There is a big subplot about “racism” in the wizarding world and wizards that have a human parent called mudbloods and pure blood wizards.
Is this just awkward phrasing or was there at some point in the past a wizard race or wizard species? Or are we to assume its just nonsense that is widely believed in wizard society?(there is no wizard race, magic ability is just random).
No, no isolated wizarding “race” or species. Apparently Muggles have always produced a few witches and wizards while magical families have always produced a few Squibs (wizard-born Muggles).
At least, we know that even as early as the founding of Hogwarts a thousand years ago or more, the magical community knew that some witches and wizards could be Muggle-born. However, apparently intermarriage between magicals and Muggles is commoner now than it used to be.
So magical ability appears to be a genetic trait that’s caused by a fairly common mutation, but isn’t totally heritable.
(Actual geneticists feel free to correct or modify this explanation.)
Actually if you view it as a genetic trait you’d also have to regard it as a remarkably common mutation (or maybe an extremely recessive gene). It’s unusual in genetics to have a trait (like magical ability) that quite often pops up in children of parents who not only don’t have the trait but have no known ancestors who do.
I don’t think magic does pop up often in muggle families. In the HP series, we only *hear *about the ones that do.
If the wizard gene appears in about 1 out of 1000 people, then you’ll see it in about 1 in 1 million muggle children. You’ll see it in virtually all wizard-wizard children.
But there are a lot more muggles than wizards, so the ratio of mudbloods to pure wizards is pretty high.
All this makes me think of white bison, where one only shows up every fifty years or so.
I’m pretty sure that J.K.Rowling has said that “mudbloods” had to have had some recessive magical genes from way back. Basically, no couple who are pure-muggle since Cro-Magnon days could ever beget a witch or wizard.
Rowling has said that squibs are very very very rare, and that muggle-born wizards and witches are more common. This would mean that magic is passed on by recessive genes.
However, esp. given the persecution in the past, it’s quite possible for magical children to be born into “muggle” families who really have wizards back in the family tree (3 or 4 generations prior) who stayed hidden. After all, in all of Great Britain, there’s only one all-magical village; so obviously the rest live among the muggles, making intermarriage possible.
We know from the real world that most traits don’t follow the simple dominant-recessive one-allele pattern of Mendels peas, but rather, are co-dominant and multiple-allele. This means that the standard Mendel square doesn’t apply. We have real life examples with skin colours, which has 6 alleles from pure white to dark black, and where despite the stigma against intermarriage and the relativly short time of interaction between black and white due to lack of transport previously, still occasionally odd-coloured children pop up due to recessive traits - e.g. a white couple having a darkish baby because one grandparent was mixed. Or blacks being light-skinned enough to pass.
In one interview Rowling said she based the view inside the Magic community on the Nazis race laws where “being Jewish” went back three generations (which is less severe than the one-drop rule), so she wasn’t thinking biologically, but sociologically and culturally.
wanders off, muttering and grumbling about “why is it, therefore, that they don’t get modern muggle society?”
wanders back
It’s also worth considering that the only sign that Harry was an untrained wizard was that a few odd things happened around him and he had a little chat with a snake. Harry is (destined to be) a great and powerful wizard and that’s it? (ignoring the magical protections on the house that might have dumbed-down his power levels for him so as to avoid notice from HWMNBN); it’s not outside the bounds of reason that many potential wizards might never realize it and live entire wizard-free lives.
This would, for example, explain crazy cat ladies who think they can talk to their cats, and children with overactive imaginations.
Well teenagers and parents live under the same roof, but do parents really get teen culture? 
A few individuals falling in love because you see a nice woman/men at the village dance is a far cry from getting the culture when you live in a weird house outside the main village and have enough interaction among your brood of children like the Weasleys have.
Well he was untrained and didn’t have a wand. Kids need to learn a lot of non-magical skills, too, whether it’s writing or sports.
Mutants and heroes always need a training montage to master their new power, too. The Eragon method, where the hero just has the skill for something without explanation is not a good alternative, because to most readers it breaks suspension of disbelief. Learning hard to master a skill, even if it’S magic or controlling mutant powers, is something people can relate to. Pulling a skill ready-made from your ass is a cheat.
I can’t remember anything canon about that. Until Goblet of Fire, Voldemort wasn’t even in England, let alone in a form where finding Harry was a problem. And the ministry kept kind of a tab on him anyway because he was underage and thus not allowed to do magic outside school. And in Deathly Hallows we learn how Dumbledore’s special protection worked - deep magic without spells.
Random bursts of magic acting unpredictably are not easy to study with a rational mind and learn how to control. And Harry is not the strongest bestest wizard (he’s only a teen, remember) in history or in England, but has stronger-than-average magic power, plus studying hard (for the Triwizard tournament for example and other instances where he learns obscure spells that come in handy later) and some non-magic skills (his seeker ability).
It’s quite easy to imagine many children with weaker magic never experiencing raw magic. Remember how in Philosophers stone, Neville tells how his family was afraid he was non-magic because he never showed any signs, until his uncle held him out of the window and accidentally dropped him? Now, if you didn’t suspect magic, you wouldn’t test your kids that way! (And if it happened, you would brush it off as Miracle of the Virgin or similar, glad that the kid was unhurt).
My hypothesis has always been, at least for British magicals, that they withdrew from mingling with the Muggle community around the sixteenth and seventeenth centuries when witchcraft trials became popular. Yeah, we know from the canon that actual witches and wizards were seldom killed or injured by Muggle punishments, but the whole phenomenon can’t have been very pleasant for community relations.
And British witches and wizards never fully re-integrated into Muggle-majority society, so that’s why they’re technologically more or less still in the early modern period: they have torches, candles, mirrors, coinage, quill pens, etc., but fewer items of recent technology. (Barring some major Industrial-Revolution inventions like newspapers, steam trains and flush toilets, probably more for the author’s convenience than anything else.) And of course, don’t forget that electricity and electronic devices can be messed up by strong magical forces, so the incentive to join the present-day high-tech society is significantly diminished.
Cultural and historical factors play a role, too. By this time, the British magical community is sentimentally attached to the traditional household and technical accoutrements that have been a distinctive part of their lifestyle since the Great Withdrawal (that’s my name for the witchtrial-era split between Muggle and magical communities ;)). They like their quills and parchment rolls and gold coins and all the other trappings of “proper British witchcraft and wizardry”, and they have little interest in modernizing.
I think Ethilrist is saying “Why not have those Muggle-borns being the ones studying Muggle tech?” instead of having Mr. Weasley trying to figure out what a rubber duck is for.
Arthur Weasley’s job is just a stupid weak source for easy jokes. Thinking about it ruins everything. Says ‘fellytone’ when he means ‘telephone’? Just dumb. Laugh, or don’t, and move on.
We don’t know how many muggle-borns were in Hogwarts previously, and how they reacted to the wonder of the Wizarding World when learning about it age 11. Many may have embraced the Wizard world for being cooler and forgotten about their Muggle roots.
At age 11, most technology is magic to muggle kids, too- they don’t really know how a telephon works (today an iphone doesn’t have a string, so analogies to string-can-phones won’t work. How many adults know how a TV really works, aside from “You turn on the button and pictures appear?”. Since this is Great Britain, they won’t be familiar with guns, either.
You can see it best with Hermione taking Muggle studies for a different perspective (a very good idea), but nobody else being interested enough, and when Ron mentions that Mr. Weasly’s obsession with and fondness for Muggles has held him back at the Ministry. Since the wizarding population is so small - under 10 000 in Great Britain, apparently - they need a smaller ministry; at the same time, wizards live much longer. So the guys now in power are 50 or 70 or 100 years old- even if they did come from Muggle families, there wouldn’t have been much in Muggle tech to interest them.
Remember that everything that works with electricity doesn’t work in a magical field, as Hermione explains during GoF when they wonder if Rita Skeeter has bugged the place. So a lot of the cool tech - computers, TV, playstations, ipods - won’t work. And they have had moving pictures before the Muggles had, they had flying things before the muggles had airplanes, they had death spells before the muggles had reliable guns (and don’t jam or run out of bullets), they had instant transportation which Muggles still don’t have, and a cool purple steam train instead of boring modern ones - so what incentive is there that looks sufficiently cool for a wizard to spend time on?
After all, the years spent studying muggles (which most wizards regard as weak or inferior to them) could be spent studying spells much more effectivly or inventing new potions, etc.
Hermione uses some Muggle tech - but during Deathly Hallows, she doesn’t think of buying MREs and a camping stove in a supermarket, but tries magic and what they find (they are staying away from big cities, too, though).
Compare the scene in PS, when they fall down onto the devil’s snare, and Hermione thinks of how to make a fire “If only I had matches” and it takes Ron to point out that she’s a witch, she can magic a fire. That’s her old muggle thinking. But in later books, she thinks of magic first because it’s so much more convenient. Only once the war starts and muggle methods would offer secrecy does she think of this again - but trying to teach other wizards who have done things a certain way for decades new methods is not going to be quick or easy.
How many muggle people older than 60 today have trouble adapting to new technology that wasn’t around when they were young? The majority, I’d say, so it’s not unrealistic.
I always wonder if the reverse holds. If you set up a powerful electric or magnetic field in an area, does it prevent magic from working? Can a Tesla coil block spell use? Sadly, the books never delve into the interaction between magic and technology in any detail.
Back when I started reading that series, I had a theory, based mainly on the described physical characteristics of some of the wizards (Snape, Hagrid, Flitwick), that at least some wizard talent (genes) came from non-human magical creatures mating with humans.
Later on in the series, it came out that Hagrid had a giant ancestor, and that pretty girl (forgotten her name) had a veela ancestor, so I figured I’d got it right.
Flitwick’s would have been some sort of elf thingy, and Snape’s one of those swamp critters that lures people off paths 
Which makes the whole “pureblood” thing a little ironic…
Isn’t it in the canon that Flitwick has goblin ancestry? (google google) Yes. And the quarter-veela French girl ended up being sister-in-law Fleur Delacour.
Snape, though, seems to be pretty definitively human: Muggle father, witch mother.
Rowling couldn’t be bothered to get herself a perpetual calendar and use it, and you want her dabbling in electrical engineering? 
Many folks are familiar with Clarke’s Law, that any sufficiently-advanced technology is indistinguishable from magic. What they don’t realize is that, from the point of view of most people, our technology is already sufficiently-advanced, and has been for ages. It’s not just 11-year-olds: Most adults hold a magical view of the technology they use, too.
Which was of course one of Rowlings points - most clearly in the OP book when the Minister of Magic talks with the Muggle prime Minister about the deaths from the Deatheaters, and PM says “But you guys can do magic!” and the Minister says “So can the bad guys”. Or in the “Beedle the Bard” tales - dead people can’t be brought back again, and magic can’t solve the real problems of love and loss and rejection and …
Rowling said or wrote somewhere that she intended the magic as analogy for today’s technology, which can be used both ways, good and bad, and which most people don’t understand, which can be dangerous if they let others use it without making rules about proper usage. But that point often gets overlooked in all the action or minor inconsistencies like moon phases.
Well the great Sir Arthur Conan Doyle writing about the Great detective Sherlock Holmes also couldn’t be bothered about moon phases …
Obviously she shares the attitude that the story telling comes first, details second. And she studied languages, not physics. Hers is a fantasy world, not SF, so she’s not obliged to write out technical rules on how things would work. And since we see only a slice of the whole world through the eyes of a kid and teen, she doesn’t have to - a muggle kid of 11-17 writing about our world wouldn’t tell us all the details about how the economic crash worked or why TVs switch over to digital signal or all the other knowledge of the world. Sometimes, he would get stuff wrong, and a lot of stuff would never enter his view.