There is only one Caucasian.
Johann Friedrich Blumenbach, the “father of craniology”, “coined the word Caucasian to describe the white race. It is curious that this word– which is still widely used– is based upon a single skull in Blumenbach’s collection which came from the Caucasian mountain region of Russia. Blumenbach found strong resemblances between this skull and the crania of Germans. Therefore, he conjectured that possibly the Caucasus regions may have been the original home of the Europeans.”
~ Thomas F. Gossett, Race: The History of an Idea in America, p. 37-8
The Raceless Gospel 
This topic is also covered well in the book “The History of White People” by Nell Irvin Painter
I have a signed copy on my bookshelf. It’s on my long list of books to read. Thanks again and again, Glenn.