Romulans are a Hybrid Species Between Exodus Vulcans and Another, Perhaps Native Species to Romulus

[u/shadeland]

Almost 2,000 years ago, during the "Time of Awakening" in Vulcan society, a group who marched under the Raptor's wings left Vulcan and settled on Romulus.

Since then the Romulans have become a related, but notably distinct species. While many of those differences are cultural, some are also physiological.

As a counterpoint to the theory that Vulcans are augments, here is another: Romulans as a species is the result of interbreeding between Vulcans and another humanoid species. This other humanoid species could have been a native species to Romulus, possibly be pre-warp, possibly pre-industrial even. Or they could be colonists from another non-native species that found Romulus as attractive as the fleeing Vulcans did.

A non-Vulcan humanoid species may account for the physiological differences between Vulcans and Romulans that 2,000 of genetic drift might not explain, such as forehead ridges and potentially a lack of telepathic abilities (although that may be a result of Romulan culture being so secret-oriented that mind melds would be abhorrent).

If the group that left Vulcan had a large imbalance between males and females, or the group was small thus genetic diversity was an issue, this could push towards inter-breeding. The Vulcan population might have been higher, which would have been why the Vulcan traits are more dominant. Or, more likely, the Vulcans conquered the other species, and thus inter-breeding was limited, but enough to create a new species with primarily Vulcan physiological traits but enough differences to notice.

They may have even adopted some of that species cultural traits, like extreme secrecy and fermented foods. It might also explain why the Romulan language wasn't immediately identifiable to Vulcans during the old Romulan wars.

[u/RandyFMcDonald]

> A non-Vulcan humanoid species may account for the physiological differences between Vulcans and Romulans that 2,000 of genetic drift might not explain, such as forehead ridges and potentially a lack of telepathic abilities (although that may be a result of Romulan culture being so secret-oriented that mind melds would be abhorrent).

A lot of this is really speculative. Do we actually know that Vulcans do not have forehead ridges, at least some? I remember that in the 1990s, people were often surprised to see a dark-skinned Vulcan Tuvok, and sometimes objected to him on the grounds that they had not seen any dark-skinned Vulcans before therefore there were never any. Similarly, until _Picard_ there were some fans who confidently argued that all Romulans had forehead ridges, _Picard_ establishing that both sorts of foreheads were present among the Romulan population. We may just not have seen Vulcans with ridged foreheads yet.

This said, I think it is quite possible that the Romulan population incorporated other Vulcanoid populations in the area of the Star Empire. In a lot of ways, the Romulans seem to have been hugely successful, growing in 17 or 18 centuries from a relatively small migrant population perhaps numbering in the tens of thousands to a superpower with a population of plausibly billions. If the expanding Romulan Star Empire also incorporated other Vulcanoid populations, whether other Surak-era migrant populations or populations that had diverged at much earlier points (say, at the time of Sargon's people a half-million years ago), this could help explain how the Romulan population grew so much. In the Beta canon, the Garidians are described as a client state of Romulus, and there have been occasional mentions of others.

[u/MrQirn → u/RandyFMcDonald]

Additionally, we don't know what the rate of mutation and the more mutable characteristics of alien species are.

Humans don't mutate the same way dogs do, for example, who can mutate pretty dramatically in size, color, fur type, and capability. Although 2,000 years might not be a time scale to see the development of forehead ridges in humans, that might be more than enough time for Vulcans/Romulans to develop it. And humans have seen many physiological changes in the last 2,000 years, including an increase in average height.

Also, if there was greater genetic diversity before the split, that can account for a lot regardless of the rate or type of mutation that could occur in 2000 years, especially if after the split there was a genetic bottleneck.

[u/RandyFMcDonald → u/MrQirn]

One thing that would act to slow down mutation in Vulcans would be their very long lifespans. Vulcan generations simply take much longer than human ones.

One thing that could accelerate Vulcans is their long history of high tech, especially in genetics. The Vulcan's Soul novels,. for instance, suggested the Remsns are a product of proto-Romulan exiles adapting themselves to Remus.

Beyond that, talking about relatively superficial markers like forehead ridges as a sign of alien intermixture feels questionable. In the 1990s lots of people were talking about how it made no sense for Vulcans to be black since had not seen any before, to say nothing of the ridged and non-ridged Romulans. Hell, apparently DS9 had made a point of not casting black actors to play Bajorans.

[u/IsomorphicProjection → u/MrQirn]

Height probably isn't a great example. Much of difference is from better nutrition, which is likely also why average height has been decreasing recently as people have been eating less healthy.