Well, first clarification, it could sound contradictory "I want a humanoid shape that not looks like a common human", well for this reason I thought necessary say what I consider "humanoid", simply a stickman shape, you know just a head above a neck of part of a "vertical" column connected with a hip with two legs under, sure we can change this a few, for example add or remove arms or change the posture but this in general traits is what I will consider humanoid.

There is already similar questions but I could not find this specific, something like viability of humanoid non primate humanoids" or What will the abdominal muscles of non-primate humanoids look like? and a little bit less related with facial musculature of humanoid reptiles

So I am gonna explain, the human sexual dimorphism characteristics which I want discard.

For males is easier, just problems with muscle and fat distribution, for example (till where I know) mammals have a bigger concentration of fat and muscle at the scapular girdle, that permits the hump from bison, the strong for felids are the arms and pectoral muscles from apes, in difference with birds (dinosaurs had this concentration at the pelvic girdle) that have a very different distribution or amphibian and reptiles that are very uniform with this.

The problem is bigger with females, usually fantasy artists just add breasts without nipples and the curvy body shape caused by the fat the hips. So this give two options or justify why these characteristics are present or find other way to have sexual dimorphism.

First I will mention why the breasts and hips are not an option (till now) if I want something more "realistic", so the secondary function, at apes the growing of the breasts and the hips is an indicator of ovulation then for humans is an indicator of a constant ovulation, but this happens for the primary function, lactation, indicating a good health for provide the breast milk to the babies, something that comes hand in hand with a suitable mouth of the young to be able to consume the food without harming their mother.

So maybe I can let this happen for other mammal humanoids, but not for snake-women, "mermaids" or "harpies" and I honestly don't know how to denote that they are different from the males of their species. I don't think that add breast can have sense without the initial presence of nipples and with the hips I said I do not know how change the fat and muscle distribution keeping some of the most interesting characteristics.

The first option that I will mention is justify a reason for why this animals developed "human-like breasts and nipples", not my favorite, but I saw a very interesting justification at the anatomically correct arachne, the pluckedkiwi's answer in which explains why this arthropods evolved for a convergent shape with humans but for very different reasons, removing the secondary use for breasts and using very different structures for nipples. Anyways this still needing many other characteristics.

And the other option is find other visual/anatomical characteristic that can show which is the male and which is the female, there are some examples like different colors (like paradise birds or peacocks, maybe are not for reptiles or fishes) or sizes, this last I thought is ambiguous. And I will not like something like pokemon's "gender" differences, like "oh yea, males have two black lines at the nape and the females just one".

So in short what I want is:

  • Should be an anatomical feature.
  • A way to difference between female and male humanoid animals.
  • In this case just for reptiles, amphibians, birds and fishes.
  • Should be visual enough notorious for not be explained many times.
  • Alternative way, a some scientific justification of why keep the human characteristics (breasts and hips principally or pectoral muscles).
  • Keep the majority of the most notorious characteristics from initial species, for example flying for birds or swimming for fishes
  • 1
    $\begingroup$ Maybe this question can be reduced to "Why non mammalian animal humanoids would develop human breasts?" $\endgroup$
    – Drakio-X
    Dec 13, 2020 at 16:08

2 Answers 2


There is not a universal body shape or features other than genitalia to associate the difference between males and females. In the animal kingdom for may species the female is larger than the male so body size cant be taken as an obvious way to differentiate between the genders.

As humanoid qualities will be easier for your audience to recognise and associate with it may be best to take the obvious male and female proportions or features as non humanoid characters can sometimes be hard for people to understand and relate to.

The most notable quality of females or associated with femininity is sleek and slender bodies, where as rough and large creatures are often associated as male qualities. Without giving a back story to each species or showing their social interactions to explain why the females are muscular or larger and display dominant behaviour over the males, giving them associated human female qualities like slender but shapely bodies will be what your audience will be able to relate to understand.

If you are having difficulty when designing, look at different creatures and choose for yourself which creates seem very female or very male, or disregard human standards and give enough story to explain why the females and males have the body shapes they have.

  • $\begingroup$ Yeah, it's really depends on what you are trying to accomplish - if it is purely for realism sake - there's many real life animal species that one can drew inspiration from. But if the reader's ability to distinguish females from males at a glance is important or valued - yeah, there's very few options really besides giving females slender bodies an\or hips with boobimitators. And sometimes even going the "cliche" route isn't enough - I gave my alien females slender bodies and widest hips (Though no large chest bumps) - yet readers of my comic still mistake their sex sometimes. $\endgroup$ Dec 14, 2020 at 1:15

Big bland-colored males, small colorful females with Spines, frills, Feathers:

So in nature, you often have one gender bigger than the other, and one gender more colorful than the other. This is because one gender needs to draw in the other for mating, and one is likely to have a high metabolic load to care for offspring. So depending on how you want your species to look and work, make one fancy and the other big.

Think of the peacock. There is a lot of effort put into males showing off to females. In nature, males are more frequently the gender trying to lure in females to mate with. This can be color, or physical differences, or behavioral differences (like males breaking out into spontaneous dance to show off to females).

If one gender is more likely to assume high demands on themselves to raise offspring, size can matter. If you are going to produce lots of eggs (or have a live birth of a more formed offspring), you need to be able to handle an acute metabolic load. If you guard eggs (or hyper-vulnerable young), you either need to be able to not eat for a long time (often starving to death), or you need others bringing you food (maybe that other gender...). If you need to fend off predators, it's better to be bland, not flashy so no one sees you (and possibly big and powerful enough that predators don't want to mess with you).

Since you want the genders to kind-of parallel humans in appearance, make males egg guardians. Males are responsible for preparing homes for children (eggs) and fighting off attacks on the villages. Females want males that have nice places. Females convince males to mate with visible displays, they stay in relationships long enough that the male is certain the eggs are his, she lays the eggs. He is big, bland, and powerful. She can increase the likelihood of her children surviving if she gets food to support them.

Muscular males are bigger and more powerful. Heavy work and agriculture are products of villages of males banding together for mutual support. Females can have visible displays that may not have practical use but are enticing to males (like structures resembling breasts).

If you want to be creative, the females are the negotiators for the species and engage in non-reproductive sex with human males to get deals, secure personal relationships, etc. because in this model the females are more likely to be the 'promiscuous' gender (like human males). Thus being attractive to human males might be a survival advantage.

  • $\begingroup$ Females invest energy into developing eggs or young. Males are vehicles for genes to compete with each other. You can have males that are chosen by the females - these males would have attributes attractive to the female. You can have males that fight each other and the winner gets the females. These males will have characteristics that make them better able to fight their own kind. $\endgroup$
    – Willk
    Dec 13, 2020 at 21:56
  • $\begingroup$ You could have males that are dangerous to females and young that are not their own. Females in this species would have attractive characteristcs such that males mate with them and then do not attack them or their young, which might possibly be the young of the male in question. It is left to the reader to ponder how humans fit into these groups. $\endgroup$
    – Willk
    Dec 13, 2020 at 21:56
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    $\begingroup$ @Willk There are a thousand variations that can be proposed, and consequences for behavior for each. I was thinking of birds, where there are some interesting variants for roles (like penguins, for example). $\endgroup$
    – DWKraus
    Dec 13, 2020 at 22:41

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