I guess my question would be:
If the languages 'evolved' to stay within a tight little group, then why haven't those humans got physical characteristics that differ markedly from their 'remote' relatives?
Indo-European languages "evolved" from a common ancestor, which linguists call Indo-European.
then why haven't those humans got physical characteristics that differ markedly from their 'remote' relatives?
Different groups of humans look different, of course. Be that as it may, comparing language development to human evolution is kind of silly.