Wow a sign language question. woo hoo ;-)
First of all I should say that I am a ASL interpreter. So not just a hobby for me, but career. There have been a few things said that I would like to clear up and comment on.
First the question at hand (since usually I’m off topic)
Sign Languages don’t only differ country by country, but in some countries region by region. Also keep in mind that they are natural languages, not created languages. How they have evolved and spread also has no relation to the spoken language. As an example, ASL (USA, Canada, Guam, Puerto Rico) is related to Old French Sign Language. Modern French Sign Language and ASL actually share something like 60% of their vocabulary. However BSL (England) and ASL are mutually unintelligible. A Deaf person from England and a Deaf person from America would be better off texting to each other.
Also keep in mind that Signed Languages have their own syntax independent of the spoken language of what ever country they are in. ASL shares more grammatically with Mandarin Chinese than it does with English.
@Follaholic
As for finger spelling (ie. Hand shapes that represent a letter of some alphabet, or syllable of a syllabary) that is actually less a part of a signed languages than one may think. Although they are an important part, they are only used to borrow words from a spoken language. So they come into play when you need to specify a word that may have no equivalent in a signed language. For example someone’s name. So the point is, knowing a finger spelled alphabet helps less than one might think. (There are however times when the borrowing becomes an official “loan word” in which case it is modified to be incorporated into the language more naturally)
@gailcalled
I have been keeping up The Amazing Race too. Unfortunately, for a fluent signer of the language, it can actually be heart breaking to see how badly his mother interprets for him, and how badly she signs to him. Or even worse when she choses not to sign to him at all. This however is usually the case for most Deaf people with hearing parents. Rarely do the parents ever learn the Language fluently, and the gaps are left for the Deaf person to do the work to fill.
@asmonet
I really don’t want to burst your bubble. But Deaf people usually have something to say about people who find ASL “fun” to use, and see Deaf people as an opportunity to practice their signs with. Often times better communication would be had writing on a pad of paper or texting back and forth. As an interpreter I’ve had to correct many a mistake made by the nurse who “knew a little sign”, or the coworker who “took a sign language class”.
Ok sorry for anyone who actually read the whole post. I got carried away ;-)