I'll offer the one piece of evidence I can think of that might support the existence of Cardassian/human hybrids: In the TNG episode "The Chase", it was revealed that an ancient precursor species seeded many worlds with their own DNA, and that contributed to the development of humans, Vulcanoids, Klingons, Cardassians, and others. Since we know that humans and Vulcanoids can interbreed (Spock and Sela), humans and Klingons can interbreed (K'Ehleyr, B'Elanna), Klingons and Vulcanoids can interbreed (Ba'el), etc, it seems reasonable to think that humans and Cardassians could interbreed - and this is possibly supported by Seska's attempt to impregnate herself with Chakotay's baby. (She apparently had some aptitude in both science and engineering - but was also nuts, so take that for what you will.

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