Kim Wook et al. (2000) said that, genetically, Vietnamese people more probably clustered with East Asians of which the study analyzed DNA samples of Chinese, Japanese, Koreans and Mongolians rather than with Southeast Asians of which the study analyzed DNA samples of Indonesians, Filipinos, Thais and Vietnamese. The study said that Vietnamese people were the only population in the study's phylogenetic analysis that did not reflect a sizable genetic difference between East Asian and Southeast Asian populations. The study said that the likely reason for Vietnamese people more probably clustering with East Asians was genetic drift and distinct founder populations. The study said that the alternative reason for Vietnamese people more probably clustering with East Asians is a recent range expansion from South China. The study mentioned that the majority of its Vietnamese DNA samples were from Hanoi which is the closest region to South China.