We’re being explained about chromosomes and gametes and shit, and the recent video we watched mention Chromosomes cross-exchange in the gametes in the first or second cycle. The idea I understood was “genes are swapped between them, so they won’t end up really anything like the parents” which confused me more because that is pretty much how genetics work. I am like my mother physically, and my dad in the metabolistic and internal systems. So I asked my science teacher if the cross-exchange was why eugenics is seen as illegitimate, and she said something along the lines of “no, eugenics is about making a pure race, but often there is more genetic variation intra-race than inter-race.”
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I don’t understand this? Does she think race is a continental thing? Because a northern euro is far different than a south Euro in genetics, to the point I would call different races entirely. And there is far more difference between race in the phenotype viewpoint.
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tl;dr learning about chromosomes, mitosis and meiosis, and sexual reproduction, and I am confused about the cross-exchange and what my science teacher is saying. What is the scientific flaw about eugenics? Not its practical flaw in which I could name many, what is it’s scientific flaw?
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Chromosomal cross-over doesn’t mean that you won’t be anything like your parents.
Let’s say we’re talking about chromosome number 7. You get one copy of this chromosome from each of your parents. Let’s talk about the copy you got from your mom (although it’s the same for your dad). She herself has two copies of chromosome 7 – one from *her* dad and one from *her* mom (your grandfather and grandmother).
Without chromosomal crossover, your mom would have passed on to you either her dad’s or her mom’s copy of chromosome 7. So from your mom’s side, you would *either* have gotten your grandfather’s *or* your grandmother’s chromosome 7.
But that’s not what happens. Instead, in meiosis, the chromosomes cross over. That is, your grandpa’s and grandma’s strands of chromosome 7 kind of braided together and where they crossed, everything on one side became one new strand of chromosome 7 and everything on the other side became another strand. As though you took two copies of the same book, ripped out the pages, and then made two new books out of the pages, with each book containing all the pages in the correct order but taken from the two original books at random (e.g. if the two books were printed one on red paper and the other on blue, the new books would have red and blue pages randomly interspersed). Your mom then passed one of these new, recombined chromosome-7 copies on to you, meaning you got genes from both grandma *and* grandpa on your chromosome 7.
As for your question about race, you are making assumptions based purely on appearance. You don’t actually know anything about the underlying genetic variability. The point is that the genetic variability between individuals is far greater than the differences you see between (putative) “races”. That is, if Alice and Bob both hail from Northern Europe, and Charlotte hails from sub-Saharan Africa, then Alice and Bob will be about as different to each other as they are to Charlotte (on average, if you picked Alice, Bob and Charlotte at random).
For this reason, the idea of racial “purity” is unscientific, and so it makes no sense to use eugenics to enhance or maintain this supposed “purity”. However, racial purity and eugenics are not one and the same thing. Eugenics basically just means you control which individuals get to procreate, in order to promote certain traits or suppress others. Scientifically, this is sound. It’s just incredibly unethical. But in principle, you could totally do selective “breeding” in humans and achieve certain effects. E.g. if you only allow tall people to procreate (say, only the tallest 10% of individuals) then every new generation will be taller than the ones before. But of course, not allowing shorter people to have children is incredibly cruel and immoral.
Even more subtle methods are still unethical. E.g. you could just give financial incentives to tall people who have children (rather than e.g. forcibly sterilizing short people or inseminating tall people), but that’s fundamentally still the same thing – just dialed down a bit. You’re still making it (relatively) harder for short people to have children. Also, when you try to breed certain traits out of the population, you’re effectively performing a kind of slow genocide.
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