Neither was the main focus of his paper. Still, it's always interesting to see what brings the two together (since they're in different language families).
The point of impact this time?
...language is a very strong determinant of ethnic identity, but it is not the sole determinant and sometimes it has very little to do with ethnic at all.
Writing immediately again in the next sentence, he stresses:
I would ask you to keep one thing in mind: language and culture and race are three totally independent quantities in principle.
What does he mean by this?