Theory:

The phase that followed the Neolithic is called the Iron Age or Megalithic period. During this period, people started using various metals but predominantly iron. However, they used iron predominantly, the evidence available for the usage of shell ornaments, carnelian and quartz beads.
 
People had metallurgical knowledge in iron, bronze and gold and pottery making. The Sangam age laid its foundation during this time. Various archaeological sites like Adhichanallur in Thoothukudi district, Sanur near Maduranthakam and Sithannavasal near Pudukkottai have disclosed the association of the Iron Age.
Lemuria and the Tamils 
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Submerged continent of Lemuria
 
Lemuria, the submerged continent, was assumed to be present below Tamil Nadu and covering Sri Lanka. During the 19th century, the progressions in plate tectonics theory, differing views are put forth by scholars and debate on Lemuria. Great Sangam literature like Silapathikaram, Manimekalai talks about the Lemuria continent and its territories. The Sangam literary references reveal to us that before 5000 years BC (BCE), Kanyakumari, Sri Lanka and Tamil Nadu were inter-connected by landmasses. Due to sea-level rise, there is partial submergence of land in and around Kanyakumari and the coast of India. Archaeological research reveals that a section of people from Mesolithic and Neolithic might have been living continuously in South India.
Megalithic Burial Types
We find burials with large stones for the mortal remains of the dead people. The skeletons or a few bones of the deceased were placed along with grave articles such as iron objects, carnelian beads and bronze objects in the burial sites. People who lived during this time might have believed that those tools and weapons would be helpful in the afterlife, so they placed these tools and objects along with the mortal remains(bones). Egyptian pyramids and Sangam Age burials also have similar artefacts. There are some of the burials which contain only the grave articles that are called, Memorial burials. Literatures belonging to the Sangam Age mentioned various burial practices of the people. Burials belonging to the megalithic period can be classified as dolmens, cists, menhirs, rock-cut caves, urn burials and sarcophagus.
 
The other types of burial are found in Kerala are as follows: Kodakkal (umbrella stone), Toppikkal (hat stone) and Paththikal (hood stone).
 
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Many burial customs observed during the megalithic age. Dolmens are table-like stone structures erected as monuments in burial grounds. Cists are stone slabs enclosures placed under the dig on its sides. On top of it, a big stone placed to make it look like a box. Portholes are holes used as a passage to go inside of cists and dolmens. It is believed that the movement of the soul or spirit uses this passage. The dead ancestors’ bodies were kept inside of Urns (pottery jars) and buried under the earth’s surface. Sarcophagi are terracotta containers with multiple legs, were also used for burial.
 
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Cist, Kodumanal
 
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Burial Urn, Adichanallur
 
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Kodakkal, toppikkal, Paththikal Kerala
 
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Burial Site, Arikkamedu
 
Menhirs are pillar-like stones erected as part of the burials. It is a memorial stone erected for heroes. During Iron-age or just before that the practise of erection of Menhir took place.
Agriculture and Pastoralism
For livelihood, people who lived in the Iron Age practised agriculture and raised cattle and sheep. While forming, they used cattle. The agro-pastoral groups did farming and pastoralism simultaneously. Still, some of the groups took care of hunting and gathering. Part of Agriculture, they grow millets and rice as livestock production and involve some crop cultivation. Subsequently, many of the megalithic sites are found nearby rivers and water bodies. They had good irrigation management practices that lead to irrigation technology systems. Evidence of these technologies and rice grain are found in the megalithic sites like Adhichanallur in Thoothukudi district and Porunthal near Palani.
Iron Age Society and Polity
The society of this era had farming groups, herders and hunter-gatherers groups. Professionals like craft specialists, potters and blacksmiths were also part of the groups. Various groups of peoples (tribes), their lifestyles and diverse practices and customs can be perceived from the varying sizes of burial sites. Some of the groups had prearranged chiefdoms showing human social development. Chiefdoms are the root of contemporary social human civilisation and led to the idea of cultural evolution.
 
It is understood that chiefdoms are in-between tribalism and civilisation. It is a form of social organisation more than a tribe or groups and less than a state or a civilisation. This period also witnessed wars due to cattle lifting, invasion and expansion of the other group’s territories. Group’s chiefdom led to succeeding kingdoms and modern country governments.
Pottery
The Iron and Sangam age people used pot for their food preparation, dining, storage, ornamentation and burial. Pottery is one of the important articles found in most archaeological sites. The potteries found were mostly in black and red colours. These mud pots are called as black ware and red ware pottery which means the raw material used in pottery gives the colours of the end product. The black and red ware has lustrous surfaces.
 
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Red & Black Pots from Adichanallur
Iron Technology and Metal Tools
The megalithic burial sites have plenty of iron objects that revealed that the people of this age used iron technology to make their tools. Swords and daggers, axes, chisels, lamps and tripod stands are found with wooden handle assemblage in these sites. They used these tools for various purposes such as farming, hunting, gathering, and battle. Bronze bowls, mirrors, bells and vessels decorated with beasts and birds at their apex were also excavated from the burial sites.
 
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Iron Knives, Adichanallur
Reference:
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https://archaeologynewsnetwork.blogspot.com/2015/02/more-on-iron-age-urns-excavated-in.html#.VOk8lE33-iw
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