- Romulans are the original species. Vulcans are Augments. The Vulcan/Romulan Schism was a result of differing views on genetic engineering.The logical faction believed enhancing their species was the logical thing to do, while the other faction viewed it as an abomination. This explains the genetic differences between Vulcans and Romulans, including the great strength possessed by Vulcans.
Interesting... Interesting... I actually read something similar in an old Best of Trek book... Like the Preservers grafting their DNA into the Vulcan species... We normally perceive Romulans as being "weaker" than Vulcans because, well, they settled on Romulus which has a lower gravity than Vulcan and, of course, they weakened in their long voyage there from Vulcan (losing their telepathic skills among other things)...
So we end up with Captain Kirk in "The Enterprise Incident" Easily taking out a couple guards with a quick punch and slap here and there...