A friend of mine, who's Caucasian, was living in Japan and had to go to the hospital once. The doctor asked him what the normal body temperature was for a white person. The doctor didn't really believe him when he said it's the same as the Japanese.
Before drugs developed outside Japan are approved for use in Japan, as part of the approval process they will test the drugs on Japanese using "foreigners" as a control. And it doesn't really matter where the foreigner is from, either. Like you could have a drug developed in Germany and they'll happily grab a random Aussie for the trial. Years ago I knew a guy who made extra money every few months doing this.
That's because it's not the same. When my japanese wife has the same body temperature as mine, she has a (slight) fever.
Edit: Conversely, my body temperature when I have a slight fever would be considered serious.
Take it with a grain of salt because this is from a pharmaceutical group, but this page claims the average body temperature of the Japanese was 36.89°C 50 years ago and that it was 36.20°C as of 2009.
http://www.sawai.co.jp/kenko-suishinka/illness/200909-02.htm...
Edit: although, that might as well be due to the aging population. That said, I have been told that my average (by France standards) temperature was "a little high".
I wonder if there's a diet component. When I lived in Japan, after a while my temperature was an average 0.3 degrees lower than it used to be before. It returned back to what it used to be before after leaving Japan and switching to a different diet
