One of the long standing hypotheses of ancient history is that agriculture (and with it settled civilization) made its way to India from the Fertile Cresent to the Indus River Valley around 7,000 BCE. These people, sometimes called the Harappans, engaged in trade with Sumeria, used the same package of crops (wheat and barley) and domesticated animals as those found in the Near East, and used a language that is lost to us, despite inscriptions that may have been a written language which have not been decoded. This part of the hypothesis remains unshaken.
My bet is that the Harappans may have spoken a language descended from the now extinct languages of Elam (in the mountains East of Sumeria in what is now Iran) or Sumeria (in what is now Shi'ite Iraq). But, we may never know.
Another hypothesis is that Dravidian language speakers had a pre-Iron Age agricultural civilization in India prior to the arrival of Indo-Aryan invaders from the North around 1,500 BCE who were effective horse riding warriors, probably originating in an Indo-European language homeland between the Black Sea and the Caspian Sea who brought their religion and language (an early version of Hindu Sanskrit culture) to India. This hypothesis also remains unshaken.
A third hypothesis is that the Indus Valley Civilization provided a parent language and culture for the Dravidian culture that is now found in Southern and Eastern India. This hypothesis is increasingly coming under fire.
It now appears that pre-Iron Age farmers of the Indus Valley Civilization, who were one of the first groups to come into contact with the Indo-Aryan invaders from the North, were linguistically, culturally and agriculturally separate from their contemporaries, the Dravidians.
But, there is little evidence to suggest that the stone age agricultural civilization of the Austroasiatic speakers who migrated into India from Southeast Asia provided a source for Dravidian culture either. They didn't domestic crops that the Dravidians use, their languages are very distinct from Dravidian languages, and the isolated pockets of Austroasiatic speakers today suggest that the bronze age Dravidian farmers conquered once much more widely distributed Austroasiatic stone age farmers.
So where did they come from?
In a story every bit as amazing of the colonization of Madagascar from Indonesia thousands of miles to the East, there is increasing evidence that the Dravidian culture of South India had its source in the Sahel farmers of West Africa, thousands of miles to the West at about the same latitude.
Historical records suggest that the South Dravidian language group had separated from a Proto-Dravidian language no later than 700 BCE, and linguistic evidence suggests that they probably became distinctive around 1,100 BCE, and some scholars using linguistic methods put the deepest divisions in the language group at roughly 3,000 BCE. Russian linguist M.S. Andronov puts the split between Tamil (a written Southern Dravidian language) and Telugu (a written Northern Dravidian language) at 1,500 BCE to 1,000 BCE.
Southworth, identifies late Proto-Dravidian with the Southern Neolithic culture in the lower Godavari River basin of South Central India, which first appeared ca. 2,500 BCE, based upon its agricultural vocabulary, while noting that this "would not preclude the possibility that speakers of an earlier stage of Dravidian entered the subcontinent from western or central Asia, as has often been suggested." . . .
French anthropologist Bernard Sergent, in La Genèse de l'Inde (1997), argued in 1997 that Dravidian language and culture has its roots in West Africa arriving in coastal West India around 2,500 BCE as a culture distinct from and contemporaneous with the Indus Valley Civilization. In this view, Dravidian is an offshoot of the Niger-Congo languages (sometimes called the Niger-Kordofanian) and of the Mande languages sometimes linked with them. In addition to linguistic similarities he points to other cultural connections such as similarities in musical instruments, matrilineal lineages, a shared game, acceptance of cousin marriage, and the use of rounded huts. Upadhyaya and Upadhyaya agree regarding the linguistic connections which they observed as early as 1976, as does C. Winters, on the basis of linguistic, and crop genetics evidence.
From Wikipedia (citations in the original omitted, written by me).
West African Sahel crops like sorghum and pearl millet which grow relatively warm climates with wet summers, thrive in Southern India, which has a similar climate, and arrive in India during the Southern Neolithic period. In contrast, crops domesticated in the Fertile Cresent, which appear in South Asia much earlier (from 7,000 BCE) in the Indus Valley region, which is further North. The shared game is mancala, a game that my children learned at school.
Harvard linguist Michael Witzel also makes the case that early Rigvedic Sanskrit, associated with the Indo-Aryan entry from the North into South Asia from ca. 1,500 BCE to 1,200 BCE in region that would have overlapped mostly with the Indus Valley Civilization, doesn't show Dravidian linguistic influences, and there is evidence than an isolated pocket of Dravidian speakers in Pakistan has a recent origin rather than reflecting an ancient wide distribution.
North India wouldn't have been an attractive place for farmers adapted to West African style agriculture who hadn't had time for their crops to adjust to a new environment to settle, but may have been more attractive for Indus Valley civilization stone age farmers using a Fertile Cresent agricultural package, and/or stone age Austro-Asiatic farmers ultimately tracing their roots to South China. Also, these two stone age farming populations may have had cultural exchanges that could have influenced the languages spoken at the boundary of the Indus River Valley civilization at the eastern headwaters of the Indus River, where the early Indo-Aryan invaders would have burst onto the scene.
The Southern Neolithic sites also have some copper artifacts, but not artifacts of other metals, consistent with the state of West African metallurgy around 2,500 BC. Sahel farmers may have felt pressure from both the South, as Bantu expansion posed a potential threat, and the North from the expanding Sahara Desert, at the time.
Some of these dots related to crop evidence weren't connected until up and coming archaeobotanist Dorian Q. Fuller made them.
Other Potential West African influences
Another group of linguistic suggestions is also interesting. One of the very distinct and near defining features of the Niger-Congo languages spoken in West Africa is that they have "noun classes". In many more familiar languages to English speakers, like French nouns have to agree in gender and number. In Niger-Congo languages, and a small number of other languages, there are distinctions beyond gender and number that are part of their grammar, like distinctions between living and non-living things.
This distinction is also made in the languages of the Caucuses, which have been fiercely resistant to outside influences, and in the Na-Dene languages which include an almost extinct language family found just to the West of the Bering Strait, many of the indigenous languages of Southern Alaska, and the Navajo language of the Southeast. It is also made in a moribund language of the Aboriginal Australians.
The Caucuses are a not implausible source for ancient Northern Siberian languages and a connection to the languages of the Caucuses had been suggested for the Northern Siberian languages now considered part of the Na-Dene languages before that connection was established. The Caucuses are also near the formative area for the Uralic languages (most famously Finnish) which show some similarity to Dravidian.
The same language of the Aboriginal Australians which has noun classes (like many Australian Aboriginal languages) also has a "mother-in-law language," i.e. a different speech register for use in the presence of mothers-in-law and certain other taboo relatives. There are two other vary notable language families where this is found. One is in some North American indignenous languages. Another is in Bantu, the dominant Niger-Congo language with roots in West Africa (Bantu also has Khoisan substrate language influences, for example incorporating click sounds in some areas).
Aboriginal Australians are believed to have arrived rather directly from Africa via Ethiopia and then a "Southern route" along the Indian ocean coast to Australia in a time period probably between 60,000 years ago and 50,000 years ago, providing a basis for a connection to early West African languages.
A West African linguistic connection to the Caucuses would support the apparent similarities between Dravidian and the Uralic languages (most prominently Finnish), even if the exact connection (from Africa to the Caucuses to the Urals, or from Africa to Southern India to the Caucuses to the Urals, for example) is not known.
Afro-centric educators have been pushing the case for West African cultural influences on the rest of the world for decades, mostly focusing on the often not very solid case of Egypt whose influences are much more strongly Ethiopian and Near Eastern in origin. Ironically, the influences appear to be in places they where far less expected: the place from which we draw the term that is the root for "Caucasian" (the anti-septic English language word for "white"), Finland, Southern India, Australia, Northern Siberia, Alaska, Western Canada, and the Navajo. This connected group of languages may even have been the immediate predecessor to the earliest Sino-Tibetan languages that ultimately gave rise to Chinese.
The linguistic connections other than Dravidian aren't as powerful since the total package of connections doesn't seem as great. But, opening up to the possibility of a West African-Dravidian connection makes the other potential links seem much more plausible than they might otherwise have seemed.