Jews: Why the animosity towards them?

[Ramses II CP]

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A person's "race" (in common usage) can usually be identified by skin colour, facial carticture, feature size, hieght, possibly hair colour, etc. Things like that are often genetically tied to certain "races" and that has been proven by genetics. It is an "invention" of the 20/21st century, but that does not mean it is not true.
Again, there is nothing wrong with observing differences. (Like when a blonde school girl notices that there are other girls with blonde hair and some with brunette)
What is wrong is when you use this difference to justify your hate. (Like if all the blonde school girls were to stick together and tell the brunette girl that she couldn't hang with them because of her hair colour)
People use differences (of any kind) to excuse their barbaric behavior (which they have to do to themselves before they even commit their barbaric act).
It is true that if there were no differences there would be no conflict, there would only be one person. :P
Just because people target differences to excuse their hate does not mean that differences are bad. That is like saying that to prevent people from shooting us in the head we should all be decapitated. :P (I really love these 2-bit analogies :P)
Your head is not bad, the person's act of shooting it is. Likewise differences are not bad (and it is the heart of racism to say that they are), but using them to excuse wrong doing is bad.
There is nothing wrong of people being proud of their differences. The blonde and brunette can both be proud of their hair and be just as beautiful. Being proud of who you are doesn't mean that you think people with diferences are inferior.
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The problem with what you're suggesting is right there at the top, 'in common useage.' If you check the dictionary definition of 'race' you'll find that it is such a mishmash of presumptions and contradictory statements as to make the word useless. Here is dictionary.com's version:

http://dictionary.reference.com/browse/race

For convenience, here are some of the choices:

a group of persons related by common descent or heredity.

any people united by common history, language, cultural traits, etc.

any group, class, or kind, esp. of persons

So while you claim that genetic differentiation has been tied to different 'races' that is not a proven fact. It's more correct to say that genetic traits run according to heredity, so that tracing a group of people to a common ancestor can mean that they share traits. However tracing them a little further will broaden the pool of traits, while tracing them a little less far will narrow it. There is no meaningful way to say 'Trace this far, and no further, to determine X race.' As I pointed out, in an eyeblink of evolutionary time every living human can be traced to a single ancestor. There are no true racial differences, only familial differences.

I agree that there's nothing wrong with observing and noting the gross biological differences between groups of people, but when you start to class people according to those incredibly shallow and misleading differences you fall into the trap of racism.

Consider that in order to draw the lines around an imaginary 'race' of Jews you have to decide how much interbreeding is allowed and for how many generations, and all that after picking exactly how many generations deep into the past you're willing to reach. The task of merely defining such a 'race' grows exponentially every time someone marries into or out of a supposedly Jewish line. Setting aside Judaism for a time, consider the Maori, who lived in near genetic isolation for an indeterminate but quite significant period of time. Currently there are, as far as can be determined, no 'full blooded' Maori left in the world, and that's just two hundred years after their genetic isolation ended and large scale colonization began. Trying to isolate a 'race' of Jews when the self-identified Jewish people have thousands of years of intermarriage and frequent scatterings across the face of the earth is madness.

For my part, I think there are two useful distinctions of ancestry, your immediate family, the three to four previous generations whose genes have a direct impact on your health and development, and your species. All that guesswork about this hundred generations are the Jews, but not back to a hundred and twenty, because then we'd just be Arabs and Africans... is silly and divisive. We're the human race. We have so much more in common than apart that the differences are entirely mutable.