Telugu, Kannada, Malayalam and Tamil are related languages belonging to one Dravidian family, so if you speak Kannada already, it will be easier for you to learn Telugu, for example, and vice versa. Together with another 20 languages, they have evolved from a common ancestral language labeled as Proto-Dravidian.
EARLY SOUTHERN INDIANS
Early Indians were the aboriginal tribes, who spoke various Austro-Asiatic languages. They were the original hunter-gatherers of Southern India, who were assimilated into the mainstream population. These people have left their foot prints among all South Indian languages.
All Dravidian languages still share a common word for hunting derived from Veddah tribe (veta in Telugu). South India was populated by several such Austro-Asiatic tribes. Many of our words for flora and fauna have Austro-Asiatic origins
New Immigrants to Southern India
Around 2,500 BCE, these Austro-Asiatic people were gradually displaced by a new culture. Unlike the hunter-gatherers, these new comers were semi-nomads and animal herders, probably cultivated jowar, ragi, bajra like millets as well.
Their earliest pottery and ground axes in South India date to 3,000 BCE. There is archaeo-botanical evidence for cultivation, from 2,200 BCE, while they probably domesticated cattle, sheep and goats before 2,600 BCE.
Ash Mound Culture
These semi-nomads have created their own unique culture, called the Ash Mound culture. A particularly distinctive aspect of this ancient culture are “ashmound” sites which consist of large heaped accumulations of ash and vitrified material, which are now generally accepted as having originated from burnt cattle dung.
The petroglyphs are works of rock art found in Anantapur, Kurnool of AP and Bellary districts of Karnataka, India. Thousands of petroglyphs have been found, which date to the neolithic or even the old stone age.
ORIGIN OF DRAVIDIAN LANGUAGES
Ancestors to Ash Mound people spoke a common language labeled as Proto-Dravidian. These ancestors came to South India as a small band of nomads and initially settled along lower Godavari basin. The river name itself has Dravidian origins.
The lower Godavari Dravidian Home land hypothesis was originally proposed by Prof. F C Southworth (University of Pennsylvania). The Dravidian homeland is assumed to be the region with a maximum diversity of Dravidian languages. Because both in genetics as well as linguistics, geographical region with maximum diversity is assumed to be the origin. The rationale is based on the dynamics of population migrations.
The red outlined region (above) has the maximum diversity of Dravidian languages and hence it is the most probable origin of Proto-Dravidian language. Please read, Urheimat – Wikipedia. Oldest languages are closest to lower Godavari basin, around the red outlined region.
Now there is independent confirmation from genetic evidence. There is a high frequency of rare Haplogroup-T in coastal Andhra as well as the Horn-of-Africa. This rare haplogroup-T is associated with the neolithic farmers of Mesopotamia. For details please read, Genetics and the Afro-Dravidian Hypothesis
Geographical Expansion
As the population increased, proto-Dravidians began to expand into the neighboring regions. Ancient migrations are known to take place along the river routes because the rivers were the source of livelihood for these semi-nomads, so they expanded progressively and settled along river banks of Godavari, Krishna, Tungabadra and Kaveri and spread out into farthest corners of Southern India . Others have expanded upstream Godavari into Maharashtra and further into Gujarat.
Zdenek Burian: A neolithic settlement
Those who settled along lower Krishna basin became the ancestors to TELUGU speakers. Next, those who expanded westwards along the upper Krishna and Tungabadra into Karnataka became the ancestors to KANNADA speakers. Those who expanded further west became MALAYALAM speakers and finally those who expanded along the Kaveri river became the ancestors to TAMILS.
Dravidian migration along the river routes from Andhra to Karnataka to Kerala and finally Tamil Nadu. Image source: South India Fertility Project
As they expanded, they got geographically isolated from each other and came into contact Austro-Asiatic tribes. Their languages evolved into different dialects that ultimately became distinct languages.
CONCLUSIONS
Proto-Dravidian speakers first settled along the lower Godavari basin, next they further expanded along the river routes of Krishna, Tungabadra and Kaveri, gradually displacing the aboriginal Austro-Asiatic tribes. TELUGU ancestors settled along the lower Krishna basin to emerge as a distinct language. Others have further expanded along upper Krishna into Karnataka, westwards to reach Kerala, then southwards along the Kaveri to reach Tamil Nadu. Isolated from each others by mountain ranges and forests, KANNADA, MALAYALAM and TAMIL became distinct languages. Lower Godavari homeland is genetically associated with the Neolitihic farmers from Mesopotamia, as found from the high occurrence of Y-DNA haplogroup-T in coastal Andhra.