Proto-Mongoloid refers to early representatives of the Mongoloid phenotype. Notable examples of fossils exhibiting proto-Mongoloid phenotypes are found in Late Pleistocene (Upper Paleolithic) fossils, notably the Minatogawa skeletons and the Liujiang crania. The modern Mongoloid (East Asian) phenotype develops fully only in the Neolithic (after 10 kya).
The term Southern Mongoloid is used to refer to the indigenous populations of Maritime Southeast Asia. They have often been assumed as deriving an early admixture of Mongoloid and Australoid types. Based on the morphological criteria of Sinodonty and Sundadonty for the dental morphology of northeast and southeast Asians, respectively, it is now thought more likely that Sundadonty is the ancestral type, inherited by Proto-Mongoloids from their Proto-Australoid ancestry, and Sinodonty is a morphological innovation limited to modern northeastern Asian Mongoloids.
Ainu people, belonging to Proto-Mongoloid, was considered to be Caucasoid at one time, because of their different characters from Yamato people such as finely chiseled features and thickly haired. However, these characters may be symplesiomorphies (shared retention of traits of the most recent common ancestor) rather than synapomorphies (shared derived traits). Recent genetic researches have revealed that the closest relatives of Proto-Mongoloids are Neo-Mongoloids, and their ancestors split tens of thousand years ago.
"Neo-Mongoloid" (modern Mongoloid) migration to Japan is associated with the Yayoi people (8th-3rd centuries BC). The Yayoi interbreeding with the indigenous populations formed the stock of the modern Japanese people. 
- Matt Cartmill, Fred H. Smith, The Human Lineage, John Wiley & Sons (2009), p. 449.
- Keat Gin Ooi (ed.), Southeast Asia: A Historical Encyclopedia vol. 1 [Angkor Wat to East Timor], ABC-CLIO (2004), p. 495: "many of the present Southern Mongoloid populations of Indonesia and Malaysia also have a high degree of Australo-Melanesian genetic heritage" citing Bellwood (1997:89,92). See also: Fredrik Barth, "The Southern Mongoloid Migration", Man Vol. 52 (Jan., 1952), pp. 5-8. .
- Hamada, Ryuta, Kondo, Shintaro & Wakatsuki, Eizo. (1997). Odontometrical Analysis of Filipino Dentition. The Journal of Showa University Dental Society, 17, p. 197, citing C.G. Turner, "Teeth and prehistory in Asia", Scientific American 260 (1989), 70-77.
- "The present Southern Mongoloids are thought to have retained a Sundadont dentition from this ancestral Proto-Mongoloid population and hence to have developed in situ within Sundaland and adjacent parts of Mainland Southeast Asia. Polynesian and Micronesian dentitions are also within the Sundadont range, thus attesting to their Island Southeast Asian and Proto-Mongoloid origins. The 'Sinodont' teeth of northeastern Asia and the Americas are also thought to have evolved from an original and more widespread Sundadont-like ancestral form." Peter Bellwood, Prehistory of the Indo-Malaysian Archipelago: Revised Edition (2007), p. 90.
- figure based on W. W. Howells, Getting here: the story of human evolution (1993), p. 206 (figure "The Distribution of Asian Peoples").
- Studies on the affinities of Sakhalin Ainu based on dental characters: The basic populations in East Asia, III T Hanihara - Journal of the anthropological society of Nippon, 1990