I agree about "erbal" and the "h" being silent, but I don't think "human" or "humanity" have a pure "y" sound instead of the "h". The soft "h" coming out as more of a "hyu" sound, but still significantly different to me than "yu". A different part of the back of the mouth is stressed to pronounce the two sounds. It's a subtle difference, but definitely not a "y". My tongue, mouth and throat understand the difference between a soft "h" and a hard "y". :P

Do the first syllables of "human" and "you" sound the same to you when Americans say it? That's interesting.