Where to draw the line is arbitrary but breeding for even one or two traits can be extremely time consuming
How time consuming? 2000 years is a long time. We can speciate flys, though I'm not sure what the timeline is. Without any human studies of strict eugenics, what is the basis for possible/impossible on this timescale?
, much less a wide variety at once that all need to appear in the same organism and may even be mutually exclusive.
They also might just as easily be all selected for at once. Most of what you mention below are phenotypes that seem to run together. Sure maybe not, but either way its just an assumption that's plucked from the ether.
There's very few genes that actually follow Mendelian inheritance patterns. So far we've seen denser bones, stronger muscles, faster reflexes, keener eyesight, near perfect recall, enhanced hearing, enhanced smell, enhanced kinesthetic sense and proprioception, increased ability to analyze faces (something incredibly difficult already that utilize a ton of human wetware), extremely exaggerated primary and secondary sexual characteristics exclusive to the female sex (at least some of which completely reverse the human female trend to neoteny) increased fertility and the massive internal changes needed to support it, and an entirely novel (though cultivated in part by training) mode of cognition.
I noticed you forgot to mention increased occurrence of the ability to see the Onta. How are you factoring in that trait, which we know must be heritable based on the Inchoroi ability to graft it into their genome.
How about nonman DNA in the genome? We know humans are neanderthal DNA, so such a thing is not unprecedented, and in fact likely vital to the survival of our species.
It's too much for me to believe in a mere two thousand years with an extremely small and likely homogeneous starting population.
Its actually extraordinarily unlikely that they started with a homogenous population, otherwise inbreeding would have stamped them out long ago. They must have been very genetically diverse to begin with to have any chance at all.
We do all kinds of crazy stuff by subjecting test animals to extreme environments. We've been able to speciate fruit flys by splitting a group and putting one in a hot environment and the other in cold. We've seen bacteria assimilate cyanide into their genome when forced with no alternative.
We have ethics, so we haven't any experiments to show how extreme eugenics might affect a base population of more complex creatures, but by extension, people could accomplish in their own population similar results over longer periods of time. So a few decades to speciate flys, who not two millennia to nearly speciate humans?
denser bones, stronger muscles, faster reflexes
These don't have to be genotype changes.
You get denser bones by hitting hard stuff all the time. See - martial arts.
Stronger muscles and reflexes are the same - simply training.
Don't you think if you took an extraordinary athlete from today, and threw him into the first olympic games, that people would perceive him as a god?
Michael Phelps makes Mark Spitz look like a JV player.
Usain Bolt would make Jesse Owens look like he was standing still. (their best times are over 1 second apart in a race that lasts ~10 seconds. That's 10%, or 10 meters.)
Are the achievements of the Dunyain any more miraculous?
keener eyesight, enhanced hearing, enhanced smell, enhanced kinesthetic sense
These are hard to explain. I think you need eugenics for this. But how many generation? Is there anyway to estimate that?
Still though, phenotypic changes. Throw a kid into a dark labyrinth, his eyesight will underdeveloped and and his other senses hyper-develop.
faster reflexes ... proprioception... near perfect recall ... an entirely novel (though cultivated in part by training) mode of cognition.
These are all kind of the same thing. Increased cognitive ability would lead the the perceived quicking of reflexes, proprioception, and perfect recall. Yes, the dunyain's cognitive abilities are beyond what we have seen in humans. One might even say fantasy-esque.
Subjecting children to the kinds of extreme rigours that the dunyain do would likely lead to many of their traits as adults, including cognition. You can throw out genetics almost entirely for most of what we see. Adding in eugenics only heightens the odds that there is going to be some huge disparities between what is IRL and what we seen in the Dunyain.
So the big question: If it's possible, or conceivable in the very least, for parts of what are happening to the Dunyain to happen IRL, at what point do you factor in the idea that it just isn't Earth? Clearly the Dunyain are a fantastical breed of superhuman mutants in a fantasy world that don't exist IRL, but this isn't real life.
Why, if this or that combination of dunyain traits are possible, can't the rest be infused with a bit of fantasy? Why doesn't magic and subjective reality, alien non-human interbreeding and space farring alien, gods and demons, simply bridge that gap between "some of this can happen in real life" and "wow this is just too much to be real on Earth"?
Where to draw the line is arbitrary
But how and why did you draw it where you did, and why not choose to draw it somewhere else if it is in fact arbitrary?
Why not arbitrarily pick a line that leads to further enjoyment of the book?
Sure, you could pick to draw that line at magic and aliens and just throw the book in the fire, but you didn't. I'm asking about the
why rather than the fact itself.