Worldbuilding 201: Alien Sexes
Salutations and greetings! Your favourite alien Limax, VIVIAN! Is back once more with another crazy one on biology! With that we have an obligatory disclaimer as context often eludes people.
Disclaimer: This blogpost is primarily focused on the biology of things and is intentionally made to be narrow to focus on only what results in reproduction. I am not making any judgement calls in social or moral ways when I use positive terms to describe that relates to reproduction or negative terms to the lack of reproduction. Positive and negative in this context refers to how it facilitates or inhibits reproduction, not moral judgements. Life is more than reproduction whether one desires children or not, and, regardless of ability or willingness to reproduce, a person’s value as a person does not diminish.
Now moving on with our lives! You’re all beautiful and important in your own weird crazy wicked ways. One thing to pay attention to is that I am doing basic animal related ones. Plant reproduction is… even more complicated. I will get there… someday.
What is sexual reproduction?
As we all know, sex is quite popular especially on your old underdeveloped interne-
Divinum damn it! Well yeah we can all see how popular sex is but… why is it a thing? Sure it is fun, nice, and all. But what does it do? Well babies of course! ...but you have parthenogenesis (species where unfertilised females can give birth thus not needing males–there is a species now entirely lacking males) and you have bacteria that split into new copies just like our cells, which is asexual reproduction and one I will not go into here. So what does it really add given how difficult it is?
What do you mean what is difficult with sex, Bob? By Divinum, how dumb are you? Of course you ain’t even tried dating. You first gotta find another individual, and if there are different sexes, one of the RIGHT sex. Then you gotta convince them to have sex with you. This can take a lot of energy, and then once you have done all these dances and rituals just to get to the point of doing the deed… if the sexes cannot share the burden, the sexes will have a disproportionate amount of energy invested into the child by just making the offspring! Yes, not raising it, making it!
So what is the gain after all these hardships in the dating pool? Variety. That is right, variety. What kind? Genetic. Sex has the benefit of making it possible that beneficial and good mutations can encounter other similarly good ones in other aspects to make a new super individual that is even better than any of the parents were, without having to mutate! But most importantly, it creates variety in the one thing that multicellular organisms struggle with: their immune system. What do I mean? Okay, you humans have a generation on average at around every 20 years. Bacteria have around 20 minutes when they really go at it, asexually. So how many generations do bacteria get into your generation length? 525 949, yes I calculated it, that is half a million generations. All mutations and differences from their ancestors. That means if multicellular organisms of your size did it asexually (and therefore shared the same genes), there is a high chance that a bacteria will strike gold and find the key to completely destroy you humans because you are virtually genetically identical. This is called the “Red Queen” hypothesis, yes it is from Alice in Wonderland and the Red Queen running but never moving.
So in short, sex is a variety-inducing mechanism to speed up evolution and protect multicellular lifeforms from being genetically similar to the point where microorganisms pose a huge threat.
Number of sexes
So now we have something of what sexual reproduction is and why the bloody thing exists. But can there be only two sexes? OF COURSE NOT! This is speculative fiction, and nature gets real kinky sometimes!
Zero
This is the asexual one. There is no sex to speak of because there is no sexual reproduction, and thus there is no sex in the species. It is extremely rare for this to exist in multicellular lifeforms due to the disadvantages that I spoke about before: lack of variety within the species. However, there are lizards that do parthenogenesis and thus can be said to have zero sexes. We still call them females, however, because the current body is very much female for lizards. There either needs to be something that improves the survivability of the species for this to outweigh that huge negative or generally a sufficiently sophisticated immune system that takes up the problem of lack of variety. I will do a post on immune systems later.
One
This is not being a hermaphrodite. This means that there is one sex, and an important aspect to this is that there is no single individual in reproduction, mating, coupling, whatever, that pays a much greater amount of energy, resources, and time than the other. That is a significant thing in two sexes. One sex (females) pay much more energy in reproduction, and the other sex (males) pay considerably less. For sapient or multicellular, one sex is very rare, and I struggle to come up with a system that could work. A thing I see as an issue is that if either one can take on the more energy intensive role, the species will start developing toward two sexes for specialisation and efficiency, so if you do it, you cannot have such a sexual reproduction system. A rough idea I can come with is that it is likely best to do external reproduction in water, similar to how fish do. If you have any system, please comment below and I will happily read it!
Two
The standard one on earth, and the most common one. This is for a simple reason. You get all the fun! Nah joking. It is the minimum number of sexes required for the variety-inducing property to go into overdrive while also specialising both sexes to make them as efficient as possible in what role they take. As I said in the one sex, when you have two sexes, one takes on the role of investing more energy, and the other invests less. This leads to specific dynamics between the sexes with the classical example being that females are generally more picky about who they reproduce with while males are generally less picky. A minor issue here is that if you encounter a random individual (generally, assuming even distribution between the sexes), there is only a 50% chance mating is possible.
Both
The one my kind is! We Limaces are both 😀 Hermaphroditism is this one generally. What this means is that each individual has both sets of reproductive organs and can take on either the more expensive role or the less expensive one. This has the benefit that when you meet another individual of your own species, there is a 100% chance you both can mate and have babies! But believe it or not, this actually decreases variety compared to having two separate sexes. Why? Because with different sexes, you need more genes and expressions to make up the two different bodies. Another factor with two sexes is that it forces the individuals to look for the opposite sex. Here, hermaphrodites can have anyone and keep going at it. I know 😏 It is believed that in the evolution of two sexes, it was first zero, one, both, then finally two sexes. This tactic of sexual reproduction with hermaphroditism is popular with snails and slugs, but in other clades of animals, it is not popular. Fun fact: certain slugs, I think sea slugs, have penis duels. They fight with their penises to see “who gets to be the baby mumma”; the loser is the mumma. Better luck next time sluggie 🤣 We Limaces do not do this.
More in chain
More sexes! MORE SEX! ...okay no orgies, or maybe? Anyway, when it comes to external reproduction, it can get quite… mixed when it comes to more sexes. But a thing to notice here is this: the more sexes that are required in a single instance of reproduction beyond 2 add absolutely no additional benefit in terms of creating variety and evolutionary speed. It increases costs significantly, however, and thus is generally discouraged. But this is speculative, so fuck evolution! Sometimes quirks happen. Not like I got a trisexed species or something as some big powerful people or anything (Raixher).
By “in chain” I mean that all sexes are involved in reproduction, and none can be left out. I call it “in chain” because when it comes to land animals, the vast majority do internal insemination and development, whether eggs or actual live young. So a postduosexed (I made that prefix, post - after, duo - two) species will likely form chains of reproduction as I have imagined it. While I have imagined it, I might be very narrow in my perceptions and wrong here. If you have more wild ideas, please comment below!
More by dual
This one actually exists in nature: slime moulds. What do I mean with this? What I mean is that you have a number of sexes, let’s assume 9 because Anne loves that number. I might have influenced it. Anyway, you might from my previous section think
Sweet holy mother of dancing Jehova, how are that many gonna chain up? This is going to be an unspeakable orgy of some kind!
Nope, in this case it just means there are 9 sexes that are different, but they are not all equal in any way, sense, or anything. The “by dual” part is that in any reproductive act, only two of the sexes are involved, and the rest are irrelevant. Depending on how sexes are determined, what the conditions for successive reproduction, and all, which sexes can mate with which can be INCREDIBLY complicated. But they still only need 2 individuals in the reproductive act. There is a slime mould that, if I recall correctly, has 3 genes to determine sex. Which, given they are slime moulds, doesn’t give a lot of sexual multimorphism, but hey, we can get real kinky here! Anyway, there are 13 kinds of the first gene, another 13 of the second gene, and 3 of the last one. So a grand total of 507 sexes. THAT IS A LOT! It is more than…. 🖐️ this many. But the thing is, they only need ONE other sex to reproduce. So which sexes work? The ones that have NO genes in common with oneself. So let’s say for the first two genes we use letters and the last one numbers. AA1, AA2, AA3, AB1, etc, all the way up to MM3. If an AB1 meets a GH1, that won’t work because they share the last gene in common. Same if the AB1 meets AF2, they share the first one, and so on. After some mathing, we figure out that each sex has 288 other sexes they can mate with and reproduce, giving us a random chance encounter of… 56.8%, so it is actually better than you bisexed species of 50% chance of finding a suitable mate!
Kinky
Honestly here we are going into the real crazy. Just go nuts, more sexes, more ways, there are so many mathematical possibilities, ways to do it, and I am just going to check out here. Look to nature, get inspiration, and go nuts. There is no limit but your own imagination, and even I struggle here.
Sex determination
(Anne: Don’t you hate how men complain about their wives only giving them daughters and then divorcing their wives in search of a son when it’s the men who determine the sex of a baby?)
Thanks, Anne, for your very human-centric input. Yes for humans it is the sperm which is produced by males that determines the sex. In fact it is so for most, if not all, mammals on Earth. But there are many ways to deal with sexes and which of them an individual becomes. It is important to note that sex does not need to be a lifetime determined deal. But we’ll start there because that is where you hoomons are familiar with. Not like we Limaces are better, alright we are because we are herms, but we are still herms for life. I will be explaining under the premise of 2 sexes, regardless of how many you chose. All can be extended in some way to fit postduosexed species.
Genetic
Simple as they come. Genes determine the sex you get. We had the slime mould above with 3 different genes together determining it. For mammals, these genes are not randomly placed; in fact, there is a small set of them for you mammals. It is all located on what you call the Y chromosome. Yes, the X chromosome does not contribute anything to determining the sex. You might be wondering, “Wait a minute, XX is female!”, which is true…but if they contribute nothing, what does that mean? Yes, it means default is FEMALE! When nothing tells it to do differently, human development (and mammalian) defaults to female body and structure. That is why males have nipples as their development starts before the Y chromosome’s genes are activated and tells the body “HEY! This is going to be a male! Get working!” This is why XY females are a thing. Either the Y chromosome’s genes are defective and don’t do their job, or some other part of the genetics is defective that makes the body not react to the commands of the Y chromosome.
This generally results in females incapable of reproduction. The reasons are very plentiful, but like all things biological, it is never absolute. Interestingly enough, for birds, avian dinosaurs, it is the inverse. They have a ZW system, where females are ZW and males are ZZ instead. So it is the egg that determines the sex here. So if you make a bird-like people, or ZW system, then the complaint Anne complained about is valid! It is all the female’s fault! I am not 100% certain, but I think in these systems in general, the bodies default to male instead of female, and similar things arise here.
If you do a bisexed species with chromosomal determination system, which is common in vertebrates, keep in mind that, in general, XY refers to any system where the males have dissimilar chromosomes and females have similar chromosomes, and thus males determine the sex. ZW refers to when it is the opposite. They are not mammalian but avian exclusive names and systems.
Thermal
This one baffles me in why it exists. What is the benefit of this? Doesn’t it run the risk of getting too much of one sex? Well, it exists. This one is popular in reptiles, and it is the temperature of the egg, for lizards, during the embryo’s development that determines the sex. Some species have colder = female, others have colder = males. If you make species that are sapient with this, this would be a very cool way to show how different subtypes develop as they spread out from their original habitat. Imagine what the different phenotypes of humans would be like if temperature determined the sex. Those in the north would have developed over time a different temperature range than those remaining around the equator. Imagine all the horrors and conflicts you can do with this no matter how you do the system!
Ploidy
Ploidy! Such a funny word, a silly word. Ploidy in its simplest form is essentially “How many copies of each chromosome do you have?” For most animals on Earth, it is 2. The ploidy is 2. You are diploidal. You have 2 chromosomes of every type, one from your father, one from your mother. We are, for what I hope is obvious reasons, excluding sex-determining chromosomes due to them having different versions in order to have the job of determining sex. So in most species, this cannot determine shit on sex.
But of course, there are exceptions! Eusocial insects, ants, bees, termites, and such, tend to love this system to determine the sex. In general, it is like this: Haploid (having one version of each chromosome) individuals are male and can only ever be male, diploid (having two versions of each chromosome, just like you humans do) means they are female. An interesting fact that arises from this system is that while you humans are only 50% similar with your siblings (assuming same parents), for these insects, sisters (which are the majority of workers) have 75% relatedness. It is believed that with this high relatedness, it became more favourable for the sisters to work together and sacrifice their own reproductive success in order to help others, as they have more to gain from it evolutionarily than being selfish. This is beyond the fact that the colony will quite frankly torture them if they try to reproduce. It has been observed that ants that try to break this taboo that only the queen and princesses may reproduce and not the workers, and the workers are caught (where they are laying haploid male eggs only), other workers come, grab all their legs and just hold them, hours on end. Other ants come and relieve the holders of the duty and then hold the leg, and they keep on holding until the traitor is dead from dehydration or lack of food.
Imagine if human females could do this. Give birth to males through parthenogenesis, and only through sex with a male could they have daughters. This would be interesting in a story! Yes no?
Moar methods
Honestly, there are many ways more to do this that I cannot even imagine but I’ll gatling gun a few quick ideas for you to imagine
Radiation levels, similar to thermal
Humidity
Light levels
Diet during gestation
Actual conscious determination through the usage of hormonal glands
Internal cycles on the female, where the point in the cycle the egg is produced determines the sex.
(Anne: Pheromones, where exposure to the pheromones by an egg or carrying female determines the sex)
For fantasy, mana exposure!
(Anne: Also for fantasy, curses or blessings!)
As you can see, there are many possible methods, and this is not an exhaustive list–be creative!
Sex is not fixed
Get your minds out of the gutter! You are all such a bunch of perverts constantly fixated on sex 🙄 Not all species are born the sex they die as. Many species start as one and become another sex. This is often called sequential hermaphroditism. With this, there are in fact no hermaphrodites ever, but rather, well, as said, you start as one sex and later become another.
Protandry is when every individual is born male and starts reproducing as males. Later in life, when head honcho, female usually, leaves, is usurped, or whatnot, the male turns into female and takes on all roles related to it. Protogyny is when all start as female and later become male.
There are many reasons why this can exist: because you have harem-like structures, protection against inbreeding, and much else. Protandry is, if I recall correctly, commonly correlated with what you humans would call “inverse sexual dimorphism”, that is, females are larger, stronger, and protective. Protogyny is the opposite and is more familiar to you humans.
Imagine yourself in a society with either of these systems, all kids being the same sex, and then, as you get older, you change sex because of some trigger or simply just by age. What social implications would that result in? Why is no one doing this?
This is just one direction, what if… it can go back and forth? What if… wait… I have done this: the Tsxobjezn species.
Sex Ratio
If you have more than 1 sex, postunus-, then there is always going to be a ratio between all sexes. Evolutionarily speaking, being the less common sex is generally better because you have many more options of who to reproduce with and being of the more common sex is worse as you compete more for the few ones you can mate with.
This is why most settle for an even amount between all sexes. Even for different determinations of sex, this optimal position is very common. An obvious example that contradicts this fact is eusocial insects. Where well over 90% of all individuals are female, the rest are males and males generally do little beyond reproduction. Other exceptions are sequential hermaphrodites where the born sex is more numerous than the one they generally become. But they are rarely as extreme as eusocial insects.
The thing is, you don’t have to do either of these. You can do abnormal sex ratios too for the purpose of making it interesting. My beloved species Raixher (I might actually do my next practicum on them) has 3 sexes, but they are not ratioed the same. Their ratio is 1:2:3, which means for every primale, there are 2 midmales and 3 ultimales. I have yet to decide how they determine sex, but it is going to be genetic somehow. Why did I pick this? Besides it being interesting, ultimales (their closest one to your females), being more numerous and the more disposable and easier to take power, means I could make a matriarchal society that doesn’t feel forced. As for why evolutionarily it evolved? Reasons! I am allowed to just assume it worked out somehow, kadabra!
So yes, sex ratio is a way to make things more interesting as well. Make certain, however, it serves a function, Doylian or Watsonian. And sometimes it can just be “It’s cool”, as long as it fits in nicely.
Sexual polymorphism
When it comes to sexes, no matter what system of reproduction, no matter how many sexes, at least when it comes to large multicellular lifeforms, there will be obvious differences. Namely in the reproductive organs and everything related. It is a necessary component for reproduction to work. This is why generally this difference is boring and rarely talked about as something significant. It is of course very important for reproduction, but it is so obvious. Sexual polymorphism, or dimorphism on earth as you generally only have 2 sexes, so boring! Anyway, it refers to differences in the body between sexes that are not directly related to reproduction. Examples include but are not limited to:
Muscle mass: how much muscle does each sex develop beyond basic necessity?
Body shape: how is the body generally formed?
Fat content: how much fat does the body naturally retain if given a healthy diet?
Fat distribution: where on the body is fat stored and located?
Fitness displays: extra structures that serve no purpose other than to say “I am well!”
Maturity displays: additional structures to signal that one is sexually mature
Colouration, feather, skin, fur, scales: changes to signal the sex
Sex displays: anything that is there just to show the sex when the organ is not obviously visible
So, as you can see, it can be a lot. Most of these are rather innocuous and harmless to the survival of the individual, but for example fitness displays can, as the peacock males know, be so excessive that they actively harm your survivability. But if you can survive with them, you are a damn good fit! Some of these evolve for the purpose of displaying one’s sex at a distance, others evolve to serve a specific role in the group due to mating structures. For example, harem structures generally cause a huge increase in body size for males in order to defend their females from other males.
Human examples? Well, you have a softer body structure for females and a sharper one for males. Males have a lot of additional hair around the face for sex display. Females develop breasts–
Those serve a function!
Wow, I didn’t even get the time to say “I know what you’re going to say”! You are getting fast! Anyway, yes, but if you look at other primates, they don’t need that excessive amount of fat around their mammary glands and the like. It is believed that humans evolved breasts for two reasons: fitness indicator and maturity display. When breasts start developing, females are generally sexually mature, and the more energy they have to invest in their development, the more they can invest in potential children as well.
I am, of course, in no way advocating anything to be done with bringing up these developments in both male and female humans, as generally the initial onset of these developments of the body in humans happen when they are STILL CHILDREN! Just don’t go there, just don’t. It is believed, or at least thought, that the reason why the onset of puberty and the development of secondary sexual characteristics is so early these days is largely due to a huge amount of food and energy being available, and potentially other hormone-related things in chemicals.
You can be very creative in what characteristics each sex has beyond their organs to signal their sex. In my Raixher species, their vines (Their version of hair), actually indicate the sex. I will in my practicum explain it, but not here!
Sapience reproduction
So what do you do if you have a sapient species and want to get a little kinky and weird in how their reproduction works? Besides my usual advice of “Look at nature”, which I have partially done for you in this post, I would suggest doing these steps in order:
Are they land or ocean living? Most will be land, but the ocean offers many more options. Just take into consideration the issues with ocean civilisations… damn, another blog post. Or if you want to get extra kinky, do they live in the gases of a gas giant or Venus-like world?
Determine the number of sexes. If you go with standard 2, we are going mostly wrong for this guide here, but you can adjust other points.
If you have a postdual amount of sexes, are they chained in reproduction, or do they go by dual? Oceanic life allows an easier time for chained reproduction than land, which favours dual instead.
Once you get the number of sexes down and the general idea of their body, even if it is classical humanoid, think on where you can change and add things. Make it befitting of their role and history. Where would they develop differences that are based on sex?
Decide how sex is determined. If you want the baseline, just go genetic and ignore the rest.
Consider what the ratio between the sexes would be. Both what is needed to make a society you want and what logically works based on sex determinations and such.
Go to my future blogpost about society and sexes that I will link 👉 here when ready
Summa Summarum
So what have we learned here? That nature is crazy. Real kinky bitch if you ask me. And that we can spice up our own societies and species. I have hinted at how a different method of reproduction and sexes can and will alter how they view the world and relate to other things, something I will go into more depth later.
We can have many sexes, we can have different sex ratios, different polymorphisms, there are quite honestly so many options and imagination is what puts a limit on it. Make your species’s sex lives and beings as interesting and fascinating as possible. Earth might have settled on mostly a bisexed structure, but that does not mean you as a creator must do the same. Be interesting, be weird, be brave!
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Copyright ©️ 2023 Vivian Sayan. Original ideas belong to the respective authors. Generic concepts such as sex determination methods, sexual polymorphisms, polysexed species, and sexual changes in adults are copyrighted under Creative Commons with attribution, and any derivatives must also be Creative Commons. However, specific ideas such as Raixhe the species, Tsxobjez the species, and all language or exact phrasing are individually copyrighted by the respective authors. Contact them for information on usage and questions if uncertain what falls under Creative Commons. We’re almost always happy to give permission. Please contact the authors through this website’s contact page.
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