Theory:

The phase that followed by the Neolithic is called the Iron Age or megalithic period. During this period people started using various metals but predominantly as Iron. Though they used Iron predominantly there were evidences available for the usage of shell ornaments, carnelian and quartz beads.
 
People had metallurgical knowledge in iron, bronze and gold and pottery making. Consequently the foundation for the Sangam Age was laid in this time. Many parts of Tamil Nadu, archaeological excavations done at Adhichanallur in Thoothukudi district, Sanur near Maduranthakam and Sithannavasal near Pudukkottai were clearly disclosed the association of 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 in Lemuria. Great Sangam literatures like Silapathikaram, Manimekalai talk about the Lemuria continent and its territories. The Sangam literary references reveal us that before 5000 years BC (BCE), Kanyakumari to 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
In Megalithic Burial Types, they built 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 lived in that period of time might have believed that those tools and weapons  would be useful in the after-life so they placed those 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 as 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 (hatstone) and Paththikal (hoodstone).
 
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Many burial practises are followed during this megalith 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 is placed to make it 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 surface of the earth. Sarcophagi are terracotta containers that sometimes had multiple legs which were also used for burial. Kerala had unique burial types of Kodakkal (umbrella stone), Toppikkal (hatstone) and Paththikal (hoodstone).
 
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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 practiced agriculture and Cattle rising. For forming they used cattle. In Animal husbandry they grow cattle and sheep. The agro pastoral groups were doing farming and Pastoralism simultaneously. Some of the groups were taking 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 have 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. This is a root of contemporary social human civilisation and led to the ideas of cultural evolution. It is understood that chiefdoms are in-between tribalism and civilisation. It is a form of social organization more than a tribe or groups and less than a state or a civilization. This period also witnessed wars due to snatching of Cattles, 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, and ornamentation and also for burial. Pottery is one of the important articles found in most of the 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 which revealed that the Iron Age people used iron technology for making their tools. Swords and daggers, axes, chisels, lamps and tripod stands are found with wooden handle assemblage. These tools were used for agriculture, hunting, gathering and in battles. 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:
https://i.pinimg.com/originals/ae/9e/11/ae9e11930e584fa3431d9538b25e8ca6.jpg
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https://fl.thgim.com/migration_catalog/article23007748.ece/alternates/FREE_435/FL06TWOMENHIRS2https://pbs.twimg.com/media/C9tIgtJUIAE94tA.jpg
https://riponrabbithole.com/wp-content/uploads/2020/07/48432/some-more-burial-urns-found-at-adichanallur.jpg
https://upload.wikimedia.org/wikipedia/commons/8/89/Kudakkallu_Parambu.JPG
https://archaeologynewsnetwork.blogspot.com/2015/02/more-on-iron-age-urns-excavated-in.html#.VOk8lE33-iw
https://fl.thgim.com/magazine/825ctc/article30205127.ece/alternates/FREE_320/20050701000106505jpg
https://fl.thgim.com/magazine/g1n7ao/article30205126.ece/alternates/FREE_320/20050701000106504jpg