Egg Laying Humanoids... What Would Physics Allow For?

[Spacescifi]

 Scenario: So we have your standard palette swapped humanoid scifi race (which looks all but human in name only like in Star Trek) but they lay eggs instead of live birth like humans.

Once the baby leaves the egg it will still be dependant on the mother for breast feeding etc until it grows strong enough.

Main Questions:

1. Would or should pregnancy take longer or the same (9 months give or take)?

2. How long would gestation take? How long should it take ideally for a healthy baby as the egg incubates?

3. For the sake of argument the shell is thin and leathery to the touch, meaning it won't crack so much as tear. Which is exactly how babies exit out of them, by tearing their way out when ready.

Your thoughts?

 

[magnemoe]

I say pregnancy would be much shorter as the baby would develop in the egg. 
Downside is that the egg size is limited by the hole in the hip bone. 
This is already an major problem for human babies and mothers and the baby has to fit inside the egg.  If the egg was not hard it would be easier but it would be an pretty large egg anyway. 
Redesigning the hip would be pretty required i think

[Spacescifi]

1 hour ago, magnemoe said:

I say pregnancy would be much shorter as the baby would develop in the egg. 
Downside is that the egg size is limited by the hole in the hip bone. 
This is already an major problem for human babies and mothers and the baby has to fit inside the egg.  If the egg was not hard it would be easier but it would be an pretty large egg anyway. 
Redesigning the hip would be pretty required i think

 

According to google AI: 

The average head circumference of a newborn is around 13 3/4 inches (35 cm), while the average length at birth is 19 to 20 inches (about 50 cm), with a normal range of 18 to 22 inches (45.7 to 60 cm).
Here's a more detailed breakdown:

    Head Circumference:
    The average newborn's head measures around 13 3/4 inches (35 cm).

Length:
The average length at birth for a full-term baby is 19 to 20 inches (about 50 cm), with a normal range of 18 to 22 inches (45.7 to 60 cm).
Head Growth:
The bones in a baby's skull are still growing together, and the skull is growing faster during the first four months than at any other time in her life.
Fetal Macrosomia:
The term "fetal macrosomia" is used to describe a newborn who's much larger than average, weighing more than 8 pounds, 13 ounces (4,000 grams).
Birth Weight:
Full-term babies typically weigh between 5 pounds 11 1/2 ounces and 8 pounds, 5 3/4 ounces at birth.

 

My analysis: If the leather egg is thin then you may not need wider hips. It would have to be stronger against tearing on the outside than inside obviously.

Otherwise perhaps the alien women would need wider hips than normal human women, is that what you are saying?

I suppose another way to do it without wider hips would be if the alien bones were more flexible than human ones. Being able to bend  or expand more without breaking before returning to normal shape.

Edited March 15 by Spacescifi

[Nuke]

ever seen alien nation?

[darthgently]

3 hours ago, Spacescifi said:

 Scenario: So we have your standard palette swapped humanoid scifi race (which looks all but human in name only like in Star Trek) but they lay eggs instead of live birth like humans.

Once the baby leaves the egg it will still be dependant on the mother for breast feeding etc until it grows strong enough.

Main Questions:

1. Would or should pregnancy take longer or the same (9 months give or take)?

2. How long would gestation take? How long should it take ideally for a healthy baby as the egg incubates?

3. For the sake of argument the shell is thin and leathery to the touch, meaning it won't crack so much as tear. Which is exactly how babies exit out of them, by tearing their way out when ready.

Your thoughts?

 

It has recently been found that mothers have their children’s dna permanently as part of their bodies after giving birth that stays a part of them for the rest of their lives.  Not merely the maternal portion, but the actual full dna of the children.  
One might  wonder if this would be the case in an egg laying variant of us.  What would it entail for the mother-child bond?  Or the bond between the mother and the entire family as she may not have her children’s paternal dna as part of her body any longer

On further thought, the lack of a placental connection could have big effects on the mother-child physiological, and perhaps psychological, relationship

[Spacescifi]

29 minutes ago, Nuke said:

ever seen alien nation?

No.

[Exploro]

The title of this thread is irksome. The question is not whether physics would allow for a humanoid animal to birth offspring within an egg. Rather the question is whether doing so garners any evolutionary advantage to such a hypothetical creature.

Edited March 19 by Exploro

[Spacescifi]

32 minutes ago, Exploro said:

The title of this thread is irksome. The question is not whether physics would allow for a humanoid animal to birth offspring within an egg. Rather the question is whether doing so garners any evolutionary advantage to such a hypothetical creature.

Has already been answered. Mothers have faster pregnancies and can spend less time being pregnant. Would work well in a matriarchal society where females grossly outnumbered males because for some reason male births are in the minority (much the same as ants because of short life spans and only serving the role of reproduction).

[tomf]

Non equal gender ratios can't evolve in species that do genetics the same way as humans, i.e. half the genes in an individual come from a father and half from a mother. 

Imagine that there is a gender imbalance e.g. with more females, it would be a huge genetic advantage for a gene to cause it's carrier to have more male children as each male fathers more progeny then each female on average. 

The "more males" gene would spread through the population until there are no longer more females than males. 

Social insects do their genetics fundamentally differently allowing for different results.

[Spacescifi]

1 hour ago, tomf said:

Non equal gender ratios can't evolve in species that do genetics the same way as humans, i.e. half the genes in an individual come from a father and half from a mother. 

Imagine that there is a gender imbalance e.g. with more females, it would be a huge genetic advantage for a gene to cause it's carrier to have more male children as each male fathers more progeny then each female on average. 

The "more males" gene would spread through the population until there are no longer more females than males. 

Social insects do their genetics fundamentally differently allowing for different results.

Ants and bees have a higher female population because males have short lifespans. With male bees the act of mating is fatal, and male ants have a one way trip to mate and or die because not only is their lifespan short but during winter the colony will kick out excess males to die in the cold to preserve the more valuable workers.

If male ants and male bees lived longer it would balance out the male/female ratio but because they don't it is what it is.

[magnemoe]

On 3/19/2025 at 2:42 PM, Spacescifi said:

Ants and bees have a higher female population because males have short lifespans. With male bees the act of mating is fatal, and male ants have a one way trip to mate and or die because not only is their lifespan short but during winter the colony will kick out excess males to die in the cold to preserve the more valuable workers.

If male ants and male bees lived longer it would balance out the male/female ratio but because they don't it is what it is.

Social insects also have weird genetic, all the workers are children of the queen I think is more important than lifespan.  Now if they kill off the males where do they get new ones? 
If the queen birthed them you are just inbreeding?

Else I agree with you, having an majority male population is even more stupid. Majority female makes sense if designed it for rapid growth.  Majority male, don't see any benefit. But majority male is popular in fiction for some reason?
Then you have the naked mole rats who is mammals but behaves like social insects. Hard to see how to get intelligence out of it compared to an pack of smart social animals. 
But if you want the social insect society here you have it. 
Note that the queen does not control the pack, even less so than an leader of an stone age human tribe because we can discuss and plan. 
Will it be less rigid if intelligent or will it not work?

[Spacescifi]

3 hours ago, magnemoe said:

Social insects also have weird genetic, all the workers are children of the queen I think is more important than lifespan.  Now if they kill off the males where do they get new ones? 
If the queen birthed them you are just inbreeding?

Else I agree with you, having an majority male population is even more stupid. Majority female makes sense if designed it for rapid growth.  Majority male, don't see any benefit. But majority male is popular in fiction for some reason?
Then you have the naked mole rats who is mammals but behaves like social insects. Hard to see how to get intelligence out of it compared to an pack of smart social animals. 
But if you want the social insect society here you have it. 
Note that the queen does not control the pack, even less so than an leader of an stone age human tribe because we can discuss and plan. 
Will it be less rigid if intelligent or will it not work?

 

Insect males, particularly ants actually come from eggs that can be stored for long periods inside queen

Their genes, that of the males, is diffefent from females because I read that they totally lack the female gene.

I am not sure if I am recalling it correctly, but I remember reading that ant males come from unfertilzed eggs, and females come from fertilized eggs.

Which would mean females posess both male and female genes but males do not.

[RCgothic]

Hip size need not be a limit. It is in humans, but we're taking about aliens where the birth canal needs not pass through the pelvis, or the pelvis could have evolved more sensibly.

For a hard shell, passage through a human-like birth canal would restrict the max size of brain at hatching compared to at birth. Baby heads squish, hard shells do not. Even if the brain is not developed at the time of laying, it'd develop under the constraints of a shell that needs to pass the birth canal.

Soft shell eggs could potentially change shape/relax shape after laying though to accommodate a larger brain than could be passed through a birth canal. The brain wouldn't have developed at that point, and a shell would potentially be able to accommodate a greater degree of squish. Births might even be comparable easy, laying a long thin egg that adopts a more spherical profile once passed.

However, everything the baby needs for development would need to be in the egg, whereas in utero they can be continuously supplied with what they need by the mother. So an egg may need to be comparatively large to fuel that growth compared to a baby. From what I can look up, chicken eggs convert egg mass into baby mass at an efficiency of somewhere between 60-80%. So an equivalently heavy egg could be expected to produce a comparatively small baby. 

However, a lot of the mass loss is through evaporation, so potentially eggs laid in water might better retain water mass in the baby.

 

So there are potentially a few interesting differences there.

 

In terms of gender ratios at birth, egg-laying species can exhibit much greater disparities than mammals*.

The effects of temperature on egg-laying species can be hugely influential, with clutches ranging from 100% male to 100% female depending. The body condition of the mother can also have a strong influence - between 25% to 87% daughters in peafowl.

(*Pygmy hippos in captivity are mammals with a distorted female:male birth ratio of up to approx 3:2. Apparently the male can control the ratio of X:Y in their gametes to a degree.)

Edited Tuesday at 11:52 AM by RCgothic