Originally Posted by sraL
lmao i'm agreeing with you bruh
One thing you're severely overlooking in your maniacal strides toward human perfection though is a little thing called "Regression to the mean"
You would have to pick the ones that conformed to your wishes and ONLY breed those.
Regression to the mean applies to a single generation in a "randomised" population and to complex traits. If, in a population with mostly brown eyed people, you bred two with blue eyes, all the kids would have blue eyes. And if vice versa you'd still have 75 % offspring with brown. No regression towards the mean. (If we pretend there are only blue and brown eyes and ignore all the genes we don't mention in high school biology.)
If you pick only those with 160 IQ to breed, the first generation will only have a small number of the super-intelligent, but they will have more super-intelligent than the population as a whole, and more of the highly intelligent, and intelligent, and more of the "average". Pick only the best from this new population and the third generation will be even "better".
Of course, for this to be successful, we have to prevent those not selected from breeding. Unless all you want to do is create a sub-group of humanity with unusual traits, it doesn't matter to you that the rejects are breeding somewhere outside your empire of intelligence/beauty/sports ability.
Probably the most famous study of selective breeding for mammalian behavior is the domestication of the silver fox.
About 5% of males and 20% of females were allowed to breed.
The regression to the mean refers to the mean of the breeding population. If a new splinter population is created through selective breeding, reproductive isolation, runaway sexual selection, etc. then a new mean will be created (e.g. founder effect).
As an aside, and I don't know if this still has much pull in modern thinking, but one idea is that humans basically self-domesticated. This partially explains human neoteny and the increased willingness to cooperate with others, lessened aggressiveness compared to primate ancestors, etc.
One can only guess at what selective breeding could do for modern humans. There are physical limits. To the great consternation of mothers, we're about maxed out for skull size vs. birth canal circumference. People who are 7-8 feet tall have a lot of problems with their feet, knees, hearts, etc. It's interesting to wonder if you could breed passive cow-like humans (with us being the auroch). A big hit for futuristic totalitarian dystopias, I'm sure.
Selective breeding really does not depend on new genes coming into existence.
I think the focus on a trait like intelligence is maybe making the discussion more complicated than it needs to be, because we don't even know the extent to which genetics controls intelligence.
Go back to basic genetics. A gene codes for something like a protein product that produces a result in the final organism (the phenotype). Genes in a population exist in multiple versions - alleles. The paired nature of DNA means that an individual actually has two genes in most locations and it's possible to have two different alleles in the same individual.
But selective breeding looks at a whole population. There are many different alleles in the population - it could be dozens or hundreds. A natural population has a certain ratio of those alleles that mix around and generally reach some equilibrium. If you want allele #23 in your in your final breed, you can find two individuals in the population who have that and breed them. At least some of their offspring end up with 23. Eventually, you can get them to "breed true" where their DNA contains only allele 23 and nothing else.
For a single gene, you could accomplish this in a single generation. Two parents that are 23-? and 23-? will produce 1/4 of their offspring that are 23-23. If you can tell those apart, then you're done. Sometimes 23-? and 23-23 look identical (have the same phenotype) and that complicates things, because it means 1/4 of the offspring will be ?-?. That's one reason why establishing a stable breed is more difficult in real life than a single generation.
Of course, doing anything complicated also involves multiple genes. You don't go from a Chihuahua to a Great Dane with a single gene. The more genes you need to combine, the more generations you need until all the random combinations come out the way you want. Eventually, you reach your own equilibrium of alleles based on artificial selection rather than the equilibrium from nature that came from natural selection.
As far as returning to the median goes... most of the time, you haven't completely eliminate all of the old genes. Plus, the old genes can be put back into a population by breeding with wild species. Once you stop artificially selecting, then natural selection takes over again and you tend to wind up with the same equilibrium that the wild species had originally.
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