How many alien species are compatible with humans?

Question

In the various incarnations of Star Trek across the decades, there have been some important characters who are half-human, one of their parents being an alien:

• Mr Spock, from TOS, is half-human and half-Vulcan
• Deanna Troi, from TNG, is half human and half-Betazoid

Which got me wondering: how many such pairings are possible in the Star Trek universe?

How many alien species are known to be compatible with humans?

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For the pedants and nitpickers:

• "are known to be compatible" means "have produced offspring at least once"
• this is about reproductive, not sexual, compatibility: if Kirk had sex with an alien, it's not enough to qualify that species unless she bore him a child
• yes, this is a list question, but it's a finite and clearly scoped one.

Answer 1

In addition to your examples, on screen there are:

• K'Ehleyr and B'Elanna Torres: each half Human, half Klingon.
• Naomi Wildman: half Human, half Ktarian.
• Sela, who is half Romulan, half Human, and Simon Tarses, who has a Romulan grandparent.
• An unnamed boy from a possible future in Enterprise: E² who is depicted as a descendant of the Denobulan Phlox and a Human crew woman.
• Karyn Archer, also from E², who was descended from Human and Ikaaran stock, as well as from two unnamed species.
• Daniel Kwan: half Human, half Napean.
• Linnis Paris, from a possible future in Voyager: Before and After: half Human, half Ocampa.
• Bethany, who had a Skagaran grandparent.
• A corpse from Enterprise: Future Tense: half human, half Terrellian.
• Yedrin Dax from a possible future in Deep Space Nine: Children of Time: part human, part Trill host.

I have omitted several known descendants of the above individuals, as well as less prominent characters who provide examples of hybrids with the same species listed above.

There are several other borderline examples: melding of species which did not imply biological reproduction, and so forth. For a more exhaustive list of inter-species hybrids, consult the Memory Alpha Hybrid page, which I consulted heavily for this answer.

Answer 2

Another example is the pilot of the starship from the future in ENT 'Future Tense'. Phlox identifies that the pilot was human, but also had Vulcan and Terrelian DNA, showing that humans are probably also compatible with Terrelians.

Answer 3

1. Cardassians and Bajorans
2. Kazon and Cardassians
3. Seska believed it was possible for a human and Cardassian to have a child.