Last night I was blowing up potatoes with fireworks and got some up my nose. I sneezed many, many times following that.
For the record, exploded potato mixed with gunpowder is downright caustic.
So, following multiple sneezes, I quipped, “Man, I am sneezing like a pregnant Bajoran.” Much was the laughter.
But it led my oldest to ask, “OK, I forget why Kira had to carry Keiko’s baby but it happened. But could it happen?”
Yes, we’re nerds.
But it raises an interesting question. Could a cross-species gestational implanting work? Human sperm and ova combined and then nurtured to viability in another specie’s womb? Yes, the issue in DS9 is larger, given that it’s not even different species but an entirely different ecology and evolutionary system but I think it applies locally. Would another species provide the right environment, nutrients et al for a human embryo to grow and thrive? Or is there something about gestation that is species-specific? If so, how?
I can’t imagine it hasn’t occurred somewhere. Not with humans but with other domesticated species. We’ve certainly done enough to our animal partners that I’d be surprised, frankly, if it hadn’t somewhere.
If it has happened, what’s the furthest apart that it has occurred. I don’t think anyone would be surprised if a dog could carry a little of wolves. But what about more divergent spots on the tree? Could a cat carry an otter? Or an elephant a rhino?
That’s actually a major issue with the idea of de-extinction. In the original Jurassic Park novels, they coast over this issue – InGen acquires a company that developed a patent for artificial eggs that they use to grow the dinos – but reality is far more complex.
For example, crocodiles and turtles determine gender based on the temperature of the eggs, and this process is so sensitive that eggs laid near the edges of the nest turn out one gender while eggs in the middle of the nest are the other. And climate change is messing those outcomes up.
There are other factors to consider. You would die without your microflora – the unique array of bacteria that live in your gut and and in digestion and other processes. A lab grown tyrannosaur would have no microflora, and neither would a human fetrus growing in an alien womb.
Anyway, in-universe most humanoids are derived from a panspermia event engineered by ancient aliens thus explaining why seemingly every species can reproduce with the others.
That essentially reduces the question to real-life interspecific pregnancies, which as already indicated, have been lightly experimented with but, as a research field, is still looking for a practical question to answer.
And explains why all of the races are just slightly differently colored Humans with odd bits of cartilage in their faces. Like they were designed in some kind of contest where the ancients had really tight requirements on being bipedal humanoids with similar features while allowing only cosmetic changes and a different disposition. The Vulcans/Romulans are about as different as it gets with green blood.
The Wikipedia article I linked to gives a number of examples that have been done successfully, including:
Bactrian camel carried to term by a dromedary
Gaur (Asian bovine species) carried to term by a cow
Deer mice carried to term by white-footed mice
Goat carried to term by a sheep
The article also gives the panda example which manson1972 noted (panda fetus carried by a domestic cat), though it appears that that was unsuccessful, due to the surrogate mother cat dying from pneumonia during pregnancy.
Microflora is not only in guts but all over body. Todays practice on cesarian section is swab the vagina of the mother with clean towel and immediately after the baby is cleaned swab them with the towel. This way the baby gets the same microflora they would have got if the bitrth had been natural.