As far as I am aware, female mammals cannot produce eggs (as in ova) after a certain age/maturation.
How could the female produce eggs for an unlimited amount of time, resulting in a 'queen' mammal similar to queen bees?
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asked Mar 13, 2019 at 8:29
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5$\begingroup$ "unlimited amount of time" as in "forever", or as in "when she dies after her species' normal lifespan? $\endgroup$– RonJohnCommented Mar 13, 2019 at 13:47
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7$\begingroup$ Two words: Short Lifespan. Even queen bees don't produce eggs forever - they grow old and die like everything else. If the average lifespan of a species is short enough, they won't run out of eggs. Simple as that. $\endgroup$– Darrel HoffmanCommented Mar 13, 2019 at 13:56
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3$\begingroup$ The "after a certain age" is in the fetal state. Humans are born with all the eggs they will ever have. I don't have the spoons to look it up for all mammals, but it's going to be the same or similar. $\endgroup$– CynCommented Mar 13, 2019 at 14:46
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$\begingroup$ Lots of animals die after first spawn -- salmon, squid, ... . You want something which produces multiple spawns and doesn't "age out" ? $\endgroup$– Carl WitthoftCommented Mar 13, 2019 at 15:21
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1$\begingroup$ Naked mole rats have a "queen". You probably want to read up on them, they're fascinating. $\endgroup$– RemcoGerlichCommented Mar 14, 2019 at 9:56
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6 Answers
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The concept of a menopause is actually unusual, it's known to exist in the wild in 5 species, Humans, Orcas, Belugas, Narwhals, Short Finned Pilot Whales. While some other species exhibit menopause in captivity, others are definitely known not to e.g. cats and dogs.
In all other species the females are believed to remain fertile for their entire lives.
The only queen mammal I'm aware of is the naked mole rat.
The relationships between the queen and the breeding males may last for many years; other females are temporarily sterile. Queens live from 13 to 18 years, and are extremely hostile to other females behaving like queens, or producing hormones for becoming queens. When the queen dies, another female takes her place, sometimes after a violent struggle with her competitors. Once established, the new queen's body expands the space between the vertebrae in her backbone to become longer and ready to bear pups.
answered Mar 13, 2019 at 8:42
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6$\begingroup$ This answer actually surprised me quite a bit. I wasn't aware that menopause was so rare. So, in a sense, for other mammals what blocks older females from procreating isn't fertility, but the actual ability for the body to sustain the pregnancy? $\endgroup$– MermakerCommented Mar 13, 2019 at 12:19
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11$\begingroup$ @T.Sar, there's a theory that basically says something eats them before they become infertile. Note that all known species are at or close to the top of the food chain and highly social, so an individual no longer capable of surviving alone, or increasingly vulnerable due to age isn't necessarily going to be left out to die. Orcas are specifically known for caring for their elderly and disabled pod members. $\endgroup$ Commented Mar 13, 2019 at 12:23
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9$\begingroup$ There's another theory that applies specifically to social species, that says the daughter is likely to have a stronger offspring and that the pod should use the wisdom and knowledge of the matriarch to support grandchildren rather than more children and as such the menopause gives advantage to the group. $\endgroup$ Commented Mar 13, 2019 at 12:30
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5$\begingroup$ @T.Sar, reduction in fertility or successful reproduction as a function of decrepitude is to be expected in all species, this is noted in cats and dogs as well for example, as they get older they're less successful and in heat less often and less reliably, but there's never a full menopause. $\endgroup$ Commented Mar 13, 2019 at 13:37
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2$\begingroup$ Looks like menopause has also been observed in other primates, including chimps and rhesus monkeys (ncbi.nlm.nih.gov/pmc/articles/PMC2553520). This would bolster the social argument. $\endgroup$ Commented Mar 15, 2019 at 0:10
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This article, in National Geographic, says women can produce eggs:
Women may make new eggs throughout their reproductive years—challenging a longstanding tenet that females are born with finite supplies, a new study says. The discovery may also lead to new avenues for improving women's health and fertility.
Who knew?
This means that the "finite number of eggs" reasoning behind menopause is not an absolute one in human biology, let alone non-human.
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3$\begingroup$ Welcome to the site Almight, please take the tour and read up in our help centre about how we work: How to Answer Good find with the article and pretty good first answer. $\endgroup$ Commented Mar 13, 2019 at 14:54
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Women are born with approximately two million eggs in their ovaries, but about eleven thousand of them die every month prior to puberty.
Given one egg per month gives you a ballpark fertility age of 158,000 years (give or take 1,000 years).
If you're changing human biology enough that this is a normal lifespan, you can change it enough to keep the eggs fresh and only release one per month.
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4$\begingroup$ Or maybe even modify the biology to produce eggs to outpace their release? $\endgroup$– corsiKaCommented Mar 13, 2019 at 15:06
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2$\begingroup$ Production of new eggs throughout life seems more likely. Menopause may be an evolutionary response to the degeneration of egg cells after 50ish years in storage. Most mammals do not live this long. Humans are a long-lived social species in which elderly females have a very useful role to play (teaching and child-care), but breeding from degraded eggs would be a strong evolutionary pressure against a long life. The harder bit to engineer would be getting brain cells to reproduce as needed. They also start to degenerate, and the redundant suppy of brain cells only lasts so long. $\endgroup$– nigel222Commented Mar 14, 2019 at 13:16
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$\begingroup$ @nigel222 "Menopause may be an evolutionary response to the degeneration of egg cells after 50ish years in storage" Humans have not been living long enough to such an age, to get an evolutionary response $\endgroup$ Commented Mar 15, 2019 at 13:45
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$\begingroup$ @Christian: They definitely have been. You're thinking no one lived very long because you've seen the life expectancy figures at birth, and infant/childhood mortality was insane before vaccines, antibiotics, reliable food and clean water supplies, etc. Based on modern hunter-gatherers (who lack most or all of these things), life expectancy at age 15 is another 39 years (to age 54), it's just that there is only a 60% chance of reaching 15 in the first place. Neolithic/Bronze Age folks might have had 5 years lower expectancy at 15, but that's still half the population making it to 49. $\endgroup$ Commented Mar 15, 2019 at 15:16
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1$\begingroup$ Point is, it matters more now that we live closer to 80, but there would have been some selective pressures related to aging past 50, even in the Stone Age. Age info from Wikipedia. Of course, the other explanation is that with most of us dying by 50 (and a 50 year old giving birth being unable to care for the child long enough to keep it alive) there wasn't enough pressure to maintain the reproductive system any further than that. $\endgroup$ Commented Mar 15, 2019 at 15:17
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Meerkat are mammals that have "queens" and a hive-like colony. So the phenomena of queen mammals already exists.
Basically the arrangement is that one or two females do all the breeding for a colony. The rest of the colony look after, feed the children, take care of the "queens", and so on. This is pretty much an identical set up to bees, but with fewer workers, and none of the haploid-ness.
There are a lot of intricacies to having a colony that is based around one or two females doing all the breeding that you can look into. For example avoiding inbreeding. However with regard to your specific concern:
Meerkats do not have infinite eggs, and don't need them. Infinite eggs are not required for animals that have finite lifespans. These animals only need to have more eggs than they can use in their lifetime.
answered Mar 13, 2019 at 14:32
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The main issue here is that female mammals don't "produce" eggs, they mature them. every egg a female mammal will ever have is already present in the ovaries at birth.
To have a mammal with indefinite breeding age, and to reduce the negative effects of age on the egg (older eggs have had more time to become damaged), females must indeed produce eggs on the spot, similar to how the male produce sperm; sperm cells are always new and fresh, since they did not have the time to degrade the way eggs do.
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2$\begingroup$ The tools for making sperm don't age perfectly, either... en.wikipedia.org/wiki/Paternal_age_effect $\endgroup$ Commented Mar 13, 2019 at 14:13
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1$\begingroup$ True; but better than pre-existing proto-eggs (the correct name for them escapes me at the time). Such a tool could be improved to age perfectly, but the current human ovary will inevitably run out, sometime, giving a maximum breeding age and amount of offspring for the female, not so much for the male $\endgroup$– ThisIsMeCommented Mar 13, 2019 at 14:15
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The reason why women don't produce eggs for their entire life (making that National Geographic article linked in another answer somewhat dubious) is that this is not in any way in nature's interest. Read "nature" as either "evolution" or "fitness", however you like.
The incidence of several hereditary defects is directly linked to the mother's age, and goes up exponentially (not linearly). The reason for a 45 year old woman having such a high risk is that, well, her eggs and her DNA are 45 years old.
For that same reason, nature doesn't want 50 or 60 year olds to deliver, even if food supply and longeviety allowed for it. There's enough eggs in one woman for a couple of hundred thousand years, so 100 years wouldn't be a technical problem -- but nature doesn't want that. Because what they might deliver would have a high likelihood of being vastly inferior.
Nature isn't loving, kind, and altruistic -- she is a mean bitch. Nature doesn't cater for the inferior. If you aren't good, you are undesired (because you take away precious food and water from the more worthy).
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1$\begingroup$ "Her eggs are 45 years old" - only if they were born with her. If she created them on the spot, they might only be a few months old. The DNA will be 45 years old, but if that is a problem, why is it not a problem for men? $\endgroup$ Commented Mar 14, 2019 at 17:26
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$\begingroup$ @MartinBonner: The woman does not create eggs on the spot, please do not adhere to this nonsense. If she is 45, her eggs, and the DNA within are 45 years old. That's why e.g. Edwards, Down, or Pätau syndrome (and a few others) depend so drastically on the mother's age. The DNA within a 90 year old man's sperm cells is 64 days old (possibly a few more, if abstinent for longer than 2 months). Stem-spermatogonies, prior to Mitosis, are plain normal cells with all normal mechanisms, including DNA repair (and apoptosis which will "fix" trisomies). $\endgroup$– DamonCommented Mar 14, 2019 at 17:40
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$\begingroup$ This is World Building. We are allowed to imagine other possibilities here; continuous production of eggs doesn't seem a particularly unreasonable one. If there is some evidence if happens to a certain extent in real life, that's even better (age related risks of Down's syndrome would still apply if 90% of the released eggs were born with the woman, and only 10% were newly generated.) $\endgroup$ Commented Mar 14, 2019 at 17:43