I'm working on the biology of a fantasy race of very large human-like beings (think something like the Vrykul from WoW or the Norn from Guild Wars), and got stuck on one aspect of their development as infants.

Relative to other species, human babies can be considered somewhat "undercooked" - or, putting in Gordon Ramsay's words - "f***** raw!".

They are relatively weaker and less functional than the offspring of other species, demanding way more attention and effort from their guardians for quite a while.

Even a somewhat basic thing like walking takes several months to develop - sometimes over a year.

My research on the "whys" of this pointed me towards the idea that human babies need to be born earlier than what most other species would consider "done" because of the physiology of the human body. Our heads are simply too big, and waiting out for the proper time to be born with the "basic skill set" in place would make impossible for the mother to give birth safely to their child. Even with our current biology and gestational period, giving birth is no easy task - it is incredibly taxing on the mother and, while some can be up and about as if it was no big deal a few minutes later, it isn't uncommon for a mother to be in need for a good amount of rest and recovery afterwards.

When I bring this to the context of human-like humanoid species with the same overall intelligence and general "build" but way larger in size, a few considerations open up. I mean, when the mothers of this human-like species are over 9-feet tall, one can't help but wonder if the "extra space" wouldn't allow them to give birth to more developed babies, lessening the initial strain of raising a child considerably.

So, to my doubts.

Would a considerably larger human-like species be able to give birth to more developed babies? If so, by how much? Would those babies be able to walk right away after birth, or at least a few days after? Would this reduce the effort needed by the parents on the first year of life of their child? Would any of this need a longer pregnancy?

Note to people answering: While this is a fantasy world and I could handwave anything away as "magic", I would prefer science-based answers for this question.

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    $\begingroup$ A big chunk of WHY we are so successful is because we can defer more than half of the offspring's fetal development to happen outside the womb. This frees the mother to be productive and protective sooner, allows larger braincase development in the child than the birth canal could accommodate, allows infant care to be diversified to other individuals, etc. In effect humans are only "born" some 3 years after conception, it's just that we only spend the first 9 months actually in the womb. $\endgroup$
    – PcMan
    Jan 27, 2021 at 13:29
  • $\begingroup$ @PcMan I'm not sure if we are successful because we can do that, or if we are successful despite needing to do that. You have a good point, tho. Do you have any article I can read about that? $\endgroup$
    – Mermaker
    Jan 27, 2021 at 13:52
  • $\begingroup$ There is a connection to the learning ability. We are where we are because we learn near everything, with very little preprogrammed behaviour. You'd give a larger, later born baby a head start for things like walking, yes, but there is a possibility that it comes with a cost on the learning ability. $\endgroup$
    – Anderas
    Jan 27, 2021 at 14:41
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    $\begingroup$ So you're proposing that certain humanoids are born in a semi developed state similar to how marsupials are born? After being born marsupials remain in a pouch, almost like a second dry womb, where they remain attached to their mother's teat & the quality of the milk various over time as the young marsupial develops in the pouch. How will will your humanoids develop after being born & how will their nutritional & developmental needs be met? $\endgroup$
    – user81881
    Jan 27, 2021 at 14:51
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    $\begingroup$ There's also the theory that our babies being so undeveloped actually helped us on the social plane, as an incentive to stay together as a group to protect the young and the mothers. Species that do not need that might turn out to be less social than humans, and thus less civilized. $\endgroup$ Feb 3, 2021 at 15:56

6 Answers 6


Some time ago I read in a paper (I don't remember where, else I would provide the relevant citation) that, holding constant the constraints you mention, human babies are born at the time where staying in the womb longer would simply starve their mother to death, because their energy need becomes higher than what the mother's metabolism can supply.

Considering that usually the larger an animal the lower the specific metabolic rate is (lower surface to volume ratio, thus less waste of energy), a larger humanoid might be able to bear the baby for a longer time, providing that among the physiological changes of the pregnancy there is also an increase in the specific metabolic rate.

To pair this with the constraints of passing through the mother's hips to be born, it would probably mean that the newborn would be comparatively smaller than a human baby is with respect to the adult, and would need to have a more accelerated growth during infancy to catch up with the adult size. Let's say, just for the sake of an example, that if your humanoid is 3 times the size of a human, their baby wouldn't be 3 times the size of a human baby but only 2 times, while being functionally more mature.

An accelerated growth rate means increased energy demand, so I guess the parents would struggle less during delivery but more after it to keep up with the hungry baby.

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    $\begingroup$ Is this the article you are referring to? $\endgroup$
    – Mermaker
    Jan 27, 2021 at 14:01
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    $\begingroup$ Thanks for pointing out this theory. I'm giving a read to it, and it is a very interesting take on this subject! $\endgroup$
    – Mermaker
    Jan 27, 2021 at 14:18
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    $\begingroup$ Elephants have pregnancies of 18-22 months. (source:britannica.com/animal/elephant-mammal/… ) $\endgroup$
    – Karst
    Jan 27, 2021 at 22:05
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    $\begingroup$ I wonder how the article accounts for successful gestation of twins and multiple births $\endgroup$
    – user2510
    Feb 3, 2021 at 9:21
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    $\begingroup$ @dima aren't twins more often than not are born earlier than single births? $\endgroup$
    – Mermaker
    Feb 5, 2021 at 0:09

There are many reasons why humans are born the way they are.

Consider that largest baby relative to parent body size is kiwi egg (1/2). The tsetse fly produces a single large larva (third instar). Even among mammals, there are giraffes (1/10).

On the time scale, elephants, whales, rhinos, giraffes, donkeys, zebras, camels, sea lions and alpacas have gestation longer than a year. These are all large animals, though not all exceedingly so.

Still, I think that larger humanoids would have longer gestation than smaller humanoids.

There's the other side of human development — our babies are born with huge heads and small bodies, and we've improved this ratio as we developed as primates. Also our brains grow notably longer after birth (ref). I believe the reason is that animals that live in communities, especially developed communities can take care for their offspring much longer, which allows delivering "underdeveloped" young.

I suspect that all things being equal, larger humanoids could have larger head-to-body ratio at birth, but ultimately, it's the culture / social organisation / safety from predators that has the most effect. You could use the family circumstances to tweak your larger humanoid babies this way or that.


One of the significant reasons as to why human babies take so long to learn how to walk (compared to other species) is that our brains are not formed the same.

In humans, the prefrontal cortex (at the front) is much larger than other species (which is why we have large foreheads). In most other animals, the cerebellum (back of the head) is larger, which contains most "innate" knowledge that animals use from birth. Add in the fact that walking for humans is a lot more complex than for other animals (biped vs quadruped, it's tougher to find balance), and you have the perfect cocktail for human babies being so useless at birth.

The fact that we have such a developed prefrontal coretex is one of the things that makes us humans - we have insane patern recognition and skill learning that other mammals lack. We can find these in other primates like chimpanzees too but to a lesser degree.

Ray Kurzweil talks about this a bit in this TED talk, I can't remember other sources as it comes from some conferences and such, I work in biology research.

EDIT: Just realised that I never explicitly answered the question. To clarify, I think it would be impossible for a species as "intellignet" as humans to be fully functional at birth due to this. Shortening this learning period (multiple years in humans) would lead to a very different society and probably one that would never reach higher education and therefore be quite technologically stunted. If this is ok with the species you are thinking of, then roll with it, otherwise you might need to handwave it away or make up another explanation, which would add to complexity.


When it comes to biology, there are very few things that isn't possible.

First, i'm not a biologist, this is an opinion based on my limited knowledge on evolution, biology etc.

To say that babies are born "early" because the head otherwise couldn't pass through the birth canal, is a bit of a mis-representation of the truth. There is no reason the female can't simple have a larger birth canal. This would of course require a change to the pelvis, that would affect the females ability to walk (probably in a negative way, as it hasn't happend) This is super bad, for a hunter/gatherer society based around walking a lot to gather/hunt food.

So the reason why humans are the way they are, is essentially a "path of least resistance" scenario. A longer pregnancy would give the baby a greater change at surviving, but negatively impact the mothers ability to survive. At some point it is simply more cost-effective to have one more baby die early, and leave the mother alive to birth two more babies later. (morally this is of course horrible, but evolution doesn't really care sadly)

As for your question: A humanoid that's, say 50% larger, would most likely have different ways of acquiring food. There would be a large increase in energy consumption, but the increased size would be unlikely to enhance the humanoids ability to hunt as humans do by exhausting it's prey (probably). Though they would be much more likely to be able to simply beat it's prey (think angry gorilla, they are scary!)

TLDR: I don't find it unreasonable to assume a larger humanoid would be able to have a considerably longer gestation period, due to the probable changes in the way they get food, lessening the consequences for birthing a more developed child.


They have a huge immobile Queen

Just like with termites, the queen humanoid is comparatively huge. She is attended constantly by humanoid workers whose sole purpose in life is to provide her with nutrition and clear away waste. When a fully formed humanoid is born, they are taken away to humanoid 'school' to learn language skills and the ways of their caste; worker, hunter/gatherer, warrior, etc.

Population control is achieved by varying the number of queens in any particular town or village.

More recently, with the advent of technology, the preborn humans can learn language skills from inside the womb by having recordings blasted at them through the queen's stomach.



Well no because bigger creatures give birth to bigger babies.

Example: A monkey is bigger than a rat but a monkey's baby is bigger than a rat baby.


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