KOREAN ROOTS OF THE JAPANESE PEOPLE
Marmot's Hole has a link to an old article by Jared Diamond (if you haven't read "Guns, Germs and Steel," try to when you have time. great book and winner of the Pulitzer) which analyzes various theories on the origins of the Japanese. Informative and some decent comment's by Marmot's readers. Here's a excerpt from Diamond's article:
One theory is that Jomon hunter-gatherers themselves gradually evolved into the modern Japanese. Because they had already been living a settled existence in villages for thousands of years, they may have been preadapted to accepting agriculture. At the Yayoi transition, perhaps nothing more happened than that jomon society received cold-resistant rice seeds and information about paddy irrigation from Korea, enabling it to produce more food and increase its numbers. This theory appeals to many modem Japanese because it minimizes the unwelcome contribution of Korean genes to the Japanese gene pool while portraying the Japanese people as uniquely Japanese for at least the past 12,000 years.
A second theory, unappealing to those Japanese who prefer the first theory, argues instead that the Yayoi transition represents a massive influx of immigrants from Korea, carrying Korean farming practices, culture, and genes. Kyushu would have seemed a paradise to Korean rice farmers, because it is warmer and swampier than Korea and hence a better place to grow rice. According to one estimate, Yayoi Japan received several million immigrants from Korea, utterly overwhelming the genetic contribution of Jomon people (thought to have numbered around 75,000 just before the Yayoi transition). If so, modern Japanese are descendants of Korean immigrants who developed a modified culture of their own over the last 2,000 years.
The last theory accepts the evidence for immigration from Korea but denies that it was massive. Instead, highly productive agriculture may have enabled a modest number of immigrant rice farmers to reproduce much faster than Jomon hunter-gatherers and eventually to outnumber them. Like the second theory, this theory considers modem Japanese to be slightly modified Koreans but dispenses with the need for large-scale immigration. (full article)