning males do not know which offspring might be theirs, so they offer protection to all.
Chimpanzee societies are made up of multiple family groups living together with as many as 120 individuals or as few as 20. These communities might come together regularly but also spend time in their smaller family groups. In the wild, chimpanzees mostly give birth every five years. Infants usually wean around this age but remain close to their mother. Chimpanzees learn from each other and pass on knowledge of using tools like rocks and sticks to access food. Adult males will feed and care for their mothers in old age as a mark of respect. While they do not know who has fathered them, the mother-child bond remains strong.
In chimpanzee and human society, it is the daughters who tend to move away from their mothers. The grandmother within the group is typically the mother of the male in the community. She is heavily invested in her son’s off-spring surviving infancy and childhood. Menopause allows her to focus on the survival of a new generation born to younger females rather than continuing to breed with her own aging body. And this might be a clue into the reason these females outlive their fertility.
Remember those toothed whales?
A distinction between human and chimpanzee females and those of the toothed whale elders is this connection with their sons. And this is also when we need to consider the elephant in the room - the actual elephants, as it happens!
African and Asian elephants do not appear to experience menopause and remain fertile well into their senior years. Which doesn’t seem to make sense if we look back to those original qualities of intelligence, community and skills. Until we look at their societal structure.
Elephants are matriarchal societies. They are led by a senior female, whose daughters, granddaughters, sisters and nieces remain within the family group for life. It is the males who leave, the sons and nephews moving into groups of juvenile males, and senior males living solitary lives. Females can continue breeding because they are unlikely to mate multiple times with the same males. In fact, male African Elephants only begin mating at age 40 and 75% of them die without fathering any young. Those who live to later life become very high-ranking and father many calves.
Whales have a different family structure again! Both sons and daughters continue to live in with their mother and the senior female supports both with her skills and knowledge. Like elephants, these elder females lead their nomadic family groups as they travel with the seasons. But while elephants are gentle vegetarians, toothed whales are carnivores and work together to hunt their prey. And this is where the wisdom of the elder females pays dividends. Without ongoing fertility, she can use her knowledge and skills to teach younger members of her family and also support her daughters while they are nursing and caring for their young.
There are still so many questions though! Dolphins do not experience this extended life-stage following the end of fertility. Orangutan, who live and raise their young alone, do not live long after the end of fertility. Neither do gorilla, who live in groups like humans and chimpanzees.
A word about grandfathers
What about the role of male elders, you might be wondering? In societies like humans and chimpanzees, the senior males have significance in hunting for meat and protecting the groups territory. For as long as he can physically keep up with the fast-moving group, his wisdom will guide them. But as age catches up, the older males will retire and instead stay with the females and their young. Offering a protective role, they also play with the babies and teach the younger children skills with tools. These grandfathers are revered for their contributions and are cared for as they approach the end of life. Both grandmothers and grandfathers are important within their communities.
