In the SF world of Classic Star Trek, the Vulcans are an alien race which, surprisingly, is capable of interbreeding with humans despite vastly different biologies. The Classic Star Trek character Spock is a hybrid with this race -- half-Human and half-Vulcan.

Vulcans are known for their devotion to Logic as the guiding principle behind all moral and personal decisions, a philosophy similar to Zen Buddhism in its denial of emotions but different in that Vulcan philosophy prizes social duty whereas Buddhism views social duty as one of the worldly temptations which must be transcended to achieve detachment and the state of being known as nirvana. Vulcans are also mystics, as their telepathy provides them with verifiable scientific evidence of the soul.

Vulcan blood systems apparently use hemocyanin instead of hemoglobin. Hemocyanin is copper-based instead of iron-based like hemoglobin and found only among mollusks and arthropods on Earth. However, whereas hemocyanin is blue not red, Vulcan copper-based blood is green.

In Star Trek, the Vulcans fill the SF/fantasy niche of the elder brother race.