There will be a poll at the end of this meta. You will be able to vote for different guesses by number. Please finish reading the meta before you vote.
By the time John Crichton gets sucked down his first wormhole in 1999, there are at least two human-related species waiting at the other end: Sebaceans (many of whom look indistinguishable from humans, others of whom have alien pigmentation) and Intirons (Jool's people, with the mood hair and vertical forehead ridges). Some other species may fall into this category as well: For example, John mistakes the Sykarans for Sebaceans because of their human-like appearance.
As season 4 and the sequel miniseries reveal, both Sebaceans and Intirons , at least, derive from human stock obtained from Earth by ancient Eidolons around 27,000 years ago. With significant genetic modifications, Sebaceans proved to be excellent enforcers, and many of them still serve in the "Peacekeepers," although at least one major independent colony has achieved and maintained independence in the Uncharted Territories. Along the way, they have lost their origin story; none of their peers seems to have a recorded history extending back to the Eidolons' reign, either.
Intirons rarely, if ever, join the Peacekeepers. Peacekeeper High Command frowns on producing interspecies reproduction, and non-Sebacean applicants must obtain a waiver in order to join. Jool even dismisses Sebaceans as "intellectually suited to carry weapons and die marching in formation"-- presumably not an opinion she has of her own people.
This raises a number of questions about whether Intirons and humans diverged as a result of Eidolon manipulation or other evolutionary pressures, why Intirons did not remain in Peacekeeper service, and how widely Sebaceans diverge from one another. It's even unclear if Sebaceans and Intirons are different species by our scientists' most common standard, that is, the ability to naturally produce healthy, fertile hybrid offspring. After all, Sebaceans and humans have no interfertility issues: Not only does John impregnate Aeryn Sun the old-fashioned way, but his genetic compatibility with Princess Kitralla is a major plot point of mid-season 2.
If Sebaceans, Intirons, etc., really are that distant, then either the Eidolons must have worked in most of the genetic tweaks, or the extraordinary environmental changes that their ancestors experienced must have caused far faster physical changes than have been found in any hominid population on Earth. For comparison, few scientists put the date of the human-Neanderthal (or Homo sapiens sapiens-Homo sapiens neanderthalensis, for those who view both groups as subspecies) later than 500,000 years ago. (X) (X)
There are a number of possible explanations for the level of variation that we see:
Theory 1. The Eidolons created multiple highly divergent cultivars from a wild-type human stock. They kept the one that worked the best, and left the others to colonize suitable environments.
A. The Eidolons themselves altered humans, Intirons, and perhaps some other groups until they were no longer naturally interfertile, or at least would experience lower fertility when paired across species. Genetic manipulation also explains the different appearances of Sebaceans and Intirons.
In this take, the Eidolons' manipulations seem, well, manipulative, but they might have been good enough at it to avoid causing serious hereditary illnesses. Even if the Intiron, and perhaps other, cultivars didn't suit the Eidolons' purposes, they were probably healthy enough, and were given enough resources to prosper.
B. The Eidolons didn't have any interest in creating multiple species. Sebaceans and Intirons only diverged after an early proto-Intiron group left the PKs. Exposure to differing gravities, radiation levels, microbiota, etc., caused the differences.
Now, as noted above, 27,000 years isn't that long in the scheme of human evolution. It's longer than H. sapiens has had blue eyes, but it's short compared to the development of, say, human hearing or human teeth. (X) (X) (X) It certainly isn't long enough to impact two groups' interfertility, as shown by the ethnic admixtures that almost invariably developed on Earth whenever long-separated human groups encountered one another.
So, if Intirons and Sebaceans really are too different from one another to produce healthy, fertile offspring together, and the Eidolons didn't make them that way, the proto-Intirons must have gone through absolute hell to direct such rapid adaptations. We're talking an "only a tiny percentage made it" level of evolutionary pressure. Which I guess would explain why we see so few Intirons over the course of the show.
Theory 2: The different species created by Eidolons are really more like subspecies. Maybe an adaptation/alteration here and there helps with specific circumstances, like crossing through strong radiation belts or incapacitating enemies with high-pitch hearing, but they're naturally interfertile, and their offspring (unlike, say, Scorpius) aren't going to be worse off than both parents.
I admit, I'm biased toward this one. I find it funny to imagine the PKs and Jool's old sorority sisters going through hundreds of microscopes to get rid of whatever defect is making them see DNA matches. Then there's the part where even Sebacean Peacekeepers look more varied than Earth's humans: Look at Grayza's blue-contoured skin, or the hair colors on Scorpy's nurses. If they had to admit their old species line was arbitrary, where would they put the new one?
Vote for your theory
1A (Deliberate, dramatic genetic manipulation)
1B (Extreme natural selection at play in discarded science-project people)
2 (The differences aren't large enough to need much explaining)
3 (Something else that I will now share with the class)
