At least three of the four ethnic groups a far from homogenous (genetically). Han Chinese is made out many people who adopted the basic Chinese culture starting in northeast China. The Japanese people's origins are still debated (traditionally, Shinto Japanese consider themselves all descended from the first emperor, and that they comprise the single, Yamada race. Most other scientists think that the Japanese have varied origins, with ancestors from the north, from Korea in the west, and even peoples from the south and Polynesia). And every American should know the heterogenity of Americans of European descent.
All humans are part of one race (and there are no subspecies) with very little genetic variation (the result of separation by at most some 5,000 years).
You are confusing terms here. Races are subgroups within a species that can be simply distinguished from one another by differences in outward appearance, differences in vocalization, and differences in behavior and response to stimuli.
The existence of seperate human races is simply demonstrated by variations in skin, eye, and hair color, facial type, and typical body size and proportions and more complexly demonstrated by differing reactions to medical care and risks of various diseases of, for example, people from sub-saharan Africa vs. people from east Asia vs. people from Europe.
The fact that there is very little genetic variation between human races does not mean that they are indistinguishable or undetectable. In fact, there are clear marker genes in our DNA which allow for a quick determination of the racial background of the person donating the sample. This is why those companies that ask you for a DNA sample and promise to tell you your genetic background can do what they do.
What do you think are the origins of the Ainu people? I have read a little about them. Some people think they have ancient European origins, some people don't think they came from Europe. Are the Ainu mixing with other Japanese or are they still pretty much isolated?
I thought the Australian aborigines had been isolated for something like 40,000 years.
-ccm
I'm sure you have a nice home page, but it doesn't appear correctly on my monitor: text over lapping and images scaled down from big ones that don't fully appear.