So what are the physical characteristics that distinguish Okinawans from Japanese? As with any case of discrimination, there are usually characteristics that are emphasized by the majority group to identify the minority.
The usual list of characteristics are that Okinawans are:
That said, I believe that you can see a difference between the elder Okinawans in Hawaii and the younger generation. The elder generation, particularly the ones who came from Okinawa or where born to that generation here, did tend to be shorter than we see today. This was almost certainly due to the diet of the Okinawans in Okinawa and here in Hawaii at that time. A poor diet usually results in lower growth rates. (Remember that before the war, Okinawa was the poorest prefecture in Japan.)
I went to a meeting for people from Itoman. One of my friends was in the group. Three people who were raised in Okinawa before the war shared their experiences. They all said that just about the only thing they ate in Okinawa was purple potato. Rice was a luxury item. Even finding wood for a fire took a lot of work.
Okinawans have the greatest longevity in the world, probably because of their meager diet (by American standards).
At that meeting, one gentleman shared how he came to Hawaii and worked as a dishwasher. He had to walk a long way to work, then work long hours. It was a hard job. But he said that even the lowest paid worker in Hawaii could still afford to eat a hot dog and musubi (rice ball). Even the poorest worker here was better off than he would have been in Okinawa.
So diet may have made Okinawans shorter, certainly by American standards.
But I believe that the physical differences emphasized in the prewar years were exaggerated. This always seems to be the case when prejudice is involved.
My point is that Okinawans and Japanese were not very different physically. The differences between them was more cultural (art, language, diet, clothing, hair styles, dance, religion, etc.).
And in any event, any physical differences (even if there were any) did not seem to affect the spread of Karate to mainland Japan and the world. The techniques of Karate work for all people -- not just Okinawans.
Charles C. Goodin