I was thinking for ideas for new species for the planet I'm currently worldbuilding, and it occur to me if there could be a species (humanoid) where everyone looked exactly the same, and if this could happen naturally.

Thank you so much.

  • $\begingroup$ Does "look the same" also mean having the same gender (assuming they have gender) and the same genetics, or is it enough that they just look the same from the waist up? $\endgroup$
    – Priska
    Commented Dec 1, 2019 at 5:23
  • 1
    $\begingroup$ Can I edit your question to say “species” or did you really mean “race”? The existing answers lean toward “species” interpretation. $\endgroup$
    – SRM
    Commented Dec 1, 2019 at 8:10
  • $\begingroup$ This is the premise of the short story “The Barbie Murders” by John Varley. en.wikipedia.org/wiki/The_Barbie_Murders $\endgroup$
    – Mike Scott
    Commented Dec 1, 2019 at 21:02
  • $\begingroup$ @MikeScott: The "Barbie Murders" happened in religious sect that made all its members under go an operation to be made to look like Barbie dolls. A better example would be Joe Haldeman's "The Forever War." The "enemy" is a species of natural clones. Humanity eventually makes itself into a species of clones (in male and female versions) that reproduce sexually but still maintain the same genetic make up (all individuals are identical despite being born through normal sexual reproduction.) $\endgroup$
    – JRE
    Commented Dec 2, 2019 at 16:01

5 Answers 5



There are two layers to physical appearance - genotype and phenotype. Genotype is the written instructions for appearance based on the DNA. This is where terms like 'heterozygous' come into play. It's very important, and theoretically you could have a race where everyone has the same genotype for physical appearance. I'm not sure why it would evolve as such, because there are several problems with it, but it's possible.

Phenotype? Not so much. Phenotype is the physical expression of the gene, and is affected by many factors, among them things like pressure or heat. In the case of developing creatures, often there are slight variation present during growth conditions, i.e. baby in the womb and even the maturation process of childhood - a serious injury could affect something of this nature. Phenotype variant can never be perfect - at best you're looking at something akin to a race of identical twins.

And identical twins do not have identical appearances. True, it's very hard for someone unfamiliar to spot the difference, but take this from personal experience with a large number of identical twins - it's very easy to tell the difference with enough experience, and it gets easier with every new pair of identical twins. You'll wind up with a race of practically identical individuals, but where all of them are essentially masters at picking up on even the most minute of differences.


Yes, it is possible.

Physical appearance is not controlled just by genes - you can always get a facelift, or you can have your face distorted by an accident - but genes play a major part of it. If there is very little genetic variation in the population, people will tend to look all the same.

There will be those who say that little genetic variety is bad for populations on the long run, but mostly people are confusing little variety with inbreeding. Aphids and a lot of reptiles species reproduce through parthenogenesis, which sounds like making love in the greek Parthenon while listening to Phil Collins songs but actually means females reproducing without any participation from males. This means the offspring are practically clones of the mother and variety happens through mutations.

If your fantastical species (please don't call it a race) reproduces through parthenogenesis, most likely everyone will look (and smell, and sound) mostly the same.


Such a race would have interesting implications.

One really tricky bit of this is defining "looks the same." I'm reminded of a story I heard of bars with a large Asian customer base hiring Asian bouncers because the white bouncers had more trouble identifying one customer from another by facial features. The distinctions in the Asian facial structure were more nuanced than one experienced growing up in predominantly white communities. What "looks the same" to one individual, raised in one culture, may have distinguishing characteristics to another individual raised in another culture.

This can be taken to an extreme when we leave the concept of H. sapiens race behind. Consider ants. While many ants of the same species "look the same" to us, many ants can distinguish nest-mates from non-nest-mates by smell. To them, these individuals are easily distinguished. To us, they might as well be clones.

So the difficult case to achieve would be where individuals of that species/race cannot distinguish each other by appearance/smell/etc. The advantages of being able to distinguish individuals would be so profound and widespread that you'd need to come up with a good reason why they wouldn't do so. (If I started listing all the reasons it is advantageous, I'd quickly find out whether Stack Exchange has a maximum character limit or not, there's so many)

The reason cannot be sexual. The entire purpose of sexual differentiation is, well, to differentiate. It would never lead to indistinguishably. Or would it? Consider a race which has somehow reached its ultimate state. There is no better-ness for it to achieve. In such a case, being able to identify flaws would be a big deal. Everyone may look identical except when things go wrong, in which case they would be quickly dispatched for the greater good of the community.

Our own bodies provide another possibility. Our immune system recognizes antigens on our cells to provide a sort of class based identity. Some antigens appear only on one type of tissue, so they provide some identity (perhaps as "pancreas cell"), but I am unaware of any bodily process which recognizes an individual cell via this means. No cell goes around wearing the name tag "Heart muscle cell #39284432".

In such a system, identity has no meaning. I would expect similar in your fictitious species. It would think nothing of the slaughter of ten thousand bodies than you would think of the skin cells you slough off when you scratch an itch. They would merely be book-kept in terms of raw resources needed to produce another ten thousand.

And like in the body, I would expect this class based existence to provide anonymity only in some classes and not others. While in theory neurons in our brain are fungible, with the ability to substitute one for another, they form dense interconnected webs which become quickly individualized. They, in effect, grow their own identity, differentiating from others. Take them out of the system, and they may be hard to identify, but within the system there are clear patterns. I would expect similar in your culture. Any identity deemed worth having would be maintained in the form of relationships which exhibit this uniqueness. Phrases such as "family is forever" would take on a depth to which the human phrase pales to compare with.


As with any biological property this would only happen if it is sexually attractive and biologically preferable to be 'exactly the same', but it won't last long and the concept of 'race' is misleading to say the least

Many species evolve distinctive features because they are sexually attractive to mates - look at the signal theory for more detail. But the reasons would be:

  • Having differences send signals of strength, agility or other desirable traits to mates who can choose their partners
  • Differences indicate separation from one mate to another in order to distinguish themselves. Uniqueness is in itself seen as advantage or physically attractive quite often.

However in your humanoid 'race', it is conceivable that differences are instead seen as negative indicators of compatibility, and send the wrong signal. Perhaps distinctiveness is an indication of disease, of failing beauty standards or not satisfactorily achieving desired attributes in a mate.

This could be conceivable if the following conditions exist:

  • Distinctiveness is achieved in an intellectual, status, or otherwise non-physical, way to distinguish preferred partners
  • Social systems are very much based around ideas of physical uniformity and consistency, instead of physical individuality and distinctiveness
  • Environmental factors, such as increased melatonin production due to higher sunlight exposure, are reduced such that physical appearance does not get influenced by such factors
  • Genetic factors, such as eye colour, red hair etc. are already recessed such that their occurrence is very minor.

Keep in mind that this 'race' would eventually succumb to disadvantages of this approach and may not survive the test of time. This is because:

  • a smaller genetic pool, the lack of variety in genes even though only physically applicable, promotes genetic disease and regressive genetic trends. Randomness and 'mixing' actually promotes resilience and healthier individuals.
  • such societies that put such emphasis on physical consistency often do not put much emphasis on creativity, individual ideas and opinions, and as such tend to not progress in this way often
  • ideas of 'race' are old ideas that often brush over the complexities of human societies and genetic biology. Many scientists have coined the creation of the classification of 'race' to be one of the major errors of the last couple of centuries, resulting in many misconceptions and over-simplifications that lead to often twisted and nonsensical arguments. The definition of 'race' is still not agreed upon has not (in fact, cannot) be formalised, and in fact many scientists consider it misleading and put forth that the term should not be used at all or in any modern context.
  • $\begingroup$ In works of fantasy, the word "race" does not mean what it means in the real world. Dwarves, elves, and men are different fantasy races. Whether this specific meaning leans more towards "species", "subspecies", "morph", or "lineage" is never explained, and it would be unseemly to attempt to. Genres have conventions. $\endgroup$
    – AlexP
    Commented Dec 1, 2019 at 8:32
  • $\begingroup$ @AlexP Understand - although the tags 'scienced-based' 'biology' and 'genetics' are present, it is prudent for the definition to be worthy of scrutiny. $\endgroup$
    – flox
    Commented Dec 1, 2019 at 12:39

I could imagine some kind of hive species where 99% of the population are "workers" and look the same. Only the queen and drones may look different. They could even look so different that space travellers wouldn't recognize them to belong to the species.

Or another idea: They are human-like and depend only on artificial insemination or some kind of cloning. So the entire population is female and has the same genes.

Both ideas share the same problem. The individuals are only as equal as identical siblings. They may be hard to distinguish, but they will be distinguishable. Of course they have different jobs, some may have more muscles than others, they have different ages etc.

If you really need indistinguishable persons, they have to be robots (and even then they may be built different, based on their tasks)


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