I will be making several posts on this community regarding questions which involve the design specifications of an alternate human species I designed. Because I'm not a biologist, and I have no idea what I'm doing half of the time. But I strive for realism and immersion, and I prefer to seek out the aid of people who know what they are doing.

This question pertains to the plausibility of hollow breasts in a nearly human species.

This is the basic concept and I'm just asking for an analysis and critique of the concept.

So the basic concept of these alternate humans breasts is that they function kinda like self-replenishing water balloons. The Breast Milk would be produced by the mammary glands which would be moved to the very back of the breasts, against the chest wall. The actual interior of the breast would comprise of a bladder-like organ that stores the breast milk which can, in turn, be released from the breast with a squeeze. I would presume that a sponge-like organ should be put in the front area of the breast which would ''filter'' the breast milk and help it exit the breast in an "organized" fashion.

I'd assume that the breast structure around the bladder-like organ would comprise of fat, tissue, and skin that ranges at 5 to 11mm in thickness depending on what is a better width. I think the breasts should be able to hold at least 44 ounces worth of fluid.

These alternate humans automatically start producing milk as their breasts develop in their mid-teens but it can start earlier if they become pregnant at an earlier age. They will continue to produce breast milk automatically until their mid-'40s. After this period, the breasts will shrink with age to the point of becoming flat. I'd assume that this could be rendered possible by hyper-flexible and malleable skin.

Due to the unique design of these breasts, I'd assume that they would be prone to natural gainaxing since they are pretty much like fleshy water balloons.

Now there are several problems that seem to be poised by this design. It would seem that the breasts would keep producing milk 24/7 from the time they develop to the time that they become obsolete. This would mean that females would have to milk themselves consistently every few hours, as neglect could result in an increasingly unbearable weight gain in the breasts, which are already heavy due to their unique structure. The breastmilk could probably spoil inside the breasts and give them an infection.

One desired concept would be that the breasts stop producing milk once they become full at 44 ounces and if they start losing volume from being milked they will automatically produce more milk as milk is lost, effectively creating a perpetual flow. I'm not sure if this is possible as it would require a "biological computer".

I'm also aware that this perpetual milk production is not really possible as it would require an unsustainable intake of nutrients. I've experimented with the idea of these alternate humans being capable of unwillingly absorbing moisture around them, to use for both milk and semen production or recycling more of their ingested liquids for bodily purposes than humans do. I also don't know how this could work either.

Also, I think the breasts would be prone to natural gainaxing due to their structure as fleshy water balloons. Also, would the females be able to hear the milk sloshing around in their breasts due to the hollow structure?

Any suggestions for how I could rectify these problems?

Thank you in Advance btw.

  • 2
    $\begingroup$ What keeps ordinary women from the problems you're citing, given that they all basically boil down to overproduction of milk? I'm not an expert here, but I'd advise looking into that first. $\endgroup$
    – Palarran
    Feb 20, 2020 at 1:16
  • 1
    $\begingroup$ What amount of secretion (daily) are you looking for? I think this (rather than hollow breasts) would be the main hurdle. $\endgroup$
    – Alexander
    Feb 20, 2020 at 1:16
  • 2
    $\begingroup$ "After this period, the breasts will shrink with age to the point of becoming flat" - unfortunately this is not how human skin works, so this is another challenge. $\endgroup$
    – Alexander
    Feb 20, 2020 at 1:18
  • 2
    $\begingroup$ You state your problems as essentially being that your species will endlessly produce milk (for a few decades, at least), far too much milk, and will need to find ways to use or dispose of that excess milk. Why do humans not have such problems with their breasts? Look into whatever mechanism controls milk production in humans; it should give you somewhere to start in defeating that problem in your species. Incidentally, I'd suggest reducing the rate of milk production in general; that would seem to me like something to at least moderate the problem. $\endgroup$
    – Palarran
    Feb 20, 2020 at 2:11
  • 2
    $\begingroup$ When humans produce too much milk and nothing is otherwise removing it... they can leak. I seem to recall that cows can experience pain if not milked. Terran mammals usually don't have a problem with overproduction because they stop producing if nothing is 'taking' their milk; also, they don't start producing until a certain point in pregnancy, and I believe stop a certain time after birth. Unfortunately, the OP has essentially ruled out these mechanisms. (Which, BTW, doesn't seem realistic; there would need to be a reason for such continuous production to be plausible.) $\endgroup$
    – Matthew
    Feb 20, 2020 at 3:16

2 Answers 2


I would use the camel as template.

The guy stores fat on its emblematic upper back "breast" and when the body needs water, it breaks down the fat to produce water.

Say you approach these species as adapted to produce a reserve, increasing the fat/oil reservoir size.The act of lactating could be done away from away from food on weeks long trips.

In our species we didn't evolve to cope with deserts. We got technology. Say the migratory pattern for these humans consisted on munching food, stocking food in all females and then migrating across desert.

Many mammal species are social regarding the nursing, even some cow breeds do it. Picture young unfertile stocking resources to share the nursing and relieve the recovery of those who DID bear progeny.

Old efephant females lead the migratory herd remembering the watering spots. Mix a bit of camel biology, female elephant migratory behavious and deserts.

They armonise in regards as environmental pressure, biological adaptation and finally, the culture that develops.

She of the dried breasts traveled this very same path knows where the water is which caves to avoid which caves are safe. Respect the Dry One, Young Wetter.

  • 1
    $\begingroup$ That's a very interesting concept but I don't really think it properly applies to these alternate humans since they are not just storing the breastmilk but also producing it in a natural over abundance. $\endgroup$ Feb 20, 2020 at 2:04
  • 1
    $\begingroup$ Why? Remember that kalories are harsh mistresses. Why would perpetual expenditure be so vital that it gives enough evolutionary pressuro to justify it. $\endgroup$
    – Gustavo
    Feb 20, 2020 at 2:48

Prolactin is the hormone that controls the production of breast milk. Any physical or chemical mechanism might evolve to regulate the flow by triggering or inhibiting the release of prolactin. Like most bodily systems the production of milk is very well regulated by the body in its natural environment. Issues arise when artificial selection prioritizes milk production above all else as is the case with some dairy cows.

If the need is for a lot of milk then a lot of milk could be generated, if not then it wouldn't be at least in nature. If the bodies have been artificially engineered then almost anything is possible.

If there is a need for a large milk supply to be immediately available “just in case” then I would expect the body to evolve a system to reabsorb the milk to maintain the required balance in the body. The body could also evolve preservatives and specialist immune cells for added protection from microbial attacks if needed.

  • $\begingroup$ The later suggestions sound interesting but are there any real creatures with such an ability? My desired design for these hollow breasts would be that they self replenish for every max ounce that is lost, so if they automatically produce more milk as they are being milked. I'm not sure if that's possible either. $\endgroup$ Feb 20, 2020 at 14:13
  • $\begingroup$ Yes humans will reabsorb milk if it is not used and I suspect all mammals are similar livestrong.com/article/… $\endgroup$
    – Slarty
    Feb 20, 2020 at 15:02
  • $\begingroup$ huh... That's neat I guess. $\endgroup$ Feb 20, 2020 at 18:11

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .