Throughout Star Trek, Spock is referred to as having many Vulcan characteristics such as his pointed ears and inner eyelids. He is also stated to be half-human. Are there any human physical characteristics mentioned on-screen that he possesses that pure Vulcans don't?

Also, I am aware he did have occasional struggles with suppressing emotions, but, other Vulcans (namely pure Vulans), such as T'Pol and Tuvok have similar issues.

  • 1
    I'd maybe go with a title like "Which of Spock's traits come from his half-human side?" or something like that.
    – RedCaio
    Commented Jun 7, 2016 at 22:26

1 Answer 1


The only non-mental evidence of his human heritage mentioned in the "Physiology" section of his Memory Alpha article is a scene from the episode "Journey to Babel", in which his father Sarek needs a blood transfusion and there is the following discussion:

SAREK: My blood type is T-negative. Somewhat rare, even for a Vulcan.

MCCOY: Yes, I'd say that's rare.

SPOCK: My blood is T-negative, Doctor.

CHAPEL: We've run a number of blood tests on Mister Spock. It isn't true Vulcan blood either. It has human blood elements in it.

SPOCK: It should be possible to filter out the human factors.

MCCOY: Even you couldn't give that much blood, Spock. It would kill you.

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    Was not expecting a concrete answer, given how the character was created by adding attributes to a human actor. +1. Commented Jun 7, 2016 at 22:41
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    Ah, human blood elements, the worst kind!
    – Rogue Jedi
    Commented Jun 7, 2016 at 22:59
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    @RogueJedi I imagine Sarek thinking "eww human cooties!"
    – Criggie
    Commented Jun 8, 2016 at 11:31
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    When you start to think about it you realise that there is no way humans could reliably reproduce with Vulcans. At best it would be a one-in-a-thousand that he'd be born at all and you'd expect a hundred health issues to besiege him. Human antibodies would attack the Vulcan elements, and the reverse. If the brain used only Vulcan blood cells or only human blood cells, it wouldn't get enough Oxygen to survive. You'd also expect mental problems beyond a little trouble with emotional control, like instinct conflicts. You would need extensive genetic modification to make him viable. Commented Jun 8, 2016 at 13:09
  • 4
    @PointlessSpike: You're not...thinking scientifically about ST?! Commented Jun 8, 2016 at 14:13

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