Would a species with 3 sexes be more adept at warfare and hard labor compared to humans?

Question

For my fantasy story, I was trying to conceive of a three-gendered species for more uniqueness. I finally thought up an idea that might make biological sense. For mammals, the male sex has the sperm cells while the female sex has the egg cells and gives live birth to children. For fishes, amphibians, reptiles, and birds; the male sex has the sperm cells while the female sex has the egg cells and lays eggs.

My idea is that for a humanoid species called Nesians, they have three sexes: a male sex, a female sex, and a surrogate sex. The male sex has the sperm cells, the female sex has the egg cells, the surrogate sex doesn't have sex cells, but they have a uterus. How reproduction works is that the male sex and female sex exchanges genes and create a zygote, and then later on the male sex copulates with the surrogate sex, depositing the zygote at the end. If the male doesn't deposit the zygote within two weeks, the zygote dies. The surrogate sex is also the one who breastfeeds.

So effectively, Nesians offload the task of carrying and birthing children onto a completely different sex within their species. The advantage of this system is that since female Nesians don't have to worry about pregnancy or menstruation or other female health concerns, they can be just as large/strong as male Nesians and work all the time. This means that 2/3 of the population can be devoted to physical labor or being a soldier instead of only 1/2; that is a 1/6 increase. The disadvantage is that sexual reproduction now requires three individuals instead of 2.

Nesians effectively have the benefits of artificial wombs or xenopregnancies at a much earlier stage in history. Only 1/3rd of the population will also suffer from a physical disparity instead of 1/2 of it.

Assuming evolution created a species this way, would they have a major advantage over humans when it comes to pre-industrial society due to a greater strong labor pool? Or is there some unintended consequences that I'm missing that will ruin everything?

Answer 1

They still need a similar ratio of the population devoted to child bearing.

The main factor determining success at warfare and labour is how many bodies you have. This species will naturally need to produce babies at a faster rate to match sexually dimorphic species.

So, a sexually dimorphic species can have say 50% of women be pregnant at any one time, with 50% devoted to useful labour and warfare. By contrast, this species will need to have around 75% of the incubator population devoted to child bearing to match the birth rate of humans because of their lower ratio.

Calorie intake is more important than sheer numbers.

Soldiers and labourers are extremely expensive to make. A normal woman requires 1500 calories to maintain per day, while a normal man requires 2000 calories. Woman, as a lower performance but lower expense human resource, are more efficient for jobs which don't require brute physical strength, for example picking berries or hunting small prey.

Human men, as a higher performance but lower efficiency model, require more resources but can do heavier lifting tasks. That said, to train for war or for heavy lifting in construction their calorie needs might swell to 4000-8000 a day. As such, their ability to do these tasks is very reliant on how efficient their society is at collecting food. Since women are often more efficient at collecting food it makes sense to have more of those human resource models.

In addition, animals are often even more efficient at many muscular tasks, since some like horses or oxen can convert useless grass into useful energy.

Nesians will be worse in the short term, better in the medium turn, and worse in the long run.

Most militaries and labouring projects worked by having everyone be trained for them and then having a small fraction be prepared for war, so your trimorphic species is probably going to be able to sustain slightly smaller numbers of soldiers since it's less geared for food collection but be able to replace them more easily since it has a higher degree of people with high performance low efficiency models.

Human militaries will be able to throw more bodies at the problem since they have more of the calorie efficient female models supplying them. In the medium turn the Nesians will have the advantage as a higher ratio of their population is well suited for warfare. In the long run, due to their complicated reproduction and wear and tear on the surrogate sex and limited food, they'll be at a disadvantage.

Answer 2

Your current arrangement certainly has a unique twist, so good work thinking outside of the box to create something different!

Reading your question, I'd say that your organisation of the sexes feels as a bit too convenient as a fighting-and-labour culture for such a complex creature. Humans and humanoids are complex animals and, while we're good at cooperating, we don't really form, nor would we function well in, hives. Your current 3-sex arrangement feels quite invertebrates-in-a-hivey, to me. I think the main issue here is with how much coordination is required for the three sexes to produce the next generation. Invertebrates don't care who they do the do with, but your creatures are humanoids, which implies they probably have rules and nuances and probably put emotional investment into their sex/love lives, so would they be able to reproduce often enough, even if thruples are the norm, even if they tend to only meet to mate and then part company?

I say "often enough" because your species also has a strong lean towards fighting and labour. Both of these activities require for lots of new candidates to be born. Fighters tend to die in battle, and labourers get worn out and need replacing. So the 3-sex reproduction cycle needs to be very effective in producing lots of both types.

Also, you mentioned bees. Could bees make for a better model, here? While there are sperm-producers and ovum-producers among bees, they can be argued to have three 'sexes': queen, worker, and drone. Notably, when a queen produces an unfertilised egg, it will hatch into a drone. No worker (the hive's males) required.

However, it sounds like your humanoids gestate, rather than laying eggs, and I think that's the rub for you. I assume you'd rather they carry on gestating rather than make them into egg-layers, which means that at least some of your population will be regularly out of action for fighting or labouring - unless you make some tweaks to how vulnerable they are while gestating. Kangaroos have a good system for this that you might want to draw on. I wonder if you could write your species to streamline both gestation and nurturing of the next generation, thereby freeing up everyone to keep fighting or working?

I hope that helps!

Answer 3

It can make a difference and it is not necessary

Humans are a poor example for fitness. Compared to some creatures in the animal kingdom we are remarkably similar already. In our current society the differences are exaggerated thanks to culture, but tgere is plenty of evidence that women have donned physical or warrior roles throughout time. The standard deviation is much bigger than the average differences of men and women. Only at the top levels we see the differences widen, but extremes are a bad metric for these things.

Animal differences

In animals the roles are easily reversed. Hyenas and prides of lions are mostly ruled by the females. This is again benign. If we look at Black Widow spiders, or mantises, then we can see the fenales are many times bigger and stronger than the male counterparts. It shows a big difference in ideology of the animal kingdom. Males are inconsequential and only need to survive long enough for breeding. Afterwards they might be eaten, while the female offers the strength and protection for the brood.

Gender differences can be extremely exaggerated, dependent on how the survival strategies are. No survival strategy is exclusive, so different strategies emerge everywhere.

Humans could have evolved differently, where females would be large and strong, able to carry and defend the offspring, while the men could be scrawny things that use their intelligence. Together they form power couples in a tightly knit society. Or reverse the roles. It changes the strategies and survival tactics, but they can survive.

This all to say that gender differences can make a hige impact on physical ability and war.

Dogs

Let us look at the descendants of the venerable wolf. We have great danes and chihuahuas. Physically very different, but still of the same species. They can breed. I'm not saying it is wise to do so, bit it illustrates that within a species you can have radical physical differences. Regardless whether they are male or female, they can be big or small, short haired or long haired, big nose small nose, good smell receptors and bad. With selective breeding you can do the same for humans. Just as a quick example, the Habsburg chins. But you can get very creative if you select certain attributes long enough. This illustrates that extra genders are unnecessary.

New complications

The complications from three genders can be higher than two. You've moved a few problems like periods to a third gender, but you've extended the chain of reproduction. From increasing social complexity to more things to go wrong in each stage, you're introducing more problems we haven't even thought of yet. Having a third one could just as easily be a bad idea.

Conclusion

Extra genders can have some opportunities, but the question is why. You've got so much diversity to play with already, that extra genders is not necessary. That being said, it can be a good excuse. Do not let the possible impractical nature of three genders block you. If you say it is in a book, it often is accepted for the story.

Answer 4

My idea is that for a humanoid species called Nesians, they have three sexes: a male sex, a female sex, and a surrogate sex.

Impossible to tell

I assume you just took humans and modified them to have 3 sexes? This will require radical modification of human biology, with the most unpredictable consequences. We can't even be sure if those creatures would be able to survive on their own at all, let alone to be superior to humans.

They must be products of an intelligent design

I don't think that such creatures can arise from natural selection, as such reproduction can be beneficial only when the creatures are social. And sexual reproduction is more ancient than social animals. Presented way of reproduction is too radical departure from established in ancient pre-social times way of reproduction.