We know that Klingon and Human DNA is compatible enough to reproduce (B'Elana Torres); same with Human and Vulcan DNA (Spock), and Cardassian and Bajoran DNA (Tora Ziyal).

Are there any examples of 2 humanoid species in Star Trek that are explicitly noted in canon as NOT being biologically compatible? (unable to produce a viable genetic offspring between each other with technological assistance as well)?

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    I have to VTC because this question is actually too broad to answer. There is an episode of Enterprise that posits some sort of hybrid creature descended from humans, Vulcans, and several other species, including some that Phlox had no point of reference for. We've seen a half-Betazed, half-human female impregnated with a fully-human child by a being composed of pure energy. We've see Trip Tucker impregnated, despite being a man, because Enterprise hired a Futurama writer. There is no adequate answer to this question. Commented Apr 6, 2014 at 8:08
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    In the TNG episode The Chase it turned out we were all related. So I presume we're all compatible.
    – Mr Lister
    Commented Apr 6, 2014 at 8:12
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    As @Richard said, Star Fleet doctors knows tricks to make incompatible species compatible. Jadzia Dax and Worf are the obvious examples. Commented Apr 6, 2014 at 9:15
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    ROmulans are compatible with Klingons - See "Birthright Part 1"
    – Valorum
    Commented Apr 6, 2014 at 9:17
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    This is a good question, but those who have closed it do have a strong point: this is very broad. How many species have we seen across the many different series of this franchise? Hundreds, the low thousands? I'm not going to vote to reopen.
    – John O
    Commented Apr 7, 2014 at 0:02


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