Quote:
Most scholars believe that people from the Asian continent came to the Japanese archipelago in two migrations. An early wave brought the Jomon culture--hunter-gatherers who made pottery--to Japan more than 10,000 years ago. A second migration began about 2,300 years ago, when the Yayoi people, entering from the Korean Peninsula, brought weaving, metalworking, and rice culture to Japan. First appearing on the southwestern island of Kyushu, by ca. A.D. 300 Yayoi culture had spread throughout most of Japan, altering all local cultures south of Hokkaido, the northernmost island. Michael F. Hammer and Satoshi Horai are examining the extent to which the Jomon did or did not contribute genetically to the modern Japanese. Current hypotheses can be classified as replacement, hybridization, or transformation. In the first, Yayoi immigrants replaced the Jomon people. Hybridization theories claim that modern Japanese are descended from both groups, in which case they should have genes deriving from both the Jomon and Yayoi people. Transformation theories posit that modern Japanese people gradually evolved from the Jomon. Hammer and Horai, based on their study of the Y chromosome, conclude that hybridization, a mixing of Jomon and Yayoi stocks, is the most likely explanation for the origin of modern Japanese.
looks like there's a couple theories on that, one which would not refute his point, if the jomon were replaced leaving no trace of the pre-alien human population, and the other, the jomon not being replaced and the mixing of the two people, would hurt his point because as far as i know i've never heard of people of japanese descent having a different dna structure.