Not sure if this has been mentioned or not, but human settlement in India has been dated to >74 Ka by the Toba volcanic ash overlying stone tools. The Toba event made the subcontinent uninhabitable and isolated the Australasian survivors in southeast Asia from the rest of humanity.
The remnants of the decimated human population were confronted with a very sudden planetary cooling as a result of the Toba event, and the adaptive pressure has been hypothesized as the driving factor in the development of a cold-adapted east Asian branch from the Australasian trunk, enhanced by the importance of founder effects among the surviving remnants.
The Dravidian settlement was the re-occupation of the Bengal shore by Australasians. The tone language trait of east Asian/Australasian cultures (along with an isolated tone language group in the Indus Valley) is believed to reflect African-derived tone language among the original migrants.
Looking closely at the faces of Australasian-derived Indians, the similarities between Australasian and east Asian facial shapes are striking: round, with broad cheekbones and low facial topography. It’s looking more and more like certain northeast Asian facial features (Ainu brows and heavy Korean jaws) are the result of proto-Mongoloid/Caucasian admixture in Siberia. And the closest languages to the Japonic languages are Turkic.
The truth is that the Australoid is the dominant Asian phenotype. All Asians were Australoids until recently. The homeland of the Mongoloid race is in Northern Vietnam. This race was birthed 53,000 YBP. I am not sure what they looked like, but no doubt they were Australoids, possibly a Melanesian type. The Mongoloid phenotype we are so familiar with emerged quite late, 15,000 YBP in Siberia and 9,000 YBP in Northern China. Later it become generalized throughout Asia, moving from north to south.
It is true that in SE Asians, the transition occurred quite late. Vietnamese only transitioned from Australoid to Mongoloid 2,300 YBP with a massive invasion from Southern China. In some groups such as Malays, Filipinos, and Indonesians, the transition was not 100% completed. They are all Mongoloid people, but as the transition from Australoid to Mongoloid was not completed, some Australoid traits remain. These types are best seen as Mongoloids with some residual Australoid traits.
Clearly there are still some pure Australoids in SE Asia such as various Negrito peoples of Malaysia, Thailand (the Mani), the Philippines (the Agta) and Indonesia and the Senoi of Thailand, but these are the minority.
Indeed, Tamil (Dravidian) skulls from South India plot with Melanesian, Papuan, Aborigine, Negrito, Ainu, and Senoi skulls. Therefore on skulls, Tamil types are Australoids. The tribal types such as the Panyers, the Gondis and the Veddoids look very Australoid and probably represent the remnants of a derived group of the earliest Australoid settlers to India. The true first colonists of India are represented by the Andaman Islander Negrito types who came a very long time ago, possibly 40-50,000 YBP.
I have never heard the theory about tone languages deriving from African languages before.
Indeed there was some interbreeding between far NE Asians and Caucasoids. But also keep in mind that when you cross an Australoid with a Mongoloid, you sometimes coincidentally get a phenotype that looks Caucasoid. The early Samurai in Japan often appeared quite Caucasoid.
I agree that the Japonic languages are part of Altaic of which Turkic is a part, but Linguistics has not yet accepted this.