I was thinking about the Star Trek the original series episode "All Our Yesterdays", where the enterprise crew are thrust back in time to separate time-periods of the planet Sarpeidon.

Spock went back in time to an ice age, and fell in love with a woman named Zarabeth, as part of his biological regression. Violence among Vulcan's was common at that period, but in biology the purpose of violence of that sort is about reproduction and selection.

Spock himself is proof that Vulcan's and humans can have viable offspring.

Did Spock introduce Vulcan DNA to the Sarpeidon gene pool? Would this qualify as a violation of the prime directive? Given how amazingly technologically advanced the civilization was, could that level of advancement be correlated with introduction of Vulcan DNA into the gene pool?

Update: In the novel, Spock and Zarabeth had a son. https://memory-alpha.fandom.com/wiki/Yesterday%27s_Son

1 Answer 1


Highly unlikely. Zarabeth was exiled to the ice age - meaning, her location in both time and space was deliberately chosen to keep her permanently isolated from anyone else of her kind. One has to assume the ones who exiled her reserved a good amount of time before and after her arrival, in which no-one had ventured anywhere near her; in fact, it is quite possible she was marooned in a time actually preceding the evolution of her kind [which is just the sort of thing the dictatorial bastard who exiled her would have done]. In that case, even if (as you say) she had a son, that son also would have spent a life in exile, so his genes couldn't have become passed on into their gene pool.

  • My understanding is that the ice age was only 5000 years before the present time. Evolution can't do much in that period.
    – Paulie_D
    Dec 5, 2018 at 16:03
  • 3
    In the strict sense of evolution as a change in allele frequency in a population, even 750 years is plenty of time (1 in 200 men direct descendants of Genghis Khan).
    – Gaultheria
    Dec 5, 2018 at 17:15

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