Yes. Is it stated outright in an episode? No. Is this how Trek novels interpret it? No. But I'm still sure.
After all, no episode contradicts this model.
According to MA, Kriosians are from Krios Prime while Trill are from Trill.
And Riker is from Alaska, and he can still be host to a Trill. That is, if "Trill" is the slug. But any inhabitant of planet Trill can be called "Trill", be it a slug, a Kriosian host, a Terran host, a Klingon host, an unjoined Kriosian, an unjoined Terran, or an unjoined Klingon - as long as said individual (or joining) has Trill citizenship. Worf is Terran, too!
The MA page for Kriosians never mentions the word "Trill" while the MA page for Trill refers to them as the humanoid species that can serve as host to a symbiont.
That's valid speculation. But it's no more valid than mine. In the episodes, it is never defined who is the "actual" Trill, and it is never claimed that the hosts are a native species to planet Trill. For all we know, the hosts are all immigrants, and the slugs maintain a policy wherein only Kriosians or related good-looking species are allowed in, and only a select few of them are accepted as hosts, while the others have to pander for the joined pairs without even getting a slug.
While Trill and Kriosians look the same, I think they're different species.
Well, if Trills are the slugs, then yeah.
I mean, with as many species that look exactly like humans, it's not hard to imagine finding two different, but similarily spotted species.
Indeed. And it would not alter my theory much if the hosts preferred by the slugs were of some other species besides Kriosians. One might even argue that there are distinct differences between the spot patterns of the two species - but one would then have to overlook the differences between the spots on Jadzia Dax in different episodes!
In any case, the Trill humanoids seem to have the market cornered on symbionts.
Or vice versa. Joined pairs seem to be the masters and deciders on planet Trill, and the unjoined humanoids work for the pairs and the slugs and even eagerly compete for the "honor" of that servitude. It would seem clear that the slugs actually dictate the joining market.
My guess is that both the symbionts and the humanoids evolved on the same planet and for millions of years of evolution, enjoyed a symbiotic relationship before ultimately separating and evolving into the current symbiotic relationship. That would explain similarities in cell structure that would allow for the apparent lack of rejection (immune response) toward the symbiont.
My guess in turn is that the slugs are predatory opportunists. They originally used their electric shocks to disable large prey for consumption. At some point, they found out that living inside the carcass was beneficial. Later on, they found that living inside a still-living victim, and controlling it with electric shocks, was even more beneficial. And eventually the degree of control got refined so far that the victim could be made to do the slug's bidding. At which point the slugs could reach out big time, and start influencing their prey through captured prey bodies.
By the time the first humanoids arrived on that planet, Trill evolution had long since reached its pinnacle, and the slugs had no trouble capturing their first sentient prey. From there, it was only a tiny hop into making the prey believe that it should volunteer for capture, just like previous nonsentient prey was already volunteering. A bit of additional experimentation, and the slugs found the perfect hosts - they convinced a bunch of Kriosians or similar species to take residence on the slug homeworld and start building an infrastructure for them.
As for large body cavities in the Trill humanoids? It's possible. Evolution is pretty efficient and doesn't lend itself to wasted space, but at one point I assume there were enough symbionts for all the humanoids, until the Trill humanoid population exploded and they had to make up rules for getting a symbiont. Or perhaps the Trill organs can be rearranged and squished but still function when there is a baby in the womb.
It might well be that the Kriosians or near-Kriosians have good body cavities for this purpose, or give birth to much smaller babies than for example humans do. But it might also be that slugs discourage pregnancies on joined female hosts, and that the children that the previous female hosts of Dax had were all born before the joining. The symbiont would still carry the memories of motherhood, as it apparently is capable of absorbing even those memories of the host that the host has accumulated before joining.
Was there not a civil war on Trill that gave us the symbiont relationship?
Yeah - in an absurdly convoluted novel. If one is willing to believe that not all spotted humanoids are Kriosians, then one wouldn't easily accept the premise of that novel...
Timo Saloniemi
