After the Vulcans and Romulans split by just looking at one how can you tell the difference? For example on one of the episodes a guy looks at Spock and says he is a Vulcan but how does he know he's not a Romulan?

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    Which guy, and which episode would help. Until Balance of Terror, no-one in TOS knows what a Romulan looks like, even the Vulcans at that point don't know that the Romulans and the 'non-Surak accepting vulcans' are one and the same. Vulcans and Romulans look identical Sarek, and the Roumulan Commander both being played by Mark Leonard. – Simon Bucher-Jones Dec 15 '17 at 13:32
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    Cut 'em open and count the rings. – Valorum Dec 15 '17 at 15:44
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    No, wait, that's trees. – Valorum Dec 15 '17 at 15:45
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    Context. I can't tell apart a wolf from certain dog breeds (and neither can a lot of people or film makers wouldn't be able to get away with stuff), still I would never say to someone: nice wolf! If it's with a person, it is a dog. If it is with star fleet, Vulcan – Raditz_35 Dec 15 '17 at 15:53


Prior to "Balance of Terror", most of the species in the Federation were only aware of one pointy eared, green blooded species. Therefore, any Romulan they met would instantly be a Vulcan in their eyes.

After "Balance of Terror", the majority of Romulans encountered were part of the Romulan Military (on board Romulan ships, wearing Romulan uniforms etc).

Similarly, Vulcans were generally encountered where one would expect to find a Vulcan (Federation or Vulcan starships, bases etc.)

Beyond that, there would be behavioral cues. For example, regarding Amabssador T'Pel:

The script for "Data's Day" ... says, "She is Vulcan, middle-aged, and has the cool, regal bearing common to her species."

Cool and regal are not Romulan traits by any stretch.

On some occasions, such as with Ambassador T'Pel/Sub Commander Selok, Vulcans and Romulans were able to pose as a member of the other species without altering their physical appearance.

  • Talok in the 22nd century
  • Selok in the 24th century
  • T'Paal in the 24th century

The only thing that these characters changed was their behavior, hairstyle and clothing so they would seem more Vulcan or Romulan as the situation required. Unlike Kirk, Picard, Data and Troi-no cosmetic surgery was necessary.

Let's not forget about Simon Tarses who was part Romulan but passed for Vulcan and was never questioned about it until the events of "The Drumhead".


In TOS "The Paradise Syndrome" Spock studies the ancient writing of the Preservers and learns to read it:

POCK: You prescribed rest, Doctor. The symbols on the obelisk are not words. They are musical notes.
MCCOY: Musical notes? You mean it's nothing but a song?
SPOCK: In a way, yes. Other cultures, among them certain Vulcan offshoots, use musical notes as words. The tones correspond roughly to an alphabet.

So Spock knows of at least two Vulcan offshoot cultures that use musical notes as words, and at least one that doesn't. These three or more Vulcan offshoot cultures may be primitive ones protected by the Prime Directive and studied in secret or full fledged members of interstellar society that Humans and Vulcans sometimes met. Presumably these Vulcan offshoot people dress and behave differently than Vulcans and so can be told apart.

Furthermore, "Journey to Babel" indicates the natives of Rigel V have a similar physiology to Vulcans and possibly a similar appearance, and possibly are members of the same species.

SPOCK: Doctor.
MCCOY: I see it, Spock, but that was a Rigelian.
SPOCK: Rigelian physiology is very similar to Vulcan.
MCCOY: Similar is not good enough. It's still experimental.

Thus the statement in Geewhiz's answer that:

Prior to "Balance of Terror", most of the species in the Federation were only aware of one pointy eared, green blooded species. Therefore, any Romulan they met would instantly be a Vulcan in their eyes.

Should be only partially accurate in the interstellar civilization of TOS.

  • You're not wrong. However evidence points to those offshoot cultures not being part of interstellar society. We only ever see two pointy eared green blooded warp capable species (Romulans and Vulcans, 3 if you count Remans). Also, the cultures we do see are almost universally identified as Vulcan, Romulan or Reman-nobody ever looked at a Vulcan and thought it was Debrune for example. This would imply that the offshoots are pre warp, extinct or intentionally staying out of interstellar politics. – geewhiz Dec 16 '17 at 17:48
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    Addressing the quote about Rigellians. Physiology and Morphology should not be confused. Physiology is the study of HOW the body works not what it looks like. Physiologically, Romulans and Klingons share similarities that make them good donors for one another but nobody would mistake one for the other. I don't think a Rigellian has ever been shown on screen but until one is, we can't simply assume they look Vulcan. – geewhiz Dec 16 '17 at 17:51

While not canon, the book "My Enemy My Ally" by Diane Duane has the following quote from McCoy, which gives a physiological reason.

The quote is discussing a plot to invade a Romulan station with the aid of Romulans (matter of honor), and having the Rihannsu act as Vulcans with each boarding group:

"They won't think that for long, Spock," McCoy said. "Remember, Rihannsu and Vulcan culture have been diversing for thousands of years...and most of the subconscious cues buried in their respective kinesics, their 'body language,' will also now be very different. A Rihannsu would know you weren't one, if he looked long enough, not from any physical divergence- but just from a wrong 'feel.'"

So basically, while a Vulcan may outwardly look like a Romulan, there are ways of walking, acting, talking that are endemic to any culture, and if a person does not fit that, they give off a wrong vibe to people of the culture.

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    There was a TNG episode (Data's Day) in which a high-ranking Vulcan in Starfleet was revealed to be a long-time Romulan spy. Also, in "Unification", Spock was pretty much able to wander around without drawing attention to himself. There are also the "ridged-forehead" Rommies, but for all we know there may be Vulcans with the same trait and we've just never seen them. – Emsley Wyatt Dec 15 '17 at 14:51
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    @EmsleyWyatt yes, I did not include the TNG items. And there are spies that are trained to pass themselves in other cultures/races. That isn't available to most people, as evidenced by people that basically shout "tourist" just by their dress and/or actions. – JohnP Dec 15 '17 at 15:07

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